NCP4306 - Secondary Side Synchronous Rectification Driver ... · NCP4306 6 ABSOLUTE MAXIMUM RATINGS Table 3. ABSOLUTE MAXIMUM RATINGS Rating Symbol Value Unit Supply Voltage VCC −0.3

© Semiconductor Components Industries, LLC, 2017December, 2017 − Rev. 1

1 Publication Order Number:NCP4306/D

NCP4306

Secondary SideSynchronous RectificationDriver for High EfficiencySMPS Topologies

The NCP4306 is high performance driver tailored to control asynchronous rectification MOSFET in switch mode power supplies.Thanks to its high performance drivers and versatility, it can be used invarious topologies such as DCM or CCM flyback, quasi resonantflyback, forward and half bridge resonant LLC.

The combination of externally or fixed adjustable minimumoff-time and on-time blanking periods helps to fight the ringinginduced by the PCB layout and other parasitic elements. A reliable andnoise less operation of the SR system is insured due to the SelfSynchronization feature. The NCP4306 also utilizes Kelvinconnection of the driver to the MOSFET to achieve high efficiencyoperation at full load and utilizes a light load detection architecture toachieve high efficiency at light load.

The precise turn−off threshold, extremely low turn−off delay timeand high sink current capability of the driver allow the maximumsynchronous rectification MOSFET conduction time and enablesmaximum SMPS efficiency. The high accuracy driver and 5 V gateclamp enables the use of GaN MOSFETs.

Features

• Self−Contained Control of Synchronous Rectifier in CCM, DCM andQR for Flyback or LLC Applications

• Precise True Secondary Zero Current Detection• Typically 15 ns Turn off Delay from Current Sense Input to Driver• Rugged Current Sense Pin (up to 200 V)• Ultrafast Turn−off Trigger Interface / Disable Input (10.5 ns)• Adjustable or Fixed Minimum ON−Time• Adjustable or Fixed Minimum OFF-Time with Ringing Detection• Improved Robust Self Synchronization Capability• 7 A / 2 A Peak Current Sink / Source Drive Capability• Operating Voltage Range up to VCC = 35 V• Automatic Light−load Disable Mode• GaN Transistor Driving Capability• Low Startup and Disable Current Consumption• Maximum Operation Frequency up to 1 MHz• TSOP6 and SOIC-8 Packages• This is a Pb−Free Device

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SOIC−8 NBCASE 751−07

MARKING DIAGRAMS

Typical Applications

• Notebook Adapters• High Power Density AC / DC Power

Supplies (Cell Phone Chargers)• LCD TVs• All SMPS with High Efficiency

Requirements

TSOP−6 CASE 318G−02

1

8

XXXXX = Specific Device CodeA = Assembly LocationL = Wafer LotY = YearW = Work Week� = Pb−Free Package

XXXXXALYWX

�1

8

IC(Pb−Free)

XXXAYW��

1

(Note: Microdot may be in either location)

1

SOIC−8 NB TSOP−6

IC(Pb−Free)

See detailed ordering and shipping information on page 2 ofthis data sheet.

ORDERING INFORMATION

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NCP4306

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ORDERING INFORMATION TABLE

Table 1. AVAILABLE DEVICES

Device Package Package Marking Packing Shipping †

NCP4306AAAZZZADR2G SOIC8 6AAAZZZA SOIC−8(Pb−Free)

2500 / Tape and Reel

NCP4306AADZZZADR2G 6AADZZZA

NCP4306AAHZZZADR2G 6AAHZZZA

NCP4306DADZZDASNT1G TSOP6 6AC TSOP−6(Pb−Free)

3000 / Tape and Reel

NCP4306DAHZZAASNT1G 6AD

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel PackagingSpecification Brochure, BRD8011 / D.

See the ON Semiconductor Device Nomenclature document (TND310 / D) for a full description of the naming conventionused for image sensors. For reference documentation, including information on evaluation kits, please visit our web site atwww.onsemi.com.

Figure 1. Typical Application Example – LLC Converter with optional LLD and Trigger Utilization

+VBULK

LLCSTAGE

CONTROL

M1

M2 N1

C1

OK1

N3

N2

Tr1

R1 C3

+VOUT

RTN

D1

R2

C4

M4

M3

C2

NCP4306

VCCMIN_TOFF

MIN_TONLLD

DRV

GNDCS

TRIG

VCCMIN_TOFF

MIN_TONLLD

DRVGND

CSTRIG

NCP4306R

MIN

_TO

FF

RM

IN_T

ON

RLL

D

RM

IN_T

OF

F

RM

IN_T

ON

RLL

D

http://www.onsemi.com/http://www.onsemi.com/pub/Collateral/BRD8011-D.PDFhttp://www.onsemi.com/pub_link/Collateral/TND310-D.PDFhttp://www.onsemi.com/

NCP4306

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Figure 2. Typical Application Example – DCM, CCM or QR Flyback Converter with optional LLD and disabled TRIG

VBULK

FLYBACKCONTROLCIRCUITRY

M1

C1

OK1

R1

D3

C2

TR1

R3

M2

GNDC4

D5NCP4306

RM

IN_T

OF

F

RLL

D

R2

DRV

CSFB

VCC

C3D4

C5

MIN_TOFF

MIN_TON

LLD

+VOUTVBULK


M1

C1

OK1

R1

D3

C2

TR1

R3

M2

GNDC4

D5NCP4306

RM

IN_T

ON

RLL

D

R2

DRV

CSFB

VCC

C3D4

C5

VCC DRV

GND

CS

TRIG

+VOUT

Figure 3. Typical Application Example – DCM, CCM or QR Flyback Converter with NCP4306 in TSOP6 (v Cxxxxxx)

VBULK

C1 R1

D3

C2

TR1


M1DRV

CSFB

VCC

C3

OK1

M2D4

R3

C4GND

C5

D5NCP4306

RM

IN_T

OF

F

RLL

D

+VOUT

VCC

MIN_TOFF

LLD

GND

CS

DRV


NCP4306

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Figure 4. Typical Application Example – Primary Side Flyback Converter and NCP4306 in TSOP6

VBULK

C1R1

D3

C2

TR1

C6

M2

R5 C8

GND

+VOUT

C7

R3

R4

C5

C4R3

ZCD

C3

D4

VCC

DRV M1

R2

CSCOMP

VCC

MIN_TOFFGND

CS

DRV

MIN_TON

NCP4306

RM

IN_T

OF

F

RM

IN_T

ON

PRIMARYSIDE

FLYBACKCONTROLLER

PIN FUNCTION DESCRIPTION

Table 2. PIN FUNCTION DESCRIPTION

TSOP6Bxxxxxx

TSOP6Cxxxxxx

TSOP6Dxxxxxx

TSOP6Exxxxxx

TSOP6Fxxxxxx

TSOP6Gxxxxxx

SOIC8Axxxxxx

Pin Name Description

6 6 6 6 6 6 1 VCC Supply voltage pin

− 5 5 5 − 2 MIN_TOFF Adjust the minimum off timeperiod by connecting resistor toground

5 − 4 − 5 − 3 MIN_TON Adjust the minimum on timeperiod by connecting resistor toground

4 4 − − − 4 4 LLD This input modulates the driverclamp level and / or turns the driv-er off during light load conditions

− − − 4 4 5 5 TRIG / DIS Ultrafast turn−off input that can beused to turn off the SR MOSFETin CCM applications in order toimprove efficiency. Activatesdisable mode if pulled−up formore than 100 μs

3 3 3 3 3 3 6 CS Current sense pin detects if thecurrent flows through the SRMOSFET and / or its body diode

2 2 2 2 2 2 7 GND Ground connection for the SRMOSFET driver and VCCdecoupling capacitor. Groundconnection for minimum tON andtOFF adjust resistors, LLD andtrigger inputsGND pin should be wired directlyto the SR MOSFET sourceterminal / soldering point usingKelvin connection

1 1 1 1 1 1 8 DRV Driver output for the SR MOSFET


NCP4306

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Figure 5. Internal Circuit Architecture – NCP4306

Minimum ON timegenerator

MIN_TON

CSdetection

CS

MIN_TOFF

TRIG/DIS

DRV

VCC

GND

VCC managmentUVLO

DRIVER

VDD

LLDDisable detection

ELAPSED

EN

Minimum OFFtime generator

RESET

ELAPSED

Control logic

EN

DISABLE

Disable detection

DISABLE

DISABLETRIG

dV/dt

Exception timegenerator

ENELAPSED

10 μA VTRIG

DRVOUT

EXT_ADJ

INT_ADJ

EXT_ADJ

INT_ADJ

INT_ADJ

CS_ONCS_OFFCS_RESET


NCP4306

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ABSOLUTE MAXIMUM RATINGS

Table 3. ABSOLUTE MAXIMUM RATINGS

Rating Symbol Value Unit

Supply Voltage VCC −0.3 to 37.0 V

TRIG / DIS, MIN_TON, MIN_TOFF, LLD Input Voltage (Note 3) VTRIG / DIS, VMIN_TON, VMIN_TOFF, VLLD −0.3 to VCC V

Driver Output Voltage VDRV −0.3 to 17.0 V

Current Sense Input Voltage VCS −4 to 200 V

Current Sense Dynamic Input Voltage (tPW = 200 ns) VCS_DYN −10 to 200 V

MIN_TON, MIN_TOFF, LLD, TRIG Input Current IMIN_TON, IMIN_TOFF, ILLD, ITRIG −10 to 10 mA

DRV Pin Current (tPW = 10 μs) IDRV_DYN −3 to 12 A

VCC Pin Current (tPW = 10 μs) IVCC_DYN 3 A

Junction to Air Thermal Resistance, 1 oz 1 in2 Copper Area,SOIC8

RθJ−A_SOIC8 200 °C / W

Junction to Air Thermal Resistance, 1 oz 1 in2 Copper AreaTSOP6

RθJ−A_TSOP6 250 °C / W

Maximum Junction Temperature TJMAX 150 °C

Storage Temperature TSTG −60 to 150 °C

ESD Capability, Human Body Model (except pin CS) (Note 1) ESDHBM 2000 V

ESD Capability, Human Body Model Pin CS ESDHBM 600 V

ESD Capability, Machine Model (Note 1) ESDMM 200 V

ESD Capability, Charged Device Model (Note 1) ESDCDM Class C1 -

Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionalityshould not be assumed, damage may occur and reliability may be affected.1. This device series contains ESD protection and exceeds the following tests:

Except pin CS: Human Body Model 2000 V per JEDEC Standard JESD22−A114E.All pins: Machine Model Method 200 V per JEDEC Standard JESD22−A115−ACharged Machine Model per JEDEC Standard JESD22−C101F

2. This device meets latchup tests defined by JEDEC Standard JESD78D.3. If voltage higher than 22 V is connected to pin, pin input current increases. Internal ESD clamp contains 24 V Zener diode with 3 kΩ in series.

It is recommended to add serial resistance in case of higher input voltage to limit input pin current.

Table 4. RECOMMENDED OPERATING CONDITION

Parameter Symbol Min Max Unit

Maximum Operating Voltage VCC 35 V

Operating Junction Temperature TJ −40 125 °C


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ELECTRICAL CHARACTERISTICS

Table 5. ELECTRICAL CHARACTERISTICS −40 ºC ≤ TJ ≤ 125 ºC; VCC = 12 V; CDRV = 0 nF; RMIN_TON = RMIN_TOFF = 10 kΩ or internally set values; VLLD = 3.0 V or LLD internallydisabled; VTRIG / DIS = 0 V; VCS = 4 V, unless otherwise noted. Typical values are at TJ = +25 ºC

Parameter Test Conditions Symbol Min Typ Max Unit

SUPPLY SECTION

VCC UVLO VCC rising VCCON 3.7 4.0 4.2 V

VCC falling VCCOFF 3.2 3.5 3.7

VCC UVLO Hysteresis VCCHYS 0.5 V

Start−up Delay VCC rising from 0 to VCCON + 1 V @ tr= 10 μs

tSTART_DEL 50 80 μs

Current Consumption,tMIN_TON = tMIN_TOFF = 1 μs, tLLD = 130 μs

CDRV = 0 nF,fCS = 100 kHz

xAxxxxx ICC 1.8 2.5 mA

xBxxxxx 1.7 2.4


xAxxxxx 2.8 4.0

xBxxxxx 2.1 3.4


xAxxxxx 12 15

xBxxxxx 6.7 9.0

Current Consumption ICC 1.4 2.2 mA

Current Consumption below UVLO VCC = VCCOFF – 0.1 V ICC_UVLO 35 60 μACurrent Consumption in Disable Mode t > tLLD , VLLD = 0.55 V ICC_DIS 60 100 μA

VTRIG / DIS = 5 V; VLLD = 0.55 V 60 100

t > tLLD, LLD set internally 37 80

VTRIG / DIS = 5 V, LLD set internally 37 80

DRIVER OUTPUT

Output Voltage Rise−Time CDRV = 10 nF, 10 % to 90 % VDRVMAX,VCS = 4 to −1 V

tr 60 100 ns

Output Voltage Fall−Time CDRV = 10 nF, 90 % to 10 % VDRVMAX,VCS = −1 to 4 V

tf 25 45 ns

Driver Source Resistance RDRV_SOURCE 2 Ω

Driver Sink Resistance RDRV_SINK 0.5 Ω

Output Peak Source Current IDRV_SOURCE 2 A

Output Peak Sink Current IDRV_SINK 7 A

Maximum Driver Pulse Length tDRV_ON_MAX 4 ms

Maximum Driver Output Voltage VCC = 35 V, CDRV > 1 nF, (ver. xAxxxxx)

VDRVMAX 9 10 11 V

VCC = 35 V, CDRV > 1 nF, (ver. xBxxxxx)

4.5 5.0 5.5

Minimum Driver Output Voltage VCC = VCCOFF + 200 mV, (ver. xAxxxxxx)

VDRVMIN 3.4 3.7 3.9 V

VCC = VCCOFF + 200 mV, (ver. xBxxxxxx)

3.4 3.7 3.9

CS INPUT

Total Propagation Delay From CS toDRV Output On

VCS goes down from 4 to −1 V,tf_CS

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Table 5. ELECTRICAL CHARACTERISTICS (continued)−40 ºC ≤ TJ ≤ 125 ºC; VCC = 12 V; CDRV = 0 nF; RMIN_TON = RMIN_TOFF = 10 kΩ or internally set values; VLLD = 3.0 V or LLD internallydisabled; VTRIG / DIS = 0 V; VCS = 4 V, unless otherwise noted. Typical values are at TJ = +25 ºC

Parameter UnitMaxTypMinSymbolTest Conditions

CS INPUT

dV / dt Detector Low Threshold VCS_DVDT_L 0.5 V

dV / dt Detector Threshold (Note 4) ver. xxDxxxx tdV / dt 13 25 37 ns

TRIGGER DISABLE INPUT

Minimum Trigger Pulse Duration VTRIG / DIS = 5 V; Shorter pulses maynot be proceeded

tTRIG_PW_MIN 10 ns

Trigger Threshold Voltage VTRIG_TH 1.6 2.0 2.2 V

Trigger to DRV Propagation Delay VTRIG / DIS goes from 0 to 5 V, tr_TRIG / DIS

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Table 5. ELECTRICAL CHARACTERISTICS (continued)−40 ºC ≤ TJ ≤ 125 ºC; VCC = 12 V; CDRV = 0 nF; RMIN_TON = RMIN_TOFF = 10 kΩ or internally set values; VLLD = 3.0 V or LLD internallydisabled; VTRIG / DIS = 0 V; VCS = 4 V, unless otherwise noted. Typical values are at TJ = +25 ºC

Parameter UnitMaxTypMinSymbolTest Conditions

LLD ADJUST

LLD Reduced Time Disable mode activated tLLD_RED 0.5 ×tLLD

μs

LLD Blanking Time tLLD_BLK 0.25 ×tLLD

μs

Disable Recovery Time tMIN_TOFF = 130 ns tLLD_DIS_REC 1.5 3.0 μs

EXCEPTION TIMER

Exception Time (ver. xxHxxxx) tEXC 4 ×tMIN_TON

μs

Exception Timer Ratio Accuracy RatioEXC −15 +15 %

4. Test signal:

VCS [V]

4.0

1.5

−1.0t [ns]

t dV/dt

VCS_DVDT_H

VCS_DVDT_L

Figure 6. Test Signal


NCP4306

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TYPICAL CHARACTERISTICS

3,3

3,4

3,5

3,6

3,7

3,8

3,9

4,0

4,1

4,2

−40 −20 0 20 40 60 80 100 120

VCC on

VCC off

Figure 7. VCCON and VCCOFF Levels

TJ[°C]

VC

C[V

]

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

0 5 10 15 20 25 30 35

TJ = 125 °CTJ = 85 °CTJ = 55 °CTJ = 25 °CTJ = 0 °CTJ = −20 °CTJ = −40 °C

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

0 5 10 15 20 25 30 35

TJ = 125 °CTJ = 105 °CTJ = 85 °CTJ = 55 °CTJ = 25 °CTJ = 0 °CTJ = −20 °CTJ = −40 °C

Figure 8. Current Consumption VCS = 4 V

VCC[V]

I CC

[mA

]

Figure 9. Current Consumption, fCS = 100 kHz, CDRV = 1 nF, Ver. xAxxxxx

Figure 10. Current Consumption, fCS = 100 kHz, Ver. xAxxxxx

VCC[V]

I CC

[mA

]

0

2

4

6

8

10

12

14

−40 −20 0 20 40 60 80 100 120

CDRV = 0 nF

CDRV = 1 nF

CDRV = 10 nFI CC

[mA

]

TJ[°C]

0,0

0,5

1,0

1,5

2,0

2,5

0 5 10 15 20 25 30 35

Figure 11. Current Consumption, fCS = 100 kHz, Ver. xBxxxxx

0

1

2

3

4

5

6

7

8

9

10

−40 −20 0 20 40 60 80 100 120

Figure 12. Current Consumption, fCS = 100 kHz, CDRV = 1 nF, Ver. xBxxxx

I CC

[mA

]

TJ[°C]

I CC

[mA

]

VCC[V]

TJ = 125 °CTJ = 105 °CTJ = 85 °CTJ = 55 °CTJ = 25 °CTJ = 0 °C



CDRV = 0 nF

CDRV = 1 nF

CDRV = 10 nF


NCP4306

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0

10

20

30

40

50

60

−40 −20 0 20 40 60 80 100 12020

30

40

50

60

70

80

90

100

−40 −20 0 20 40 60 80 100 120

Figure 13. Current Consumption below UVLO, VCC = VCCOFF − 0.1 V

TJ[°C]

I CC

_UV

LO[μ

A]

I CC

_DIS

[μA

]

TJ[°C]

Figure 14. Current Consumption in Disable ModeVCS = 4 V, t > tLLD

20

30

40

50

60

70

80

90

100

−40 −20 0 20 40 60 80 100 1200

20

40

60

80

100

120

0 5 10 15 20 25 30 35

Figure 15. Current Consumption in Disable Mode,VTRIG/DIS = 5 V

Figure 16. Current Consumption in Disable Mode,VCS = 4 V, t > tLLD

20

30

40

50

60

70

80

90

100

0 5 10 15 2025

30 35−1,0

−0,9

−0,8

−0,7

−0,6

−0,5

−0,4

−0,3

−0,2

−0,1

0,0

−1 −0,8 −0,6 −0,4 −0,2 0 0,2 0,4 0,6 0,8 1

Figure 17. Current Consumption in Disable Mode,VTRIG/DIS = 5 V

Figure 18. CS Input Current

I CC

_DIS

[μA

]

I CC

_DIS

[μA

]

I CC

_DIS

[μA

]

I CS[m

A]

TJ[°C] VCC[V]

VCS[V]VCC[V]

TJ = 125 °CTJ = 105 °CTJ = 85 °CTJ = 55 °C

TJ = 25 °CTJ = 0 °CTJ = −20 °CTJ = −40 °C

TJ = 125 °CTJ = 105 °C

TJ = 85 °CTJ = 55 °CTJ = 25 °CTJ = 0 °CTJ = −20 °CTJ = −40 °C




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Figure 19. Supply Current vs. CS Voltage

−120

−110

−100

−90

−80

−70

−60

−50

−40

−40 −20 0 20 40 60 80 100 1200,00,20,40,60,81,01,21,41,61,82,02,2

−1,0 −0,8 −0,6 −0,4 −0,2 0,0 0,2 0,4 0,6 0,8 1,0

Figure 20. CS Turn−on Threshold

I CC

[mA

]

VCS[V]

VT

H_C

S_O

N[m

V]

TJ[°C]

−2,0

−1,5

−1,0

−0,5

0,0

0,5

1,0

−40 −20 0 20 40 60 80 100 1200,40

0,45

0,50

0,55

0,60

−40 −20 0 20 40 60 80 100 120

0

100

200

300

400

500

−40 −20 0 20 40 60 80 100 12010

15

20

25

30

35

40

45

50

55

60

−40 −20 0 20 40 60 80 100 120

Figure 21. CS turn−off Threshold Figure 22. CS Reset Threshold

Figure 23. CS Input Leakage VCS = 200 V Figure 24. Propagation Delay from CS to DRV Output On

TJ[°C]

TJ[°C]

TJ[°C]

TJ[°C]

VT

H_C

S_O

FF[m

V]

VT

H_C

S_R

ES

ET[V

]

I CS

_LE

AK

AG

E[n

A]

t PD

_ON

[ns]



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Figure 25. Propagation Delay from CS to DRV Output Off

4

6

8

10

12

14

16

18

20

22

24

−40 −20 0 20 40 60 80 100 120

Figure 26. Trigger Pin Threshold

1,0

1,2

1,4

1,6

1,8

2,0

2,2

0 5 10 15 20 25 30 35

TJ[°C]

t PD

_OF

F[n

s]

VCC[V]

VT

RIG

_TH

[V]

1,7

1,8

1,9

2,0

2,1

2,2

2,3

−40 −20 0 20 40 60 80 100 1207

8

9

10

11

12

13

14

15

−40 −20 0 20 40 60 80 100 120

Figure 27. Trigger Pin Threshold Figure 28. Trigger Pin Pull Down Current

3

5

7

9

11

13

15

17

−40 −20 0 20 40 60 80 100 120

TJ[°C] TJ[°C]

TJ[°C]

Figure 29. Propagation Delay from TRIG to DRV Output Off

Figure 30. Delay to Disable Mode, VTRIG/DIS = 5 V

VT

RIG

_TH

[V]

I TR

IG/D

IS[μ

A]

t PD

_TR

IG[n

s]

80

85

90

95

100

105

110

115

120

−40 −20 0 20 40 60 80 100 120

t DIS

_TIM

[μs]

TJ[°C]




NCP4306

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Figure 31. Minimum on Time RMIN_TON = 10 k�

0,90

0,92

0,94

0,96

0,98

1,00

1,02

1,04

1,06

1,08

1,10

−40 −20 0 20 40 60 80 100 1204,5

4,6

4,7

4,8

4,9

5,0

5,1

5,2

5,3

5,4

5,5

−40 −20 0 20 40 60 80 100 120

Figure 32. Minimum on Time RMIN_TON = 50 k�

0,90

0,92

0,94

0,96

0,98

1,00

1,02

1,04

1,06

1,08

1,10

−40 −20 0 20 40 60 80 100 1204,4

4,5

4,6

4,7

4,8

4,9

5,0

5,1

5,2

5,3

5,4

−40 −20 0 20 40 60 80 100 120

Figure 33. Minimum on Time RMIN_TOFF = 10 k� Figure 34. Minimum on Time RMIN_TOFF = 50 k�

−25,0

−20,0

−15,0

−10,0

−5,0

0,0

0 5 10 15 20 25 30 35

Figure 35. LLD Current, VLLD = 3.0 V Figure 36. LLD current, VLLD = 2.5 V

TJ[°C]

t MIN

_TO

N[μ

s]t M

IN_T

OF

F[μ

s]I L

LD[μ

A]

TJ[°C]

t MIN

_TO

N[μ

s]

TJ[°C]TJ[°C]

VCC[V]

t MIN

_TO

FF[μ

s]



−22,0

−21,5

−21,0

−20,5

−20,0

−19,5

−19,0

−18,5

−18,0

0 5 10 15 20 25 30 35

I LLD

[μA

]

VCC[V]

TJ = 125 °CTJ = 105 °CTJ = 85 °CTJ = 55 °C

TJ = 25 °CTJ = 0 °CTJ = −20 °CTJ = −40 °C


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Figure 37. LLD Current Figure 38. LLD Time, VLLD = 1.82 V (or Internal Option)

440

460

480

500

520

540

560

580

600

620

640

−40 −20 0 20 40 60 80 100 1200 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

−15.0

−16.0

−17.0−18.0−19.0

−20.0

−21.0−22.0

−23.0

−24.0

−25.0

VLLD[V]

I LLD

[μA

]

TJ[°C]

t LLD

[μs]

9,0

9,2

9,4

9,6

9,8

10,0

10,2

10,4

−40 −20 0 20 40 60 80 100 120

VCC = 12 V, CDRV = 0 nFVCC = 12 V, CDRV = 1 nFVCC = 12 V, CDRV = 10 nFVCC = 35 V, CDRV = 0 nFVCC = 35 V, CDRV = 1 nFVCC = 35 V, CDRV = 10 nF

4,3

4,5

4,7

4,9

5,1

5,3

5,5

−40 −20 0 20 40 60 80 100 120

VD

RV[V

]

TJ[°C] TJ[°C]

VD

RV[V

]

13

18

23

28

33

38

−40 −20 0 20 40 60 80 100 120

Figure 39. Driver Output Voltage, Ver. xAxxxxx Figure 40. Driver Output Voltage, Ver. xBxxxxx

3,4

3,6

3,8

4,0

4,2

4,4

4,6

−40 −20 0 20 40 60 80 100 120

Figure 41. dV/dt Detector Time Threshold, Ver. xxDxxxx

Figure 42. Exception Timer Ratio to tMIN_TON, Ver. xxHxxxx

TJ[°C] TJ[°C]

t dV

/dt[n

s]

Rat

ioE

XC

[−]


VCC = 12 V, CDRV = 0 nFVCC = 12 V, CDRV = 1 nFVCC = 12 V, CDRV = 10 nFVCC = 35 V, CDRV = 0 nFVCC = 35 V, CDRV = 1 nFVCC = 35 V, CDRV = 10 nF


NCP4306

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GENERAL DESCRIPTION

The NCP4306 is designed to operate either as a standaloneIC or as a companion IC to a primary side controller to helpachieve efficient synchronous rectification in switch modepower supplies. This controller features a high current gatedriver along with high−speed logic circuitry to provideappropriately timed drive signals to a synchronousrectification MOSFET. With its novel architecture, theNCP4306 has enough versatility to keep the synchronousrectification system efficient under any operating mode.

The NCP4306 works from an available voltage with rangefrom 4.0 / 3.5 V to 35 V (typical). The wide VCC rangeallows direct connection to the SMPS output voltage of mostadapters such as notebooks, cell phone chargers and LCDTV adapters.

Precise turn−off threshold of the current sense comparatortogether with an accurate offset current source allows theuser to adjust for any required turn−off current threshold ofthe SR MOSFET switch using a single resistor. Comparedto other SR controllers that provide turn−off thresholds inthe range of −10 mV to −5 mV, the NCP4306 offers aturn−off threshold of 0 mV. When using a low RDS_ON SR(1 mΩ) MOSFET our competition, with a −10 mV turn off,will turn off with 10 A still flowing through the SR FET,while our 0 mV turn off turns off the FET at 0 A;significantly reducing the turn−off current threshold andimproving efficiency. Many of the competitor partsmaintain a drain source voltage across the MOSFET causingthe SR MOSFET to operate in the linear region to reduceturn−off time. Thanks to the 6 A sink current of theNCP4306 significantly reduces turn off time allowing for aminimal drain source voltage to be utilized and efficiencymaximized.

To overcome false triggering issues after turn−on andturn−off events, the NCP4306 provides adjustable minimum

on−time and off−time blanking periods. Blanking times canbe set internally during production or adjustedindependently of IC VCC using external resistors connectedto GND (internal or external option depends on IC variant).If needed, externally set blanking periods can be modulatedusing additional components.

An extremely fast turn−off comparator, implemented onthe current sense pin, allows for NCP4306 implementationin CCM applications without any additional components orexternal triggering.

An ultrafast trigger input offers the possibility to furtherincrease efficiency of synchronous rectification systemsoperated in CCM mode (for example, CCM flyback orforward). The time delay from trigger input to driver turn offevent is tPD_TRIG. Additionally, the trigger input can be usedto disable the IC and activate a low consumption standbymode. This feature can be used to decrease standbyconsumption of an SMPS. If the trigger input is not wantedthan the trigger pin can be tied to GND.

An output driver features capability to keep SR transistorturned−off even when there is no supply voltage for theNCP4306. SR transistor drain voltage goes up and downduring SMPS operation and this is transferred through draingate capacitance to gate and may open transistor. TheNCP4306 keeps DRV pin pulled low even without anysupply voltage and thanks to this the risk of turned−on SRtransistor before enough VCC is applied to the NCP4306 iseliminated.

Finally, the NCP4306 features a Light Load Detectionfunction that can be set internally or externally at LLD pinby resistor connected to ground. This function detects lightload or no load conditions and during them betweenconduction phases it decreases current consumption. Thishelps to improve SMPS efficiency. If LLD function is notneeded pin can be left open.


NCP4306

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SUPPLY SECTION

Supply voltage should be connected to VCC pin.Minimum voltage for proper operation is 4.0 / 3.5 Vtypically and maximum level is 35 V. Decoupling capacitorbetween VCC and GND pin is needed for proper operationand its recommended value is 1 μF. If IC is supplied fromSMPS output voltage, few ohm resistor is recommendedbetween SMPS output voltage and VCC pin. Resistor taskis to divide decoupling cap from output to avoid closing HFcurrents through NCP4306 decoupling cap, because thesecurrents may causes drops at GND connection that affectsSR transistor sensing and incorrect SR transistor turn−off.

SR transistor is usually used in low side configuration(placed in return path), but it may be also used in high sideconfiguration (placed in positive line). It is not possible touse SMPS VOUT for SR supply in high side configuration soit is needed to provide supply differently. One possibility isto use auxiliary winding as shown in Figure 43. Voltage fromauxiliary winding is rectified, filtered and use as supplyvoltage.

Figure 43. High Side Configuration Supplied from Auxiliary Winding

C1

GND

+VOUT

D5OK1

R3

M2

M1

R1CSFB

VCC

D1

DRVD2

C3

C1 R2 C2

D3

C5C4R6

D4TR1

R7R8R9

NCP4306


If auxiliary winding is not acceptable, transformerforward voltage can be used as supply source (Figure 44).Forward voltage is regulated by simple voltage regulator to

fit NCP4306 VCC restriction. Penalty for this solution isslightly lower efficiency.

Figure 44. High Side Configuration Supplied from Transformer Forward Voltage

VBULK

+VOUT

C1 R2 C2

FB CS

DRV D2

C3D1

D3

M1

R1

R3

OK1 D6 GND

C6

M2

D4 D5

R6 R7

C4 C5

R8R9

FLYBACKCONTROLL

NCP4306


NCP4306

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Auxiliary winding or forward voltage can be used assupply source also for low side configuration if VOUT is nothigh enough (Figure 45). Do not focus just on SR controller

UVLO, but also on SR transistor characteristics. Sometransistors may be not turned−on enough even at 5 V so inthese case SR controller supply voltage should be increased.

Figure 45. Low Side Configuration Supplied from Transformer Forward Voltage for Low VOUT SMPS

C6

R2R5

C5

C4R4

ZCD

R3C1

R1C2

D3

D4

C3

VCC

DRV M1

CSCOMP

VBULK

D4 R6

R7

M2 D5R8

C7

C8

+VOUT < 5V

GNDC9

NCP4306

PRIMARYSIDE

FLYBACKCONTROLLER

Current Sense InputFigure 46 shows the internal connection of the CS

circuitry on the current sense input. When the voltage on thesecondary winding of the SMPS reverses, the body diode ofM1 starts to conduct current and the voltage of M1’s draindrops approximately to −1 V. Once the voltage on the CS pinis lower than VTH_CS_ON threshold, M1 is turned−on.

Because of parasitic impedances, significant ringing canoccur in the application. To overcome false sudden turn−offdue to mentioned ringing, the minimum conduction time ofthe SR MOSFET is activated. Minimum conduction timecan be adjusted using the RMIN_TON resistor or can bechosen from internal fixed values.

Figure 46. Current Sensing Circuitry Functionality

SR MOSFET

+ VOUT

M1

To Internal logicCS_RESET

High dV / dt

CS_OFF

CS_ON

VTH_CS_RESET

dV / dtDetector

VTH_CS_ON

+


NCP4306

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The SR MOSFET is turned−off as soon as the voltage onthe CS pin is higher than VTH_CS_OFF (typically −0.5 mV).For the same ringing reason, a minimum off−time timer isasserted once the VCS goes above VTH_CS_RESET. Theminimum off−time can be externally adjusted usingRMIN_TOFF resistor or can be chosen from internally fixedvalues (depends on version). The minimum off−timegenerator can be re−triggered by MIN_TOFF resetcomparator if some spurious ringing occurs on the CS inputafter SR MOSFET turn−off event. This feature significantlysimplifies SR system implementation in flyback converters.

In an LLC converter the SR MOSFET M1 channelconducts while secondary side current is decreasing (refer toFigure 47). Therefore the turn−off current depends onMOSFET RDSON. The −0.5 mV threshold provides anoptimum switching period usage while keeping enough timemargin for the gate turn−off. To ensure proper switching, themin_tOFF timer is reset, when the VDS of the MOSFET ringsand falls down past the VTH_CS_RESET. The minimumoff−time needs to expire before another drive pulse can beinitiated. Minimum off−time timer is started again whenVDS rises above VTH_CS_RESET.

Figure 47. CS Input Comparators Thresholds and Blanking Periods Timing in LLC

VDS = VCS

ISEC

VTH_CS_RESET

VTH_CS_OFF

VDRV

Min ON−time

Min OFF−time

VTH_CS_ON

Turn on delay Turn off delay

tMIN_TON

tMIN_TOFF

Min tOFF timer wasstopped here because of

VCS

NCP4306

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Figure 48. CS Input Comparators Thresholds and Blanking Periods Timing in Flyback

VTH_CS_RESET

VTH_CS_OFF

VDRV

Min ON−time

Min OFF−time

VTH_CS_ON

Turn on delay Turn off delay

Min tOFF timer wasstopped here because of

VCS

NCP4306

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Figure 49. SR System Connection Including MOSFET and Layout Parasitic Inductances in a) LLC and b) FlybackApplication

VL_LAYOUT VL_DRAIN VRDS_ON VL_SOURCE VL_LAYOUT

ISECVDS

LLAYOUT

To VCC

LSOURCERDS_ONLDRAIN

MOSFET equivalent circuit

NCP4306

100 nF 1 μFDecouplingCapacitors

VL_LAYOUT VL_DRAIN VRDS_ON VL_SOURCE VL_LAYOUT

ISECVDS

LLAYOUTLSOURCERDS_ONLDRAIN


NCP4306

DecouplingCapacitors

LLAYOUT

To VCC

VL_LAYOUTVL_DRAIN VRDS_ON VL_SOURCE VL_LAYOUT

ISEC

VDS

LLAYOUTLSOURCERDS_ONLDRAIN


NCP4306

DecouplingCapacitors

LLAYOUT

1 μF100 nF

a)

b)


NCP4306

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Figure 50. Waveforms from SR System Implemented in a) LLC and b) Flyback Application and Using MOSFET inTO220 Package With Long Leads – SR MOSFET channel Conduction Time is Reduced

a) b)

Note that the efficiency impact caused by the error voltagedue to the parasitic inductance increases with lowerMOSFETs RDS_ON and / or higher operating frequency.

It is thus beneficial to minimize SR MOSFET packageleads length in order to maximize application efficiency. Theoptimum solution for applications with high secondary

current Δi / Δt and high operating frequency is to uselead−less SR MOSFET i.e. SR MOSFET in SMT package.The parasitic inductance of a SMT package is negligiblecausing insignificant CS turn−off threshold shift and thusminimum impact to efficiency (refer to Figure 51).

Figure 51. Waveforms from SR System Implemented in a) LLC b) Flyback Application and Using MOSFET in SMTPackage with Minimized Parasitic Inductance – SR MOSFET Channel Conduction Time is Optimized

a) b)


NCP4306

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It can be deduced from the above paragraphs on theinduced error voltage and parameter tables that turn−offthreshold precision is quite critical. If we consider a SRMOSFET with RDS_ON of 1 mΩ, the 1 mV error voltage onthe CS pin results in a 1 A turn−off current thresholddifference; thus the PCB layout is very critical whenimplementing the SR system. Note that the CS turn−offcomparator is referred to the GND pin. Any parasiticimpedance (resistive or inductive – even on the magnitudeof mΩ and nH values) can cause a high error voltage that isthen evaluated by the CS comparator. Ideally the CSturn–off comparator should detect voltage that is caused bysecondary current directly on the SR MOSFET channel

resistance. In reality there will be small parasitic impedanceon the CS path due to the bonding wires, leads and soldering.To assure the best efficiency results, a Kelvin connection ofthe SR controller to the power circuitry should beimplemented. The GND pin should be connected to the SRMOSFET source soldering point and current sense pinshould be connected to the SR MOSFET drain solderingpoint − refer to Figure 49. Using a Kelvin connection willavoid any impact of PCB layout parasitic elements on the SRcontroller functionality; SR MOSFET parasitic elementswill still play a role in attaining an error voltage. Figure 52and Figure 53 show examples of SR system layouts usingMOSFETs in D2PAK and SO8FL packages.

Figure 52. Recommended Layout When Using SRMOSFET in D2PAK Package

Figure 53. Recommended Layout When Using SRMOSFET in SMT Package SO8 FL

Trigger / Disable inputThe NCP4306 features an ultrafast trigger input that

exhibits a maximum of tPD_TRIG delay from its activation tothe start of SR MOSFET turn−off of process. This input canbe used in applications operated in deep ContinuesConduction Mode (CCM) to further increase efficiency and/ or to activate disable mode of the SR driver in which theconsumption of the NCP4306 is reduced to maximum ofICC_DIS.

NCP4306 is capable to turn−off the SR MOSFET reliablyin CCM applications just based on CS pin information only,without using the trigger input. However, natural delay ofthe ZCD comparator and DRV turn−off delay increaseoverlap between primary and secondary MOSFETsswitching (also known as cross conduction). If one wants toachieve absolutely maximum efficiency with deep CCMapplications, then the trigger signal coming from theprimary side should be applied to the trigger pin. It is goodto set trigger pulse in way there is just short overlap betweenprimary and secondary switches. Short overlap is usually

advantageous than leaving end of conduction phase on bodydiode. Reason is body diode has usually longer recoverytime and resulting overlap time (simultaneously conductionprimary and secondary side switches) is longer. There areseveral possibilities for transferring the trigger signal fromthe primary to the secondary side – refer to Figure 68 andFigure 69.

The trigger signal is blanked for tTRIG_BLANK after theDRV turn−on process has begun. The blanking technique isused to increase trigger input noise immunity against theparasitic ringing that is present during the turn on processdue to the SMPS layout. The trigger input is supersedes theCS input except trigger blanking period. TRIG / DIS signalturns the SR MOSFET off or prohibits its turn−on when theTRIG / DIS pin is pulled above VTRIG_TH.

The SR controller enters disable mode when the triggerpin is pulled−up for more than tDIS_TIM. In disable mode theIC consumption is significantly reduced. To recover fromdisable mode and enter normal operation, the TRIG / DISpin has to be pulled low at least for tDIS_END.


NCP4306

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VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

t1 t2 t3 t4 t5 t6 t7 t8 t9t

Figure 54. Trigger Input Functionality Waveforms Using the Trigger to Turn−off and Block the DRV Signal

Figure 54 shows basic TRIG / DIS input functionality. Att1 the TRIG / DIS pin is pulled low to enter into normaloperation. At t2 the CS pin is dropped below theVTH_CS_ON, signaling to the NCP4306 to start to turn the SRMOSFET on. At t3 the NCP4306 begins to drive theMOSFET. At t4, the SR MOSFET is conducting and theTRIG / DIS pin is pulled high. This high signal on the TRIG

/ DIS pin almost immediately turns off the drive to the SRMOSFET, turning off the MOSFET. The DRV is notturned−on in other case (t6) because the trigger pin is highin the time when CS pin signal crosses turn−on threshold.This figure clearly shows that the DRV can be asserted onlyon falling edge of the CS pin signal in case the trigger inputis at low level (t2).

Figure 55. Trigger Input Functionality Waveforms – Trigger Blanking

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

t1 t2 t3t

TRIG / DIS blank

Min ON−time

tTRIGBLANK

In Figure 55 above, at time t1 the CS pin falls below theVTH_CS_ON while the Trigger is low setting in motion theDRV signal that appears at t2. At time t2 the DRV signal andTrigger blanking clock begin. TRIG / DIS signal goes high

shortly after time t2. Due to the Trigger blanking clock(tTRIG_BLANK) the Trigger’s high signal does not affect theDRV signal until the tTRIG_BLANK timer has expired. Attime t3 the TRIG / DIS signal is reevaluated and the DRV


NCP4306

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signal is turned off. The TRIG / DIS input is blanked fortTRIG_BLANK after DRV set signal to avoid undesirablebehavior during SR MOSFET turn−on event. The blankingtime in combination with high threshold voltage(VTRIG_TH) prevent triggering on ringing and spikes that arepresent on the TRIG / DIS input pin during the SR MOSFET

turn−on process. Controller’s response to the narrow pulseon the TRIG / DIS pin is depicted in Figure 55 – this shorttrigger pulse enables to turn the DRV on for tTRIG_BLANK.Note that this case is valid only if device not entered disablemode before.

Figure 56. Trigger Input Functionality Waveforms – Trigger Blanking Acts Like a Filter

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

TRIG / DIS blank

MIN ON−TIME

VTRIG_BLANK

t1 t2 t3 t4 t5 t6t0 t

Figure 56 above shows almost the same situation as inFigure 55 with one main exception; the TRIG / DIS signalwas not high after trigger blanking timer expired so the DRVsignal remains high. The advantage of the trigger blankingtime during DRV turn−on is evident from Figure 56 since it

acts like a filter on the TRIG / DIS pin. Rising edge of theDRV signal may cause spikes on the trigger input. If it wasn’tfor the TRIG / DIS blanking these spikes, in combinationwith ultra−fast performance of the trigger logic, could turnthe SR MOSFET off in an inappropriate time.

Figure 57. Trigger Input Functionality Waveforms – Trigger over Ride, CS Turn Off and Min On−time

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min ON−time

t1 t2t3 t4 t5 t6t0 tt7 t8


NCP4306

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Figure 57 depicts all possible driver turn−off events indetails when correct VCC is applied. Controller driver isdisabled based on TRIG / DIS input signal in time t2; theTRIG / DIS input overrides the minimum on−time period.

Driver is turned−off according to the CS (VDS) signal (t5marker) and when minimum on−time period elapsedalready. TRIG / DIS signal needs to be low during this event.

If the CS (VDS) voltage reaches VTH_CS_OFF thresholdbefore minimum on−time period ends (t7) and the TRIG /DIS pin is low the DRV is turned−off on the falling edge ofthe minimum on−time period (t8 time marker in Figure 57).This demonstrates the fact that the Trigger over rides theminimum on−time. Minimum on−time has higher prioritythan the CS signal.

In Figure 58 the TRIG / DIS input is low the whole timeand the DRV pulses are purely a function of the CS signaland the minimum on−time. The first DRV pulse terminatedbased on the CS signal and another two DRV pulses areprolonged till the minimum on−time period end despite theCS signal crosses the VTH_CS_OFF threshold earlier.

If a minimum on−time is too long the situation that occursafter time marker t6 Figure 58 can occur, is not correct andshould be avoided. The minimum tON period should beselected shorter to overcome situation that the SR MOSFETis turned−on for too long time. The secondary current thenchanges direction and energy flows back to the transformerthat result in reduced application efficiency and also inexcessive ringing on the primary and secondary MOSFETs.

Figure 58. Minimum On−Time Priority

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min ON−time

t1 t2 t3 t4 t5 t6t0 tt7 t8 t9

Figure 59 shows IC behavior in case the trigger signalfeatures two pulses during one cycle of the VDS (CS) signal.The TRIG / DIS goes low enables the DRV just before timet1 and DRV turns−on because the VDS voltage drops underVTH_CS_ON threshold voltage. The TRIG / DIS signaldisables driver at time t2. The TRIG / DIS drops down toLOW level in time t3, but IC waits for complete minimumoff−time. Minimum off−time execution is blocked until CS

pin voltage goes above VTH_CS_RESET threshold. Next cyclestarts in time t6. The TRIG / DIS goes low and enables theDRV before VDS drops below VTH_CS_ON threshold voltagethus the DRV turns−on in time t6. The TRIG / DIS signalrises up to HIGH level at time t7, consequently DRVturns−off and IC waits for high CS voltage to start minimumoff−time execution.


NCP4306

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Figure 59. TRIG / DIS Input Functionality Waveforms – Two Pulses at One Cycle

VDS = VCS

VTH_CS_RESET

VTH_CS_OFF

VTH_CS_ON

VTRIG/DIS

VDRV

Min OFF−time

Min ON−time

t1 t2 t3 t4 t5 t6t0t

t7 t8 t9 t10

Figure 60. Trigger Input Functionality Waveforms – Disable Mode Activation

Powerconsumption

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min ON−time

t1 t2 t3 t4t0t

tDIS_TIM

In Figure 60 above, at t2 the CS pin rises to VTH_CS_OFFand the SR MOSFET is turned−off. At t3 the TRIG / DISsignal is held high for more than tDIS_TIM. NCP4306 entersdisable mode after tDIS_TIM. Driver output is disabled indisable mode. The DRV stays low (disabled) during

transition to disable mode. Figure 61 shows disable modetransition 2nd case – i.e. when trigger rising edge comesduring the trigger blank period. Figure 62 shows enteringinto disable mode and back to normal sequences.


NCP4306

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Figure 61. Trigger Input Functionality Waveforms – Disable Mode Clock Initiation

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min ON−time

t1 t2 t3t0 t

Powerconsumption

tTRIGBLANK

tDIS_TIM

Figure 62. Trigger Input Functionality Waveforms – Disable and Normal Modes

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min OFF−time

t1 t2 t3t0t

Powerconsumption

tDIS_TIM

tDIS_REC

Disable Mode

t4


NCP4306

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Figure 63 and Figure 64 shows exit from disable mode indetail. NCP4306 requires time up to tDIS_REC to recover allinternal circuitry to normal operation mode whenrecovering from disable mode. The driver is then enabledafter complete tMIN_TOFF period when CS (VDS) voltage isover VTH_CS_RESET threshold. Driver turns−on in the next

cycle on CS (VDS) falling edge signal only (t5 − Figure 63).The DRV stays low during recovery time period. TRIG / DISinput has to be low at least for tDIS_END time to end disablemode and start with recovery. Trigger can go back high aftertDIS_END without recovery interruption.

Figure 63. Trigger Input Functionality Waveforms – Exit from Disable Mode before the Falling Edge of the CS Signal

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min ON−time

t1 t2 t3t0

t

Powerconsumption

t4 t5 t6 t7 t8

Dis

able

Mod

e

Normal Modetime

Rec Waits forcompletetMIN_TOFF

Note: Rec Time = Recovery Time


NCP4306

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Figure 64. Trigger Input Functionality Waveforms

Disable Mode Normal Modetime

Rec Waits forcompletetMIN_TOFF

tDIS_END

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min OFF−time

t1 t2t0

Powerconsumption

t3 t5t4t

Note: Rec Time = Recovery Time


Disable ModeNormal ModeRecovery

tMIN_TOFF

VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min OFF−time

t1 t2t0t

Powerconsumption

t3 t5t4t

t DIS

_RE

C

t6 t7 t8

Waits forcompletetMIN_TOFF


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Figure 65 shows detail IC behavior after disable mode isended. The trigger pin voltage goes low at t1 and aftertDIS_REC IC leaves disable mode (t2). Time interval betweent2 and t3 is too short for complete minimum off−time so

normal mode doesn’t start. VDS voltage goes high again attime t4 and this event starts new minimum off−time timerexecution. Next VDS falling edge below VTH_CS_ON levelactivates driver.


VDS = VCS

VTH_CS_ON

VTRIG / DIS

VDRV

VTH_CS_OFF

VTH_CS_RESET

Min OFF−time

t1 t2t0

Powerconsumption

t3 t5t4t

t6 t7 t8

Dis

able

Mod

e

Normal ModeRecovery

Waits forcompletetMIN_TOFF

tMIN_TOFF

tDIS_REC

Different situation of leaving from disable mode is shownat Figure 66. Minimum off−time execution starts at time t2,but before time elapses VDS voltage falls to negativevoltage. This interrupts minimum off−time execution and

the IC waits to another time when VDS voltage is positiveand then is again started the minimum off−time timer. TheIC returns into normal mode after whole minimum off−timeelapses.

Figure 67. NCP4306 Operation after Start−Up Event

VDS = VCS

VTH_CS_ON

VCCON

VCC

VTH_CS_OFF

VTH_CS_RESET

Min ON−timetMIN_TON

VDRV

Min OFF−time

tMIN_TOFFtMIN_TOFFNot CompletetMIN_TOFF −

IC is not activated

CompletetMIN_TOFF − activates IC

tMIN_TOFF − is stopped due toVDS drops belowVTH_CS_RESET

t1

t

t14t3t2 t4

t5 t7t6 t8

t9 t10 t11 t13t12


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Start−up event waveforms are shown at Figure 67. Astart−up event is very similar to an exit from disable modeevent. The IC waits for a complete minimum off−time event(CS pin voltage is higher than VTH_CS_RESET) until drivepulses can continue. Figure 67 shows how the minimumoff−time timer is reset when CS voltage is oscillatingthrough VTH_CS_RESET level. The NCP4306 startsoperation at time t1 (time t1 can be seen as a wake−up eventfrom the disable mode through TRIG / DIS or LLD pin).Internal logic waits for one complete minimum off−timeperiod to expire before the NCP4306 can activate the driverafter a start−up or wake−up event. The minimum off−timetimer starts to run at time t1, because VCS is higher than

VTH_CS_RESET. The timer is then reset, before its setminimum off−time period expires, at time t2 thanks to CSvoltage lower than VTH_CS_RESET threshold. Theaforementioned reset situation can be seen again at time t3,t4, t5 and t6. A complete minimum off−time period elapsesbetween times t7 and t8 allowing the IC to activate a driveroutput after time t8.

Optional primary triggering techniques for CCM flybackapplication are shown in Figure 68 and Figure 69. NCP4306can operate properly without triggering in CCM, but use oftriggering can reduce the commutation losses and the SRMOSFET drain voltage spike, which results in improvedefficiency in CCM.

Figure 68. Optional Primary Triggering in Deep CCM Application Using Auxiliary Winding

VBULK

VCC

C1 R3

D2

C3

TR1

D3

C2D1

DRV

CSFB

R2

R1

M1

M2

R4C6

C4

D4

GND

R5R6R7

OK1 C5

D5 R7

NCP4306

+ VOUT


The application shown in Figure 68 is simplest and themost cost effective solution for primary SR triggering. Thismethod uses auxiliary winding made of triple insulated wireplaced close to the primary winding section. This auxiliarywinding provides information about primary turn−on eventto the SR controller before the secondary winding reverses.

This is possible thanks to the leakage between primary andsecondary windings that creates natural delay in energytransfer. This technique provides approximately 0.5%efficiency improvement when the application is operated indeep CCM and a transformer that has a leakage of 1% ofprimary inductance is used.


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Figure 69. Optional Primary Triggering in Deep CCM Application Using Trigger Transformer

VBULK

VCC

C1R2

D2

C4

TR1

D3

C3D1

DRV

CSFB

R3

R1

M1

M2

R4

C7

C6

D4

GND

R5R6R7

OK1

C5

D5 R8

NCP4306

+ VOUT


TR2

Application from Figure 69 uses an ultra−small triggertransformer to transfer primary turn−on information directlyfrom the primary controller driver pin to the SR controllertrigger input. Because the trigger input is rising edgesensitive, it is not necessary to transmit the entire primarydriver pulse to the secondary. The coupling capacitor C5 isused to allow the trigger transformer’s core to reset and alsoto prepare a needle pulse (a pulse with width shorter than100 ns) to be transmitted to the NCP4306 TRIG / DIS input.The advantage of needle trigger pulse usage is that therequired volt−second product of the pulse transformer isvery low and that allows the designer to use very small andcheap magnetic. The trigger transformer can even beprepared on a small toroidal ferrite core with outer diameterof 4 mm and four turns for primary and secondary windings

to assure LPRIMARY = LSECONDARY > 10 μH. Proper safetyinsulation between primary and secondary sides can beeasily assured by using triple insulated wire for one or,better, both windings.

This primary triggering technique providesapproximately 0.5% efficiency improvement when theapplication is operated in deep CCM and transformer withleakage of 1% of primary inductance is used.

It is also possible to use capacitive coupling (useadditional capacitor with safety insulation) between theprimary and secondary to transmit the trigger signal. We donot recommend this technique as the parasitic capacitivecurrents between primary and secondary may affect thetrigger signal and thus overall system functionality.


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Minimum tON and tOFF adjustmentThe NCP4306 offers fixed or an adjustable minimum

on−time and off−time blanking periods (depends on ICversion) that ease the implementation of a synchronousrectification system in any SMPS topology. These timersavoid false triggering on the CS input after the MOSFET isturned on or off.

Fixed versions are defined internally and can’t bemodified later or changed during operation.

The adjustment of minimum tON and tOFF periods aredone based on an internal timing capacitance and externalresistors connected to the GND pin – refer to Figure 70 fora better understanding.

Figure 70. Internal Connection of the MIN_TON Generator (the MIN_TOFF Works in the Same Way)

VDD

VREF

tMIN_TON

I R_M

IN_T

ON

CtIR_MIN_TON

RMIN_TON

MIN_TON

GND

To Internal Logic

NCP4306

DischargeSwitch

Current through the MIN_TON adjust resistor can becalculated as:

IR_MIN_TON �Vref

RMIN_TON (eq. 1)

If the internal current mirror creates the same currentthrough RMIN_TON as used the internal timing capacitor (Ct)charging, then the minimum on−time duration can becalculated using this equation.

tMIN_ON � Vt �Vref

IR_MIN_TON� Ct �

VrefVref

RMIN_TON

� Ct � RMIN_TON (eq. 2)

The internal capacitor size would be too large ifIR_MIN_TON was used. The internal current mirror uses aproportional current, given by the internal current mirrorratio. Note that the internal timing comparator delay affects

the accuracy of equations 7 and 8 when MIN_TON orMIN_TOFF times are selected near to their minimumpossible values. Please refer to Figure 71 and Figure 72 formeasured minimum on and off time charts.

Figure 71. MIN_TON Adjust Characteristic Figure 72. MIN_TOFF Adjust Characteristic

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0 5 10 15 20 25 30 35 40 45 50 0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0 5 10 15 20 25 30 35 40 45 50

t MIN

_TO

N [μ

s]

RMIN_TON [kΩ]

t MIN

_TO

FF [μ

s]

RMIN_TOFF [kΩ]


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The absolute minimum tON duration is internally clampedto 55 ns and minimum tOFF duration to 70 ns in order toprevent any potential issues with the minimum tON and / ortOFF input being shorted to GND.

The NCP4306 features dedicated anti−ringing protectionsystem that is implemented with a minimum tOFF blankgenerator. The minimum off−time one−shoot generator isrestarted in the case when the CS pin voltage crossesVTH_CS_RESET threshold and MIN_TOFF period is active.

The total off−time blanking period is prolonged due to theringing in the application (refer to Figure 47).

Some applications may require adaptive minimum on andoff time blanking periods. It is possible to modulate blankingperiods by using an external NPN transistor – refer to Figure73. The modulation signal can be derived based on the loadcurrent, feedback regulator voltage or other applicationparameter.

Figure 73. Possible Connection for MIN_TON and MIN_TOFF Modulation

VDD

VREFtMIN_TON

I R_M

IN_T

ON

RM

IN_T

ON

_2

MIN_TON modulation InputGND

To Internal Logic

NCP4306

DischargeSwitch

RM

IN_T

ON

IR_MIN_TONMIN_TON

ModulationCurrent

dV / dt Detection – Flyback featureThe NCP4306 includes optional feature for flyback type

converters, which operates with shorter primary on−timethan ringing period after demagnetization phase duringmedium / high loads. These applications are for exampleUSB−PD or Quick Charge adapters. Difficulty with thissituation is that minimum off−time doesn’t elapse before

primary side switch is turned on and off again so SRcontroller doesn’t turn on SR mosfet. Whole secondary sidecurrent flows through body diode that makes power loss.Figure 74 shows situation without dV / dt detection. Herecan be seen that without detection next conduction cyclemay be not taken through activated SR transistor. Reason isnot elapsed minimum off−time blanking interval.


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Figure 74. Situation without dV / dt Detection Feature

VTH_CS_RESETVTH_CS_OFF

VDRV

Min OFF−time

VTH_CS_ON

Min ON−time

Primary on−time is very short (shorter than ringing period) for low VOUT

tMIN_TOFF has to be set tolonger time length of ringing

period tMIN_TOFF

Turn−off delayTurn−on delay

tMIN_TON

tMIN_TOFFt MIN

_TO

FF

Driver is not turned−on becausetMIN_TOFF doesn’t elapse

tMIN_TOFF timer is stopped herebecause of VCS< VTH_CS_RESET

VDS = VCS

ISEC

Figure 75 shows how system with activated dV / dtdetection behaves. Min_toff blanking interval is also resetduring voltage drops at CS pin, but if high negative dV / dtoccurs at CS pin, min_toff interval is shorted and SRcontroller is ready to detect CS voltage lower than

VCS_TH_ON and turn SR transistor on. Negative dV / dt at CSpin after primary switch is turned off is high in compare toslope that comes during ringing after demagnetization.Thanks to this we can safely detect end of primary on−timefrom ringing.

Figure 75. Situation with Enabled dV / dt Detection

VTH_CS_RESET

VTH_CS_OFF

Min OFF−time

VTH_CS_ON

Min ON−time

Turn−on delay Turn−off delay

Negative dV / dtdetector at CS pin

VDRV

tMIN_TOFF

tMIN_TOFFtMIN_TOFF

CS voltage drops belowVTH_CS_ON but at timewhen min tOFF doesn’t

elapse and just low dV / dtis detected so DRV is not

activated

tMIN_TOFF timer is stopped herebecause of VCS< VTH_CS_RESET

tMIN_TOFF timer doesn’telapse but high dV / dt is

detected so DRV is enable

tMIN_TOFF has to be setto longer time than length

of ringing period

VDS = VCS

ISEC

tMIN_TON

Exception Timer – LLC featureException timer is special feature for LLC type SMPS. It

is mainly targeted to operation under light / medium load,where secondary side SMPS current shape is not sine, but itcontains part of capacitive peak optionally with no current

part followed by distorted sine. Examples of current shapeis shown in Figure 76. This figure shows different currentshapes at different loading. Lower loading makes shapemore distorted from ideal sine.


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Figure 76. Current Shapes in LLC Examples

t

ISEC

Problematic shapes may cause prematurely SR transistorturn−off, because CS voltage may get to zero or to positivevoltage (due to low current or high dI / dt and parasiticinductance). Sensed voltage drop can be seen in Figure 77.This situation is valid for SR mosfet with RDSON = 1 mΩ andwith package (SMT) parasitic inductance LPACPAR =0.5 nH. There can be seen that SR transistor should be turnedoff in time between 0.4 to 1.5 μs, because CS voltage is

above VTH_CS_OFF threshold. Turn−off process can bemasked by min_ton blanking interval, but in this case isneeded to set it at least to 1.5 μs that can make issue duringvery light load where current flows just short time and longmin_ton may cause reverse current from output capacitorsback to transformer and may change soft switchingcondition to hard switching at primary side.

-10

-8

-6

-4

-2

2

0

0 1 2 3 4 5 6

V DS[m

V]

7

0,00

0,50

1,00

1,50

2,00

3,00

2,50

0 1 2 3 4 5 6

ISE

C[A

]

7

Drop just atRDSon

Drop at RDSonand parasiticinductance

VTH_CS_OFF

Figure 77. Sensed Voltage Drop at SR Transistor in LLC during Light / Medium Load

t[μs] t[μs]

To early SR transistor turn−off is not issue just fromefficiency point of view, but also from system stability pointof view. When load is decreased, feedback loop asks primaryside for lower power that changes secondary side currentshape and SR driver can be turned off shortly after min_toffelapses. This causes lower efficiency transfer to secondaryside and output voltage starts to decrease. Feedback loop

asks for more power, secondary current shape changes andSR driver starts to conduct whole period again that improvesenergy transfer efficiency and output voltage starts toincrease. This has to be again regulated by feedback loop andeverything starts from begin and make SMPS oscillationsthat can be accompany with audible noise.


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Figure 78. LLC System Oscillation due to Short SR Transistor Conduction

ISEC

VDS1

VDRV1

MIN_TON Bodydiode conducts

VDS2

VDRV2

MIN_TON

Bodydiode conducts

Bodydiode conducts Bodydiode conducts

CS voltage goes above 0 V after

min_ton = SR is turned off

Regulation loop increases transferred power because thanks to low

SR conduction angle lot of power is lose at body diode

Regulation loop decreases transferred power because thanks to SR

it is too much voltage at the output

Operation of new feature is shown in Figure 79. Currentshape makes drop at SR transistor with 1 mΩ and 0.5 nHshown as VDS that is sensed at CS pin and on and offcomparators decide about SR operation based on thisvoltage. Driver is turned on and exception timer is startedwhen VCS drops below VCS_TH_ON. During minimumon−time blanking interval off comparator is not active. CSpin voltage is above VTH_CS_OFF after minimum on−timeelapses so driver is turned−off and because exception timerdoesn’t elapse, min_ton blanking interval is started. Duringthis time on comparator output is blanked. Reason is to avoidquick driver turning on and off that would just increaseconsumption. When min_ton blanking interval elapses CS

voltage is again below VTH_CS_ON and exception timer isnot elapsed, driver can be turned on again simultaneouslywith minimum on−time interval. Driver is turned off againalmost at the end of conduction phase, but this is correct turnoff. Min−ton blanking interval doesn’t start, becauseexception timer elapsed before so SR controller waits forVCS > VCS_TH_RESET to start minimum off time blankingtimer.

Exception timer length is given as multiple of minimumon time interval. It should be not set to longer time than

tEXC �1

3 � fSWMAX (eq. 3)where fSWMAX is maximum LLC switching frequency.


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Figure 79. Exception Timer Operation

Body diode drop(not in scale)

Driver can beturned on again up

to this point

VDS = VCS

VTH_CS_OFF

VTH_CS_ON

Min ON−time

ISEC

VTH_CS_RESET

Min OFF−time

DRV

Min ON−time_2

Exception timer

∼0.25 A

∼2.7 A

Light Load DetectionLight load detection feature is feature which task is to

decrease SR controller consumption during time when SRtransistor switching is not needed. This is usually during noload and light load condition when static SR controllerconsumption starts to play role. Goal is to disable controllerduring no switching time to eliminate static consumptionand turn−on SR transistor as soon as possible whenswitching comes.

Internal simplified block diagram is shown in Figure 80.Main parts of this system are comparator at CS input that

informs about CS voltage lower than zero (body diode or SRtransistor conducting), LLD timer with set able nominaltime and possibility to reduce it to one half and finally D flipflop with Disable signal output. Nominal time can be set byresistor at LLD pin connected to ground or internally duringproduction. Recommended resistor values are shown inTable 6. In case of very noisy system, capacitor in parallelto LLD resistor may be used. Capacitor value impactsstart−up time, because capacitor has to be charged abovedisable threshold by internal LLD current source.

Figure 80. LLD Internal Block Diagram

VCSLLD

CSRESET ELAPSED

LLDTimer

Set maxto tLLD

Set maxto tLLD / 2

tim > 1/4 tLLD

S

RQ

Disable


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Table 6. PIN FUNCTION DESCRIPTION

LLD setting tLLD [�s] IC disabled 70 130 280 540 1075 LLD disabled

RLLD [k�] 470*

*floating pin allowed, small cap for noise robustness improvement recommended

Logic function is also described by bubble diagram inFigure 81. LLD timer is running every time when CS pinvoltage is positive (body diode and or transistor notconducting). If conduction doesn’t come sooner than LLDtimer elapses, DISABLE flag is set (IC is sent into lowconsumption mode), LLD timer length is changed to tLLD /2 (this adds some hysteresis in system and helps keepingoverall system stable) and timer is also reset. SR controllerwaits for falling edge at CS pin (begin of new conductioncycle). When CS goes negative, disable mode is deactivated

and IC starts to wake up (takes tLLD_DIS_REC, system wakeup is controlled same as exit from disable mode by TRIG /DIS pin). End of conduction phase (CS voltage goespositive) starts LLD timer. If next conduction phase comesshortly after first (pulses in skip burst) so shortly than tLLD/ 4 just LLD timer is reset. LLD timer length is set back totLLD only when new conduction phase comes after previousin time between tLLD / 4 to tLLD / 2. This situation happenswhen load is slowly increased and skip bursts come moreoften.

Figure 81. LLD Operation Bubble Diagram

Reset TIMDISABLE = 0

LLD_CMP &TIM CNT < tLLD

LLD_CMP

Start

Reset TIMDISABLE = 0

tTIM = tLLD

DISABLE = 1tTIM = 1/2 tLLD

Reset TIM

LLD TIM isRUNNING

1/4

Example of LLD operation with flyback convertor can beseen in Figure 82. SMPS works under heavy load from point0 to 1 where switching pulses comes regularly at highfrequency that resets LLD timer soon after begin ofcounting. Load is significantly decreased to light load atpoint 1 so primary controller turns to skip mode. LLD timerelapses during skip so controller enters disable mode withvery low consumption and change LLD timer maximum totLLD / 2. Switching pulse in skip comes at time 3, this resetsLLD timer and starts IC wake−up. Controller is waked upfully before point 4 and turns−on SR transistor. There isagain no switching from 4 to 6 and thanks to it, LLD timerelapses at point 5 and controller enters disable mode again.Disable mode is ended at time 6, because new cycle comes.SR controller wakes−up and next pulse in skip burst isconducted via SR transistor. Time between 7 and 8 is delaybetween skip burst. Time is still less than tLLD / 4, LLD timer

interval is not changed. Pulse at time 8 is fully conducted viaSR transistor, because controller was not in disable modebefore pulse came. No switching period between 9 and 11 islonger than tLLD / 2 that changes LLD timer setting to tLLD.This is because shorter delay between skip burst meanshigher load. Pulses are transferred via SR transistor at time11 and 12, because disable mode was not activated. Load isbeing decreased again between time 12 to 15 so at time 15SR controller enters disable mode and LLD timer time isreduced again to tLLD / 2. Second pulse in skip burst is againtransferred via turned on SR transistor. Disable mode isactivated after tLLD / 2 at time 18. Load is sharply changedat time 19 that means LLD timer is reset each pulse andtimers time is kept at tLLD / 2. Load is removed at time 20 anddisable is activated at time 21. Suitable LLD timer setting forflyback type of SMPS is 540 or 1075 μs (for special type280 μs).


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Figure 82. LLD Operation with Flyback SMPS

VDS = VCS

DRV

DIS

ICC

LLD timtLLD

t1 t2 t4 t1 t2

t1t2

t4

0 1 42 3 5 6 7 8 9 101112 13 14 15 16 17 18 19 20 21 22

t2

Example of LLD operation with LLC convertor can beseen in Figure 83. SMPS works under heavy load from point0 to 3. Both LLD timers are reset each cycle before LLDtimer reaches tLLD / 4 and disable mode is not activated.SMPS load decreases at point 3 and goes into skip. LLDtimers elapse during no switching time and change LLDtimer time to tLLD / 2. When skip burst comes at time 6channel 2 starts to wake up, channel 1 starts to wake up attime 7. Both channels are ready to conduct via SR transistor

at time 8 respectively 9. Skip burst ends at time 12, LLDtimers elapse at time 13 and 14 (reached tLLD / 2) and SRcontrollers enter disable mode. Controllers wake up at time15 and 16 same as was in time 6 and 7. SMPS goes into skipin time 21, but load is connected soon and SMPS starts tooperate under higher load from time 22. LLD timers reachtime higher than tLLD / 4 but lower than tLLD / 2 so LLDtimers maximum is set to tLLD. LLD timer setting for LLCmay be set to lower times.

Figure 83. LLD Operation with LLC SMPS

VDS1 = VCS1

DRV1

LLD tim1

0 1 42 3 5 6 7 8 9 10 11 12 13 14 15 16 17 19 20 21 22

VDS2 = VCS2

DRV2

DIS1DIS2

LLD tim2tLLD1

tLLD1

23 24 25 26 27 28

t1

t2

t4


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Operation flowFollowed bubble diagram at Figure 84 shows overall

operation flow. Black bubbles are fundamental parts ofsystem. States for dV / dt feature are colored by blue colorand states for LLC feature (exception timer) are in red. LLC

and dV / dt features are never activated both at same time.Operation starts in bubble start where system comes whenVCC is higher than UVLO level and / or disable mode isactivated (by LLD or TRIG / DIS pin).

Figure 84. Overall Operation Bubble Diagram

Power dissipation calculationIt is important to consider the power dissipation in the

MOSFET driver of a SR system. If no external gate resistoris used and the internal gate resistance of the MOSFET isvery low, nearly all energy losses related to gate charge aredissipated in the driver. Thus it is necessary to check the SRdriver power losses in the target application to avoid overtemperature and to optimize efficiency.

In SR systems the body diode of the SR MOSFET startsconducting before SR MOSFET is turned−on, because thereis some delay from VTH_CS_ON detect to turn−on the driver.On the other hand, the SR MOSFET turn off process alwaysstarts before the drain to source voltage rises up

significantly. Therefore, the MOSFET switch alwaysoperates under Zero Voltage Switching (ZVS) conditionswhen in a synchronous rectification system.

The following steps show how to approximately calculatethe power dissipation and DIE temperature of the NCP4306controller. Note that real results can vary due to the effectsof the PCB layout on the thermal resistance.

Step 1 – MOSFET gate to source capacitance:During ZVS operation the gate to drain capacitance does

not have a Miller effect like in hard switching systemsbecause the drain to source voltage does not change (or itschange is negligible).

Figure 85. Typical MOSFET Capacitances Dependency on VDS and VGS Voltages


NCP4306

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Ciss � Cgs � Cgd (eq. 4)

Crss � Cgd (eq. 5)

Coss � Cds � Cgd (eq. 6)

Therefore, the input capacitance of a MOSFET operatingin ZVS mode is given by the parallel combination of the gateto source and gate to drain capacitances (i.e. Ciss capacitancefor given gate to source voltage). The total gate charge,Qg_total, of most MOSFETs on the market is defined for hardswitching conditions. In order to accurately calculate thedriving losses in a SR system, it is necessary to determine thegate charge of the MOSFET for operation specifically in aZVS system. Some manufacturers define this parameter asQg_ZVS. Unfortunately, most datasheets do not provide thisdata. If the Ciss (or Qg_ZVS) parameter is not available thenit will need to be measured. Please note that the inputcapacitance is not linear (as shown Figure 85) and it needsto be characterized for a given gate voltage clamp level.

Step 2 – Gate drive losses calculation:Gate drive losses are affected by the gate driver clamp

voltage. Gate driver clamp voltage selection depends on thetype of MOSFET used (threshold voltage versus channelresistance). The total power losses (driving loses andconduction losses) should be considered when selecting thegate driver clamp voltage. Most of today’s MOSFETs for SRsystems feature low RDS_ON for 5 V VGS voltage. The

NCP4306 offers both a 5 V gate clamp and a 10 V gateclamp for those MOSFET that require higher gate to sourcevoltage.

The total driving loss can be calculated using the selectedgate driver clamp voltage and the input capacitance of theMOSFET:

PDRV_total � VCC � VCLAMP � CG_ZVS � fSW (eq. 7)

Where:VCC is the NCP4306 supply voltageVCLAMP is the driver clamp voltageCg_ZVS is the gate to source capacitance of theMOSFET in ZVS modefsw is the switching frequency of the target application

The total driving power loss won’t only be dissipated inthe IC, but also in external resistances like the external gateresistor (if used) and the MOSFET internal gate resistance(Figure 86). Because NCP4306 features a clamped driver,it’s high side portion can be modeled as a regular driverswitch with equivalent resistance and a series voltagesource. The low side driver switch resistance does not dropimmediately at turn−off, thus it is necessary to use anequivalent value (RDRV_SIN_EQK) for calculations. Thismethod simplifies power losses calculations and stillprovides acceptable accuracy. Internal driver powerdissipation can then be calculated using equation 10:

Figure 86. Equivalent Schematic of Gate Drive Circuitry

VCC

VCC − VCLAMP−

+

DRV

GNDRDRV_SINK_EQ

RDRV_SOURCE_EQRG_EXT

SR MOSFET

RG_INT

CG_ZVS


NCP4306

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PDRV_IC �12� Cg_ZVS � VCLAMP2 � fSW �� RDRV_SINK_EQRDRV_SINK_EQ � RG_EXT � Rg_int�� Cg_ZVS � VCLAMP � fSW � (VCC � VCLAMP) (eq. 8)

� � 12� Cg_ZVS � VCLAMP2 � fSW �� RDRV_SOURCE_EQRDRV_SOURCE_EQ � RG_EXT � Rg_int� (eq. 9)

Where:RDRV_SINK_EQ is the NCP4306 driver low side switchequivalent resistance (1.6 Ω)RDRV_SOURCE_EQ is the NCP4306 driver high sideswitch equivalent resistance (7 Ω)RG_EXT is the external gate resistor (if used)Rg_int is the internal gate resistance of the MOSFET

Step 3 – IC consumption calculation:In this step, power dissipation related to the internal IC

consumption is calculated. This power loss is given by theICC current and the IC supply voltage. The ICC currentdepends on switching frequency and also on the selected mintON and tOFF periods because there is current flowing outfrom the MIN_TON and MIN_TOFF pins. The mostaccurate method for calculating these losses is to measurethe ICC current when CLOAD = 0 nF and the IC is switchingat the target frequency with given min_tON and min_tOFFadjust resistors. IC consumption losses can be calculated as:

PCC � VCC � ICC (eq. 10)

Step 4 – IC die temperature arise calculation:The die temperature can be calculated now that the total

internal power losses have been determined (driver lossesplus internal IC consumption losses). The SO8 packagethermal resistance is specified in the maximum ratings tablefor a 35 μm thin copper layer with no extra copper plates onany pin (i.e. just 0.5 mm trace to each pin with standardsoldering points are used).

The die temperature is calculated as:

TDIE � (PDRV_IC � PCC) � R�J�A � TA (eq. 11)

Where:PDRV_IC is the IC driver internal power dissipationPCC is the IC control internal power dissipation R J−A is the thermal resistance from junction to ambientTA is the ambient temperature


NCP4306

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OPN coding tableNCP4306 OPN is built from prefix of NCP4306 and

postfix that consist of seven letters. Meaning of these lettersare shown in table 7.

Table 7. OPN CODING TABLE

NCP4306xxxxxxx

Postfix Index Parameter Postfix Parameter

1 Pinout A MIN_TON, MIN_TOFF, LLD, TRIG / DIS − 8 pins

B MIN_TON, LLD

C MIN_TOFF, LLD

D MIN_TON, MIN_TOFF

E MIN_TOFF, TRIG / DIS

F MIN_TON, TRIG / DIS

G TRIG / DIS, LLD

H None

2 DRV A DRV CLMP = 10 V

B DRV CLMP = 5 V

3 dV / dt + exception A None

D Flyback (dV / dt) − 100 V / μs

H LLC exception − multiplier 4

4 MIN_TON A 130 ns

B 220 ns

C 310 ns

D 400 ns

E 500 ns

F 600 ns

G 800 ns

H 1000 ns

I 1200 ns

J 1400 ns

K 1700 ns

L 2000 ns

Z External

5 MIN_TOFF A 0.9 μs

B 1.0 μs

C 1.1 μs

D 1.2 μs

E 1.4 μs

F 1.6 μs

G 1.8 μs

H 2.0 μs

I 2.2 μs

J 2.4 μs

K 2.6 μs

L 2.9 μs

M 3.2 μs

N 3.5 μs

O 3.9 μs

Z External


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Table 7. OPN CODING TABLE (continued)

NCP4306xxxxxxx

Postfix Index ParameterPostfixParameter

6 LLD A 68 μs

B 130 μs

C 280 μs

D 540 μs

E 1075 μs

F Disabled

Z External

7 Reserved A −


NCP4306

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PACKAGE DIMENSIONS

SOIC−8 NBCASE 751−07

ISSUE AK

SEATINGPLANE

14

58

N

J

X 45�

K

NOTES:1. DIMENSIONING AND TOLERANCING PER

ANSI Y14.5M, 1982.2. CONTROLLING DIMENSION: MILLIMETER.3. DIMENSION A AND B DO NOT INCLUDE

MOLD PROTRUSION.4. MAXIMUM MOLD PROTRUSION 0.15 (0.006)

PER SIDE.5. DIMENSION D DOES NOT INCLUDE DAMBAR

PROTRUSION. ALLOWABLE DAMBARPROTRUSION SHALL BE 0.127 (0.005) TOTALIN EXCESS OF THE D DIMENSION ATMAXIMUM MATERIAL CONDITION.

6. 751−01 THRU 751−06 ARE OBSOLETE. NEWSTANDARD IS 751−07.

A

B S

DH

C

0.10 (0.004)

DIMA

MIN MAX MIN MAXINCHES

4.80 5.00 0.189 0.197

MILLIMETERS

B 3.80 4.00 0.150 0.157C 1.35 1.75 0.053 0.069D 0.33 0.51 0.013 0.020G 1.27 BSC 0.050 BSCH 0.10 0.25 0.004 0.010J 0.19 0.25 0.007 0.010K 0.40 1.27 0.016 0.050M 0 8 0 8 N 0.25 0.50 0.010 0.020S 5.80 6.20 0.228 0.244

−X−

−Y−

G

MYM0.25 (0.010)

−Z−

YM0.25 (0.010) Z S X S

M� � � �

1.520.060

7.00.275

0.60.024

1.2700.050

4.00.155

� mminches

�SCALE 6:1*For additional information on our Pb−Free strategy and soldering

details, please download the ON Semiconductor Soldering andMounting Techniques Reference Manual, SOLDERRM / D.

SOLDERING FOOTPRINT*


NCP4306

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PACKAGE DIMENSIONS

ÉÉÉÉ

TSOP−6CASE 318G−02

ISSUE V

2 3

456

D

1

eb

E1

A1

A0.05

NOTES:1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.2. CONTROLLING DIMENSION: MILLIMETERS.3. MAXIMUM LEAD THICKNESS INCLUDES LEAD FINISH. MINIMUM

LEAD THICKNESS IS THE MINIMUM THICKNESS OF BASE MATERIAL.4. DIMENSIONS D AND E1 DO NOT INCLUDE MOLD FLASH,

PROTRUSIONS, OR GATE BURRS. MOLD FLASH, PROTRUSIONS, ORGATE BURRS SHALL NOT EXCEED 0.15 PER SIDE. DIMENSIONS DAND E1 ARE DETERMINED AT DATUM H.

5. PIN ONE INDICATOR MUST BE LOCATED IN THE INDICATED ZONE.

c

*For additional information on our Pb−Free strategy and solderingdetails, please download the ON Semiconductor Soldering andMounting Techniques Reference Manual, SOLDERRM / D.

SOLDERING FOOTPRINT*

DIMA

MIN NOM MAXMILLIMETERS

0.90 1.00 1.10A1 0.01 0.06 0.10b 0.25 0.38 0.50c 0.10 0.18 0.26D 2.90 3.00 3.10E 2.50 2.75 3.00

e 0.85 0.95 1.05L 0.20 0.40 0.60

0.25 BSCL2−0� 10�

1.30 1.50 1.70E1

E

RECOMMENDED

NOTE 5

LCM

H

L2

SEATINGPLANE

GAUGEPLANE

DETAIL Z

DETAIL Z

0.606X

3.200.956X

0.95PITCH

DIMENSIONS: MILLIMETERS

M


NCP4306

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NCP4306 - Secondary Side Synchronous Rectification Driver ... · NCP4306 6 ABSOLUTE MAXIMUM RATINGS Table 3. ABSOLUTE MAXIMUM RATINGS Rating Symbol Value Unit Supply Voltage VCC −0.3