Page1 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current *

Applications Cellular and Smart Phones (Top View) PDAs MP3 Player DSP Core Supplies Digital Still Cameras Portable instruments

Pin Description

Pin Number Pin Name Pin Function

1 RUN Regulator Enable control input. Drive RUN above 1.5V to turn on the part. Drive RUN below 0.3V to turn it off. In shutdown, all functions are disable drawing ＜1μA supply current. Do not leave RUN floating.

2 GND Ground

3 SW Power Switch Output. It is the Switch node connection to inductor. This pin connects to the drains of the internal P-CH and N-CH MOSFET switches.

4 IN Supply Input Pin. Must be closely decoupled to GND, pin2, with a 2.2μF or greater ceramic capacitor.

5 FB/VOUT

VFB (OCP2158): Feedback Input Pin. Connected FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. VOUT (OCP2158-1.2/1.5/1.8): Output Voltage Feedback Pin. An internal resistive divider divides the output voltage down for comparison to the internal reference voltage.

General Description The OCP2158 is a 1.5MHz constant frequency, high efficiency, slope compensated current mode PWM step-down converter. The devices integrate a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. The OCP2158 can operate from a 2.5V to 6.5V input voltage and is ideal for powering portable equipment that runs from a single cell lithium-ion (Li+) battery. It can supply 700mA output current and can also run at 100% duty cycle for low dropout operation, extending battery life in portable system. The OCP2158 features a Power Saving Mode which reduces quiescent current to just 30μA and significantly improves efficiency at light load. The OCP2158 is offered in a low profile (1mm) 5-pin, SOT package, and is available in an adjustable version and fixed output voltage of 1.2V, 1.5V and 1.8V.

Features High Efficiency : Up to 96% 1.5MHz Constant Switching Frequency 600mA Output Current at VIN=3.0V Integrated Main switch and synchronous rectifier No Schottky Diode Required 2.5V to 6.5V Input Voltage Range Output Voltage as low as 0.6V 100% Duty Cycle in Dropout Low Quiescent Current : 30μA ＜1μA Shutdown Current Slope Compensated Current Mode Control for

Excellent Line and Load Transient Response Short Circuit and Thermal Fault Protection

Space Saving 5-pin Thin SOT23 package

5

4

1

2

3 VIN

VFB

SW

GND

Run

Pin Configuration

Page2 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Block Diagram For Adjustable Output R1+R2 is external.

Thermal Resistance (Note 1)

Package θJA (/W) θJC (/W) TSOT23-5L 250 110

Note 1: Thermal Resistance is specified with approximately 1 square of 1 oz copper.

Absolute Maximum Ratings (Note 2)

Parameter Rating Unit Input Supply Voltage -0.3 to +6.8 V RUN, VFB Voltages -0.3 to VIN V

SW Voltages -0.3 to VIN V Peak SW Sink and Source Current 1.5 A

Operating Temperature Range -40 to +85 Junction Temperature (Note 3) +125 Storage Temperature Range -65 to 150

Lead Temperature ( solding, 10 sec.) +300 Note 2: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 3: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ=TA+PD×θJA

RISENSE

1RUN

SW

+

-

4

PWMRS LATCH

GND

EA

+

-

R1

SHUTDOWN

DRV

REF

Q

0.6V

NO

N_Q

BLANKING

0.6V

OV

ER

LAP

5

IZERO

OVDET

COMP

Vin COMP

COMP

LOGIC

+

-

CO

NTR

OL

R

0.65V

+

- S

2

+

-

SLOPEOSC

R2

COMPVIN

3

Pow erSavingModeCOMP

VFB/VOUT

Page3 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Electrical Characteristics (Note 4) (VIN=VRUN=3.6V, TA=25, Test circuit of Figure 1, Unless otherwise noted)

Parameter Condition Min. Typ. Max. Unit Input Voltage Range 2.5 6.5 V

Input DC Supply Current Active Mode

Power Saving Mode Shutdown Mode

VFB=0.5V

VFB=0.63V VFB=0V, VIN=4.2V

270 35

0.08

400 50 1.0

μA

TA=+25 0.5880 0.6000 0.6120 V TA=0≤TA≤85 0.5865 0.6000 0.6135 V Regulated Feedback Voltage

TA=-40≤TA≤85 0.5850 0.6000 0.6150 V VFB Input Bias Current VFB=0.65V ±30 nA

Reference Voltage Line Regulation VIN=2.5V to 6.5V, VOUT=VFB(R2=0) 0.11 0.40 %/V OCP2158-1.2V: -40≤TA≤85 1.164 1.200 1.236 V OCP2158-1.5V: -40≤TA≤85 1.455 1.500 1.545 V Regulated Output Voltage OCP2158-1.8V: -40≤TA≤85 1.746 1.800 1.854 V

Output Voltage Line Regulation VIN=2.5V to 6.5V, IOUT=10mA 0.11 0.40 %/V Output Voltage Load Regulation IOUT from 0 to 600mA 0.0015 %/mA

Maximum Output Current VIN=3.0V 700 mA Oscillator Frequency VFB=0.6V or VOUT=100% 1.2 1.5 1.8 MHz

RDS(ON) of P-CH MOSFET ISW=300mA 0.30 0.50 Ω RDS(ON) of N-CH MOSFET ISW=-300mA 0.20 0.45 Ω

Peak Inductor Current VIN=3V, VFB=0.5V or VOUT=90%, Duty Cycle＜35% 1.20 A

SW Leakage VRUN=0V, VSW=0V or 5V, VIN=5V ±0.01 ±1 μA RUN Threshold -40≤TA≤85 0.3 0.45 1.30 V

RUN Leakage Current ±0.1 ±1 μA Note 4: 100% production test at +25. Specifications over the temperature range are guaranteed by design and characterization.

Page4 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Typical Performance Characteristics (Test Figure 1 below unless otherwise specified)

Input Voltage (V)

Effi

cien

cy

55%

65%

75%

80%

90%95%

2 3 4 5 6

Efficiency vs Input Voltage

60%

70%

85%

100%

50%

VOUT=1.8V Ta=25

IOUT=100mA

IOUT=500mA IOUT=10mA

2.5 3.5 4.5 5.5Load Current (mA)

Effi

cien

cy45%

60%

70%75%

90%95%

0.1 1 10 100 1000

Efficiency vs Load Current

50%

65%

80%

100%

40%

55%

85%

2.7V

3.6V

4.2V

VOUT=1.2V TA=25

Load Current (mA)

Effi

cien

cy

45%

60%

70%75%

90%95%

0.1 1 10 100 1000

Efficiency vs Load Current

50%

65%

80%

100%

40%

55%

85%

2.7V

3.6V

4.2V

VOUT=1.5V TA=25

Load Current (mA)

Effi

cien

cy

45%

60%

70%75%

90%95%

0.1 1 10 100 1000

Efficiency vs Load Current

50%

65%

80%

100%

40%

55%

85%

2.7V

3.6V

4.2V VOUT=1.8V

TA=25

Page5 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Typical Performance Characteristics (Continued)

Load Current (mA)

Effi

cien

cy

45%

60%

70%75%

90%95%

0.1 1 10 100 1000

Efficiency vs Load Current

50%

65%

80%

100%

40%

55%

85%

2.7V

3.6V

4.2V

VOUT=2.5V TA=25

0 200 400 600 800 10001.641.66

1.72

1.761.78

1.8

Load Current (mA)

Out

put V

olta

ge (V

)

Output Voltage vs Load Current

1.7

1.84

1200

1.68

1.74

1.82

Vin=3.6V Vout=1.8V

L=2.2µH

Input Voltage (V)

Freq

uenc

y (M

Hz)

1.37

1.39

1.41

1.42

1.441.45

2 3.6 4.5 5.4

Frequency vs Input Voltage

1.38

1.40

1.43

1.46

1.363.15 4.05 4.95

VOUT=1.8V ILOAD=150mA

L=2.2µH 1.5 3.5 4.5 5 6.50.10

0.30

0.45

0.50

Input Voltage (V)

RD

S(O

N) (Ω)

RDS(ON) vs Input Voltage

0.25

2.5 3 6

0.15

0.20

0.35

0.40

2 4 5.5

Main Switch

Synchronous Switch

Page6 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Typical Performance Characteristics (Continued)

-50 -30 -10 10 30 700.60080.6016

0.6040

0.60560.6064

0.6072

Ref

eren

ce V

olta

ge (V

)

Reference Voltage vs Temperature

0.6032

90

0.6024

0.6048

0.6080

50Temperature ()

VIN=3.6V

-45 15 30 45 900.18

0.22

0.28

0.32

0.36

0.38

Temperature ()

RDS(ON) vs Temperature

0.26

-30 -15 75

0.20

0.24

0.30

0.34

0 60

RD

S(O

N) (Ω

) N_RDS(ON)

P_RDS(ON)

VIN=3.6V

2.7 3.9 4.2 4.5 5.40.26

0.28

0.29

0.31

0.32

0.32

Input Voltage (V)

Input Current vs Input Voltage

0.29

3 3.3 5.1

0.27

0.28

0.30

0.31

3.6 4.8

Inpu

t Cur

rent

(mA

)

5.7

VOUT=1.8VILOAD=0

L=2.2µH

-50 25 50 1001.10

1.20

1.35

1.45

1.55

1.60

Temperature ()

Frequency vs Temperature

1.30

-25 75

1.15

1.25

1.40

1.50

0

OS

C F

requ

ency

(MH

z)

VIN=3.6V

-50 10 30 90200

220

260

280

320

Temperature ()

Supply Current vs Temperature

-30 50

240

300

-10

Supp

ly C

urre

nt (µ

A)

70

Page7 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Typical Performance Characteristics (Continued)

Load Transient Response Power Saving Mode to PWM Mode

Iload=26mA to 400mA, L=2.2μH, Cin=10μF, Cout=10μF, Vin=3.6V, Vout=1.8V

Load Transient Response PWM Mode Only

Iload=180mA to 400mA, L=2.2μH, Cin=10μF, Cout=10μF, Vin=3.6V, Vout=1.8V

Page8 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Operation OCP2158 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC Converter suppliers 700mA output current at VIN=3V with input voltage range from 2.5V to 6.5V.

Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for excellent load and line responses and protection of the internal main switch (P-Ch MOSFET) and synchronous rectifier(N-Ch MOSFET). During normal operation, the internal P-Ch MOSFET is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. The current comparator, ICOMP, limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the faults is no longer present.

Power Saving Operation At very light loads, the OCP2158 automatically enters Power Saving Mode. In power saving mode at light load, a control circuit puts most of the circuit into sleep in order to reduce quiescent current and improve efficiency at light load. When the output voltage drops to certain threshold, the control circuit turns back on the oscillator and the PWM control loop, boosting output backup. When an upper threshold is reached, the control circuit again puts most of circuit into sleep, reducing quiescent current. While the power saving mode improves light load efficiency, however, with the turning on and off, the noise or ripple voltage is larger than that in the PWM Mode.

Dropout Operation When the input voltage decreases toward the value of the output voltage, the OCP2158 allows the main switch to remain on for more than one switching cycle and increases the duty cycle until it reaches 100%. The duty cycle D of a step-down converter is defined as:

OUTON OSC

IN

VD=T f 100% 100%V

× × ≈ ×

Where TON is the main switch on time and fOSC is the oscillator frequency. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage, the RDS(ON) of the P-Channel MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the IC.

Maximum Load Current The OCP2158 will operate with input supply voltages as low as 2.5V, however, the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases.

Page9 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Application Information Setting the Output Voltage Figure 1 above shows the basic application circuit with OCP2158 adjustable output version. The external resistor sets the output voltage according to the following equation:

OUTR2V 0.6V 1+R1

⎛ ⎞= ⎜ ⎟⎝ ⎠

R1=316kΩ for all outputs; R2=316kΩ for VOUT=1.2V, R2=470kΩ for VOUT=1.5V, R2=634kΩ for VOUT=1.8V and R2=1000kΩ for VOUT=2.5V. Inductor Selection For most designs, the OCP2158 operates with inductors of 1μH to 4.7μH. Low inductance values are physically smaller but require faster switching, which results in some efficiency loss. The inductor value can be derived from the following equation:

( )OUT IN OUT

IN L OSC

V V VL

V I f× −

=×Δ ×

Where ΔIL is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple currents. Choose inductor ripple current approximately 35% of the maximum load current 700mA, or ΔIL=245mA. For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended inductor is 2.2μH. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (700mA+105mA). Table 1 lists some typical surface mount inductors that meet target applications for the OCP2158.

Run

C14.7μF

L1

VIN 2.5V~6.5V

2.2μH

Vin

GND

OCP2158

C210μF

L12.2uH

VFB

1

VOUT1.8V

VOUT 1.8V

C322PF

4

Fig.2 Basic Application Circuit with fixed output versions

C210μF

SW

R1316K

5

C14.7μF

OCP2158

GND

1

2

Fig.1 Basic Application Circuit with OCP2158 adjustable version

VIN 2.5V~6.5V

3

R2634K

Vout

2

4

3

Run

5

SW

Vin

Page10 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Part # L (μH) Max DCR (mΩ) Rated D.C. Current (A) Size W×L×H (mm) Sumida CR43

1.4 2.2 3.3 4.7

56.2 71.2 86.2

108.7

2.52 1.75 1.44 1.15

4.5×4.0×3.5

Sumida CDRH4D18

1.5 2.2 3.3 4.7

75 110 162

1.32 1.04 0.84

4.7×4.7×2.0

Toko D312C

1.5 2.2 3.3 4.7

120 140 180 240

1.29 1.14 0.98 0.79

3.6×3.6×1.2

Input Capacitor Selection The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. A low ESR input capacitor sized for minimum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 4.7μF ceramic capacitor for most applications is sufficient. Output Capacitor Selection The output capacitor is requires to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple VOUT is determined by:

( )OUT IN OUTOUT

IN OSC OSC

V V V 1V ESRV f L 8 f C3× − ⎛ ⎞

Δ ≤ × +⎜ ⎟× × × ×⎝ ⎠

Ordering Information

Marking Information

OCP2158XXXX

Package: TW: TSOT23-5L

Output Voltage: Blank: ADJ

12: 1.2V 15: 1.5V 18: 1.8V

Packing: Blank:Tube or Bulk

A:Tape & Reel

Temperature Grade: D: -40~85

Y: Year(9=2009)

Part Number:OCP2158

ABVYMM:Month(1-9,O,N,D)

Output Voltage: A: ADJ B: 1.2V C: 1.5V D: 1.8V

Page11 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Package Information

Dimensions In Millimeters Dimensions In Inches Symbol Min. Max. Min. Max. A 0.90 1.10 0.036 0.044

A1 0.01 0.13 0.0004 0.0052 b 0.30 0.50 0.012 0.020 C 0.09 0.20 0.0036 0.008 D 2.80 3.00 0.112 0.120 E 2.50 3.10 0.100 0.124

E1 1.50 1.70 0.060 0.068 L 0.20 0.55 0.008 0.022

L1 0.35 0.80 0.014 0.032 e 0.95 Bsc. 0.038 Bsc.

e1 1.90 Bsc. 0.076 Bsc. θ 0ο 10ο 0ο 10ο

e1

D

e b

E1 E5 4

321

A

A1

L1

L θ

C

Page12 - 12 Rev.1.0 Jan. 07, 2009

OCP2158

1.5MHz 700mA Synchronous Step-Down Converter with Low Quiescent Current

Packing Information

Package Type Carrier Width (W) Pitch (P) Reel Size(D) Packing Minimum

TSOT23-5L 8.0±0.1 mm 4.0±0.1 mm 180±1 mm 3000pcs

Note: Carrier Tape Dimension, Reel Size and Packing Minimum

D

P

W