Linear Technology CorporationLT3070 Backgrounder

Steve KnothSenior Product Marketing Engineer

© 2006 Linear Technology

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Agenda

Background• Past Limitations for LDOs Powering

FPGAs/ASICs• Advantages of Next Gen Linear Tech LDOs

LT3070• Definition• Features & Benefits• Application Circuits• Target Markets• Target Applications

© 2006 Linear Technology

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Power Business Unit

• Products:– Switching Regulators, DC/DC Controllers,

Charge-Pumps, Linear Regulators, Battery Chargers, PMICs, LED Drivers, DC Power Switches

• Markets:Handheld Battery Powered Products – Cell

Phones, Digital Still Cameras, PDAs, MP3 Players, PNDs, etc.

Industrial Control and InstrumentationAutomotive – Navigation and InfotainmentTelecommunications – InfrastructureComputer – Servers, Workstations and

Notebook PC

© 2006 Linear Technology

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Traditional Limitations for in Powering FPGAs/DSPs/ASICs/µPs

For high-performance digital ICs such as FPGAs, DSPs, µP’s, µC’s and ASICs, the trend is for higher currents and lower voltages. More efficient, switching regulators have traditionally been used to power these devices but there are noise and layout limitations, so LDOs have come into play.

The LDO must have:

• Operation over a wide input/output voltage range• High output current capability• Low output noise• Low dropout operation • Excellent thermal performance• Fast response time• High PSRR• System debugging features a “+” plus

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© 2006 Linear Technology

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LT3070: What is It? UltraFast™ 5A LDO

© 2006 Linear Technology

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LT3070: What is It? UltraFast 5A LDO

5A, Low Noise,

Programmable Output,

85mV Dropout

Linear Regulator• New NMOS LDO Family:

Low Noise, Programmable Output, High BW

• Wide VIN Range: 0.95V to 3V

• Ultra-Low Output Voltage Noise: 25µVRMS (10Hz to 100kHz)

• Wide VOUT Range: 0.8V to 1.8V in 50mV increments

• Fast Transient Response• Digital Margining for System Debug

© 2006 Linear Technology

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LT3070: Block Diagram

The LT3070’s architecture drives an internal N-channel power MOSFET as a source follower. This configuration permits a user to realize an extremely low

dropout, ultra- fast transient response regulator with excellent high frequency PSRR performance.

© 2006 Linear Technology

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LT3070: Key Technical Features *

• Output Current: 5A• Dropout Voltage: 85mV Typical

• Digitally Programmable VOUT: 0.8V to 1.8V in 50mV steps

• Digital Output Margining: ±1%, ±3% or ±5%• ±1% Accuracy Over Line, Load and Temperature (Initial =

0.2%)

• Low Output Noise: 25μVRMS (10Hz to 100kHz)

• Parallelable: Use Two for a 10A Output• 28-Lead (4mm × 5mm) QFN Package

* Specifications subject to change

© 2006 Linear Technology

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LT3070: Other Features *• Stable with Low ESR Ceramic Output Capacitors (15μF

Min)• High Frequency PSRR: 30dB at 1MHz• VIOC Pin Controls Upstream Buck Converter to Maintain

LowPower Dissipation and Optimize Efficiency

• PWRGD/UVLO Flag• REF/BYP Pin: Single Cap provides programmable soft-

start and lowers output noise• Enable Function Turns Output On/Off• Current Limit Foldback Protection• Thermal Shutdown

* Specifications subject to change

© 2006 Linear Technology

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LT3070: Features & Benefits

FEATURES BENEFITS

Ultra-Low Dropout Voltage: 85mV High efficiency, low Vin to low Vout conversion, reduces power dissipation

Ultra-Low Noise: 25µVRMS

(10Hz to 100kHz)

Great for powering noise-sensitive supply rails or for post-regulating switchers

Digitally Programmable Vout: 0.8V to 1.8V in 50mV increments

Precision output voltage set capability

Digital Margining: ±1%, ±3%, ±5% Helpful to determine system tolerance during debug phase

Wide Input Voltage Range: 1V to 3V Flexibility, penetration into a wide variety of end markets/applications

2 Devices May be Paralleled (10A) Higher-current capability than a single LDO can provide; spreads heat across a PCB

Fast Transient Response Maintains output voltage stability during fast events

Reverse Current Protection, Current Limit with Power Foldback, Thermal Shutdown, UVLO

Bulletproof protection for the IC and the load

Thermally Efficient Package:4mmx5mm QFN-28, ThetaJA=30°C/W

Small package provides plenty of current in a small footprint with great thermal performance

© 2006 Linear Technology

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LT3070: Package/Pinout

© 2006 Linear Technology

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LT3070 Typical Application Circuit

Pin-selectable VOUT

Digital Margining SelectSoft Start Control

Small Output Caps!!!

Power Good Indicator

© 2006 Linear Technology

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LT3070 Post-Buck Regulator Application

Maintain a constant “VIN – VOUT” across the LDO by adjusting the VITH / VC pin regulation point

1.3V / 7A

VBIAS 3.3V

PGOOD

0.01µFX7R

VOUT

2.2µF

47µF

50K

LOAD

1

50K

2.2 + 4.7 + 10µFX7R, 0805

100µF, 6.3V(x3)

PLLLPF

MODE

PHMODE

TRACK

V

PGOOD

BSEL

MGN

LTC3415EUHF

RUN PVCLKOUT SV

SW

SW

PGND

SGND

IN IN ITHITHM

CLKIN

PVIN

SW

SW

NC

SW

SW

SW

SW

PGND PGNDPGNDPGNDPGND PGND

PVIN

PVIN

FB

PVIN

PVIN

NC

PGND

0.2µH

47µF

(x3)6.3V

15K

20K

0.1µF

10pF100pF

15K

1.0V / 5A

NC

NC

NC

NC

Notes:LTC3415 Switcher 2MHz internal oscillator

PWRGD

VIOC

OUTIN

GND

BIAS

REF/BYP

VO2

VO1

VO0

EN SENSE

LT3070

MARGTOL

MARGSEL

100pF

4.7nF

SGND

2K

Optimal Efficiency across LDO

© 2006 Linear Technology

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LT3070 Current Sharing Application

1.32V / 7A

VBIAS 3.3V

PGOOD

0.01µFX7R

VOUT

2.2µF

47µF

50K

0.01µFX7R

2.2µF

P.O.L. 1

VOUTP.O.L. 2

1 50K

2.2 + 4.7 + 10µFX7R, 0805

2.2 + 4.7 + 10µFX7R, 0805

R2mΩ

TRACE

1V POW

ER PLAN

E

controlled

R2mΩ

TRACE

controlled

100µF, 6.3V(x3)

PLLLPF

MODE

PHMODE

TRACK

V

PGOOD

BSEL

MGN

LTC3415EUHF

RUN PVCLKOUT SV

SW

SW

PGND

SGND

IN IN ITHITHM

CLKIN

PVIN

SW

SW

NC

SW

SW

SW

SW

PGND PGNDPGNDPGNDPGND PGND

PVIN

PVIN

FB

PVIN

PVIN

NC

PGND

0.2µH

47µF

(x3)6.3V

47µF

50K

15K

18K

0.1µF

10pF100pF

15K

1.0V / 5A

1.0V / 5A

SGND

NC

NC

NC

NC

NC

NC

NC

NC

Notes:LTC3415 Switcher 2MHz internal oscillator

PWRGD

VIOC

OUTIN

GND

BIAS

REF/BYP

VO2

VO1

VO0

EN SENSE

LT3070(2)

MARGTOL

MARGSEL

PWRGD

VIOC

OUTIN

GND

BIAS

REF/BYP

VO2

VO1

VO0

EN SENSE

LT3070(1)

MARGTOL

MARGSEL

4.7nF

Achieve 10A load current capability…or more!

© 2006 Linear Technology

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LT3070: Typical Applications/Target End Markets

• FPGA and DSP Supplies

• ASIC and Microprocessor Supplies

• Servers and Storage Devices

• Sensitive Communication Supplies

• Supply Isolation

• Post Buck Regulation

© 2006 Linear Technology

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© 2006 Linear Technology

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LT3070: Conclusion• Requirements for LDOs Powering High Performance Digital ICs:

• Operation over a wide input/output voltage range with high output current capability

• Low output noise

• Low dropout operation

• Excellent thermal performance

• Fast response time and high PSRR

• System debugging features a “+” plus

LT3070 UltraFast 5A Ultra-Low Dropout, Low Noise LDO:• Dropout Voltage: 85mV Typical

• Digitally Programmable VOUT: 0.8V to 1.8V

• Digital Output Margining: ±1%, ±3% or ±5%

• ±1% Accuracy Over Line, Load and Temperature

• Low Output Noise: 25μVRMS (10Hz to 100kHz)

• Parallelable: Use Two for a 10A Output

• 28-Lead (4mm × 5mm) QFN Package