LTC2925

1

2925f

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO S

The LTC

tracking and sequencing requirements. By selecting a few

resistors, the supplies can be configured to ramp-up and

ramp-down together or with voltage offsets, time delays

or different ramp rates.

The LTC2925 controls the outputs of three independent

supplies without inserting any pass element losses. For

systems that require a fourth supply, or when a supply

does not allow direct access to its feedback resistors, one

supply can be controlled with a series FET. When the FET

is used, an internal remote sense switch compensates for

the voltage drop across the FET and current sense resistor,

and an electronic circuit breaker provides protection from

short-circuit conditions.

The LTC2925 also includes a power good timeout feature

that turns off the supplies if an external supply monitor

fails to indicate that the supplies have entered regulation

within an adjustable time-out period.

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Microprocessor, DSP and FPGA Supplies

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Servers

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Communication Systems

, LTC and LT are registered trademarks of Linear Technology Corporation.

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Flexible Power Supply Tracking Up and Down

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Power Supply Sequencing

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Supply Stability Is Not Affected

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Controls Three Supplies Without Series FETs

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Controls an Optional Fourth Supply With a

Series FET

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Electronic Circuit Breaker

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Remote Sense Switch Compensates for Voltage

Drop Across a Series FET

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Supply Shutdown Outputs

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FAULT Output

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Adjustable Power Good Timeout

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Available in Narrow 24-Lead SSOP and Tiny 24-Lead

QFN Packages

Multiple Power Supply

Tracking Controller with

Power Good Timeout

0.015

Ω

Si4412ADY

0.1

µF

0.1

µF

0.82

µF

10k

3.3V

3.3V

154k

1.65k

88.7k

41.2k

2.5V

SLAVE2

MASTER

88.7k

41.2k

86.6k

100k

13k

100k

RAMPBUF

TRACK1

TRACK2

TRACK3

FB2

GATE

LTC2925

PGTMR

0.082

µF

SDTMR

0.47

µF

SCTMR

GND

2925 TA01

RAMP

100k

1.5V

SLAVE3

86.6k

DC/DC

IN

FB = 0.8V

OUT

DC/DC

IN

FB = 0.8V

RUN/SS

RUN/SS

OUT

FB3

SD3

SD2

3.3V

PGI

35.7k

10

Ω

1.8V

SLAVE1

16.5k

SUPPLY

MONITOR

DC/DC

IN

FB = 1.235V

RUN/SS

OUT

FB1

SD1

FAULT

ON

10k

STATUS

REMOTE

RST

1V/DIV

3.3V

2.5V

1.8V

1.5V

10ms/DIV

2925 TA02a

1V/DIV

3.3V

2.5V

1.8V

1.5V

2925 TA02b

10ms/DIV