LTC2924

1

2924fa

Quad Power Supply

Sequencer

use with external N-channel MOSFETs or power supplies

with shutdown pins. Four power supplies can be fully

sequenced by a single LTC2924 and up to five supplies

can be sequenced to a sixth master supply. The LTC2924

requires a minimum of external components, using only

two feedback resistors per sequenced power supply and

a single resistor to set hysteresis.

An internally regulated charge pump provides gate drive

voltages for external logic and sub-logic-level MOSFETs.

Adding a single capacitor enables an adjustable time delay

between power supplies during both Power On and Power

Offsequencing.Asecondcapacitorcanbeaddedtoenable

a power good timer for detecting the failure of any power

supply to turn on within the selected time. Errors in power

supply sequencing and the control input are detected and

reported at the FAULT output. The LTC2924 features pre-

cision input comparators which can provide 1% accuracy

in monitoring power supply voltages.

Multiple LTC2924s may be easily cascaded to sequence

a virtually unlimited number of power supplies.

Power-Up Sequence

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

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

All other trademarks are the property of their respective owners.

■

Fully Sequence and Monitor Four Supplies

– Six with Minimal External Circuitry

■

Cascadable for Additional Supplies

■

Power Off in Reverse Order or Simultaneously

■

Charge Pump Drives External MOSFETs

■

Drives Power Supply Shutdown Pins with No

External Pull-Up Resistors

■

10µA Output Current Allows Soft-Starting of Supplies

■

Done Indicator for Both Power On and Power Off

■

Adjustable Time Delay Between Power Supplies

■

Power Good Timer

■

Power Supply Voltage Monitoring and Power

Sequence Error Detection and Reporting

■

Available in a 16-Lead Narrow SSOP Package

■

Sequenced Power Supplies for ASICs with Multiple

I/O and Core Voltages

■

Latch-Up Prevention in Systems with Multiple Power

Supplies

APPLICATIO S

OUT1

OUT2

OUT3

OUT4

ON

DONE

FAULT

TMR

PGT

IN1

IN2

IN3

IN4

HYS/CFG

LTC2924

GND

150nF

2924 TA01a

SYSTEM

CONTROLLER

150nF

1.69k

6.04k

0.1

µF

Q1

Q2

100k

1.62k

66.5k

18.2k

3.09k

Q1-Q4: IRL3714S

ALL RESISTORS 1%

20k

49.9k

10k 10k

5V

3V

1V

3.3V

SHDN

5V

SHDN

5V EARLY

2V/DIV

2V/DIV

10ms/DIV

2924 TA01b

5V

3V

1V

3.3V

ON

TMR

DONE

5V/DIV

5V/DIV

2V/DIV

2V/DIV

10ms/DIV

2924 TA01c

5V

3V

1V

3.3V

ON

TMR

DONE

5V/DIV

5V/DIV

Power-Down Sequence