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Fabricante

LTC2924CGN

Quad Power Supply Sequencer

Linear Technology 

LTC2924

Applications Information

Up to five supplies can be sequenced to a sixth master

supply by a single LTC2924 (Figure 4). The turn on of the

first power supply is sensed by the ON pin. Power supplies

two through five are enabled by the OUT1 through OUT4

pins, and their turn on sensed by the IN1 through IN4 pins

respectively. The last power supply is enabled by the DONE

pin, which is generally connected through an inv­ erter. This

application is used where power supplies are sequentially

sequenced on and the turn off is simulta­neous. Multiple

LTC2924s can be cascaded to facilitate sequencing of

eight or more power supplies. See the Cascading Multiple

LTC2924s section.

Selecting the Hysteresis Current and IN Pin Feedback

Resistors

The IN1-IN4 pins are connected to a sequenced power

supply with a resistive divider. The resistors are calculated

by first selecting a hysteresis current, IHYS, and calculat-

ing RHYS:

RHYS

=

0.5V

IHYS

;

0.5µA

≤ IHYS

≤

50µA

For each sequenced power supply, choose a voltage

when the power supply is considered to be On during

PS1

SHDN VOUT

PS2

SHDN VOUT

PS3

SHDN VOUT

PS4

SHDN VOUT

PS5

SHDN VOUT

10

PS6

SHDN VOUT

VCC EARLY*

SYSTEM

CONTROLLER

TURN OFF

*VCC EARLY MUST BE ON BEFORE

SEQUENCING SUPPLIES

VCC

OUT1

ON

LTC2924

OUT2

IN1

OUT3

IN2

OUT4

IN3

DONE

IN4

FAULT

GND

2924 F04

Figure 4. 6-Power Supply Sequencer Block Diagram

For more information www.linear.com/LTC2924

2924fc

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