LTC2924C(RevA) データシートの表示（PDF） - Linear Technology

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LTC2924C
(Rev.:RevA)

Quad Power Supply Sequencer

Linear Technology 

LTC2924

APPLICATIO S I FOR ATIO

a Power On sequence (VON) and Off during a Power Off

sequence (VOFF).

Referring to Figures 5 and 6, each set of resistors can

then be calculated by:

RB

=

VON – VOFF

IHYS

RA

=

RB • 0.61V

VON – 0.61V

In the following example (Figure 5) IHYS is 50µA. This

corresponds to a RHYS resistor of:

IHYS

VPS

VON = 2.2V

VOFF = 1V

IHYS RB

IRB

IN

RA

IFB = IRB + IHYS

+– 0.61V

2924 F05

Figure 5. Designing IHYS, Feedback Resistors

RHYS

=

0.5V

50µA

=

10kΩ

In Figure 5, VON = 2.2V and VOFF = 1V. Using the equations

provided above:

RB

=

2.2V – 1V

50µA

=

24kΩ

RA

=

24kΩ • 0.61V

2.2V – 0.61V

=

9.2kΩ

Hysteresis Voltage Check

After calculating the resistors RB and RA, check to make

sure the hystersis voltage at the ON and IN1-IN4 pins is

greater than 4mV. Use the following equation:

( ) VHYS =

VON – VOFF • RA

RA + RB

For this example:

VHYS

=

(2.2V – 1V) • 9.2kΩ

9.2kΩ + 24kΩ

=

0.33V

which is greater than 4mV.

POWER SUPPLY 1

3.3V

SHDN

POWER SUPPLY 2

5V

SHDN

POWER SUPPLY 3

1.6V

SHDN

5V EARLY*

POWER SUPPLY 4

10k 10k

2.5V

SHDN

0.1µF

VCC

OUT1

IN1

LTC2924

OUT2

IN2

24.9k

OUT3

IN3

OUT4

IN4

SYSTEM

CONTROLLER

ON

DONE

FAULT

9.31k

*5V EARLY MUST BE ON BEFORE

SEQUENCING SUPPLIES

150nF

150nF

TMR

HYS/CFG

PGT GND

49.9k

2924 TA03

Figure 6. Typical Power Supply Sequencer

15.8k

11.81k

49.9k

7.87k

VON ≥ 3.01V

VOFF ≤ 2.68V

VON ≥ 4.49V

VOFF ≤ 3.99V

VON ≥ 1.43V

VOFF ≤ 1.27V

VON ≥ 2.25V

VOFF ≤ 2V

33.2k

8.45k

10

2924fa

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