GS-R51515S View Datasheet(PDF) - STMicroelectronics

Part Name

Description

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GS-R51515S

31W TRIPLE OUTPUT STEP-DOWN SWITCHING REGULATORS

STMicroelectronics 

GS-R51212S/GS-R51515S

USER NOTES

Input Voltage

The recommended operating maximum DC input

voltage is 40V inclusive of the ripple voltage. The

use of an external low ESR, high ripple current

capacitor located as close the module as possible

is recommended; suggested value is 100µF/50V.

Soft-start

To avoid heavy inrush current the output voltage

rise time is typically 10ms in any condition of load.

Power Fail-Reset Circuit

The module include a voltage sensing circuit that

may be used to generate a power-on/power-off

reset signal for a microprocessor system.

The circuit sense the input supply voltage and the

output generated voltage Vo1 (+5V) and will gener-

ate the required reset signal only when both the

sensed voltages have reached the required value

for correct system operation.

When both the supply voltage and the regulated

voltage are in the correct range the output Reset

signal is generated after a delay time tDR of 100ms

typical.

A latch assures that if a spike is present on the

sensed voltage the delay time circuit discharges

completely before initialization of a new reset cycle.

Reset output has internal pull-up resistor of

10kOhm connected to Vo +5V pin.

Maximum sink output current is 20mA at

VRESET(sat) = 200mV.

Fig. 1 and fig. 2 show reset waveforms.

Power Fail Programmable Input

This pin is internally connected via a divider to the

+Vin pin for Power Fail function.

The factory setting is for a value of 11V with 1V

hysteresis.

It is possible to program a different value of Power

Fail threshold by connecting a resistor (Rpf) be-

tween pin 3 (Power Fail Input) and pin 1 (GND

Input). The value of Rpf must be calculated accord-

ing to the following formula:

Rpf =

5.1

= (kΩ)

Vpf − 5.1 − 0.191

34

where Vpf is the desired value of Power Fail thresh-

old voltage.

Exampe: Vpf = 24V (must not be lower than 12V):

Rpf =

5.1

= 14kΩ

24 − 5.1 − 0.191

34

Figure 1 - Reset and Power Fail waveforms.

5/8

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