L4902A 데이터 시트보기 (PDF) - STMicroelectronics

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L4902A

DUAL 5V REGULATOR WITH RESET AND DISABLE

STMicroelectronics 

L4902A

Configurations of this type are used in products

where the OFF switch is part of a keyboard

scanned by a micro which operates continuously

even in the OFF state.

Another application for the L4902A is supplying a

shadow-ram microcomputer chip (SGS M38SH72

for example)where a fast NV memory is backedup

on chip by a EEPROMwhen a low level on the reset

output occurs.

By adding two CMOS-SCHMIDT-TRIGGER and

few external components, also a watch dog func-

Figure 4

tion may be realized (see Figure 5). During normal

operation the microsystem supplies a periodical

pulse waveform;if an anomalousconditionoccours

(in the program or in the system), the pulses will be

absent and the disable input will be activated after

a settling time determined by R1 C1. In this condi-

tion all the circuitry connected to V02 will be dis-

abled, the system will be restarted with a new reset

front.

The disable of V02 prevent spurious operation dur-

ing microprocessor malfunctioning.

Figure 5

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