CAT823 데이터 시트보기 (PDF) - Catalyst Semiconductor => Onsemi

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CAT823

System Supervisory Voltage Reset with Watchdog and Manual Reset

Catalyst Semiconductor => Onsemi 

CAT823, CAT824, CAT825

APPLICATION NOTES

µP’s with Bidirectional Reset Pins

The R¯¯E¯S¯E¯T¯ output can be pulled low by processors

like the 68HC11 allowing for a system reset issued by

the processor. The maximum pullup current that can

be sourced by the CAT82_L/M is 1.5mA (and by the

CAT82_T/R/S/Z/Y is 800µA) allowing the processor to

pull the output low even when the CAT82x is pulling it

high.

Power Transients

Generally short duration negative-going transients of

less than 2µs on the power supply at VRST minimum

will not cause a reset condition. However the lower

the voltage of the transient the shorter the required

time to cause a reset output. These issues can

usually be remedied by the proper location of bypass

capacitance on the circuit board.

OUTPUT VALID CONDITIONS

The R¯¯E¯S¯E¯T¯ output uses a push-pull output which can

maintain a valid output down to a VCC of 1.0 volts. To

sink current below 0.8V a resistor can be connected

from R¯¯E¯S¯E¯T¯ to Ground (see Figure 8.) This

arrangement will maintain a valid value on the R¯¯E¯S¯E¯T¯

output during both power up and down but will draw

current when the R¯¯E¯S¯E¯T¯ output is in the high state. A

resistor value of about 100kΩ should be adequate in

most situations to maintain a low condition valid

output down to VCC equal to 0V.

Figure 8. R¯¯E¯S¯E¯T¯ Valid to 0 Volts VCC

WDI

CAT823

VCC

MR

GND

RESET

100kΩ

µC

RESET

Doc. No. MD-3027 Rev. B

10

© Catalyst Semiconductor, Inc.

Characteristics subject to change without notice

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