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Notice: The information in this document is subject to change without notice

3.3V µP Power Supply Monitor and Reset Circuit

ASM1832

rev 1.5

February 2005

Detailed Description

The

ASM1832

monitors

the

microprocessor

or

microcontroller power supply and issues reset signals, both

active HIGH and active LOW, that halt processor operation

whenever the power supply voltage levels are outside a

predetermined tolerance.

RESET and RESET outputs

RESET and RESET signals are active for a minimum of

250ms after the supply has returned to in-tolerance level.

This allows the power supply and monitored processor to

stabilize before instruction execution is allowed to begin.

Trip Point Tolerance Selection

below 3.3V without asserting a reset. With TOL conected to

below 2.64V. RESET and RESET become active when the

and RESET remain active for a minimum time period of

threshold RESET stays LOW and is guaranteed to be 0.4V or

ASM1832 uses a push-pull drive stage that can maintain a

a resistor can be connected from the reset pin (RESET) to

Ground. This configuration will give a valid value on the reset

down, the configuration will draw current when the RESET is

in the high state. The value of 100K

Ω should be adequate to

maintain a valid condition. The active HIGH reset signal is

.

Application Information

Manual Reset Operation

Push-button switch input, PBRST, allows the user to override

the internal trip point detection circuits and issue reset

Microprocessor

RESET

RESET

ASM1832

100kΩ

Tolerance

Select

Tolerance

TRIP Point Voltage

(V)

Min

Nom

Max

20%

2.47

2.55

2.64

TOL = GND

10%

2.80

2.88

2.97

~~

~~

RESET

RESET

Figure 1: Timing Diagram : Power Up

~~

~~

RESET

RESET

Figure 2: Timing Diagram : Power Down