ASM1832SF 查看數據表（PDF） - Alliance Semiconductor

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ASM1832SF

3.3V µP Power Supply Monitor and Reset Circuit

Alliance Semiconductor 

February 2005

rev 1.5

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

The TOL input is used to determine the level VCC can vary

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

VCC, RESET and RESET become active whenever VCC falls

below 2.64V. RESET and RESET become active when the

VCC falls below 2.98V if TOL is connected to ground.

After VCC has risen above the trip point set by TOL, RESET

and RESET remain active for a minimum time period of

250ms. On power-down, once VCC falls below the reset

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

less until VCC drops below 1.2V. The reset output on the

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

valid output below 1.2V. To sink current with VCC below 1.2V,

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

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

output with VCC approaching 0V. During both power up and

down, the configuration will draw current when the RESET is

in the high state. The value of 100KΩ should be adequate to

maintain a valid condition. The active HIGH reset signal is

valid down to a VCC level of 1.2V also.

ASM1832

RESET

Microprocessor

RESET

100kΩ

ASM1832

.

Tolerance

Select

TOL = VCC

TOL = GND

Tolerance

TRIP Point Voltage

(V)

Min Nom Max

20%

2.47 2.55 2.64

10%

2.80 2.88 2.97

~~ VCCTP(MIN)

VCC

tR

VCCTP(MAX)

VCCTP

tRPU

~~

Figure 1: Timing Diagram : Power Up

VOH

RESET

VOL

RESET

VCC

tF

VCCTP (MAX)

VCCTP

VCCTP (MIN)

RESET

~~

tRPD

RESET

VOH

VOL

~~

Figure 2: Timing Diagram : Power Down

Application Information

Manual Reset Operation

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

the internal trip point detection circuits and issue reset

3.3V µP Power Supply Monitor and Reset Circuit

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

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