ASM1832

http://onsemi.com

4

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

250 ms 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 3.3 V without asserting a reset. With TOL connected

falls below 2.64 V. RESET and RESET become active when

RESET and RESET remain active for a minimum time

the reset threshold RESET stays LOW and is guaranteed to

output on the ASM1832 uses a push−pull drive stage that can

maintain a valid output below 1.2 V. To sink current with

pin (RESET) to Ground. This configuration will give a valid

both power up and down, the configuration will draw current

when the RESET is in the high state. The value of 100 K

W

should be adequate to maintain a valid condition. The active

Table 4.

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

Figure 3.

Figure 4. Timing Diagram: Power Up

Figure 5. 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 signals. The pushbutton input is debounced and is

pulled HIGH through an internal 40 k

W resistor.

both resets become active and remain active for a minimum

time period of 250 ms after PBRST returns HIGH.

The debounced input is guaranteed to recognize pulses

greater than 20 ms. No external pull−up resistor is required,

since PBRST is pulled HIGH by an internal 40 k

W resistor.

The PBRST can be driven from a TTL or CMOS logic line

or shorted to ground with a mechanical switch.