ASM802M datasheet(2/13 Pages) ALSC

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

ASM690A / 692A

ASM802L / 802M

ASM805L

µP Power Supply Supervisor With Battery Backup Switch

rev 1.0

October 2003

Pin Configuration

VOUT

VCC

GND

PFI

VBATT

RESET (RESET)

WDI

PFO

Plastic/CerDip/SO

ASM690A

ASM692A

ASM802L

ASM802M

(ASM805L)

Pin Description

Pin Number

Name

Function

ASM690A /

ASM692A

ASM802L /

ASM802M

ASM805L

VOUT

Voltage supply for RAM. When VCC is above the reset threshold, VOUT connects to

VCC through a P-Channel MOS device. If VCC falls below the reset threshold, this

output will be connected to the backup supply at VBATT (or VCC, whichever is

higher) through the MOS switch to provide continuous power to the CMOS RAM.

VCC

+5V power supply input.

GND

Ground

PFI

Power failure monitor input. PFI is connected to the internal power fail comparator

which is referenced to 1.25V. The power fail output (PFO) is active LOW but

remains HIGH if PFI is above 1.25V. If this feature is unused, the PFI pin should be

connected to GND or VOUT.

PFO

Power-fail output. PFO is active LOW whenever the PFI pin is less than 1.25V.

WDI

Watchdog input. The WDI input monitors microprocessor activity. An internal timer

is reset with each transition of the WDI input. If the WDI is held HIGH or LOW for

longer than the watchdog timeout period, typically 1.6 seconds, RESET (or RESET)

is asserted for the reset pulse width time, tRS, of 140ms, minimum.

RESET

Active-LOW reset output. When triggered by VCC falling below the reset threshold

or by watchdog timer timeout, RESET (or RESET) pulses low for the reset pulse

width tRS, typically 200ms. It will remain low if VCC is below the reset threshold

(4.65V in ASM690A / ASM802L and 4.4V in the ASM692A / ASM802L) and

remains low for 200ms after VCC rises above the reset threshold.

RESET

Active-HIGH reset output. The inverse of RESET.

VBATT

Auxiliary power or backup-battery input. VBATT should be connected to GND if the

function is not used. The input has about 40mV of hysteresis to prevent rapid tog-

gling between VCC and VBATT.

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