Low-Power µP Supervisory Circuits with

Battery-Backup Circuit and Chip-Enable Gating

10

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Pin Description—MAX16020/MAX16021

PIN

MAX16020

MAX16021

NAME

FUNCTION

1

1

BATT

GND with a 0.1µF capacitor.

22

MR

Active-Low Manual Reset Input. RESET asserts when MR is pulled low. RESET remains low

for the duration of reset timeout period after MR transitions from low to high. Connect MR to

OUT or leave unconnected if not used. MR is internally connected to OUT through a 30k

Ω

pullup resistor.

3

3

PFI

Power-Fail Comparator Input. Connect PFI to a resistive divider to set the desired PFI

hysteresis provides noise immunity. The power-fail comparator is powered from OUT.

4

4

WDI

Watchdog Timer Input. If WDI remains high or low for longer than the watchdog timeout

clears when reset asserts or whenever WDI sees a rising or falling edge. To disable the

watchdog feature, leave WDI unconnected or three-state the driver connected to WDI.

55

LL

to generate a nonmaskable interrupt (NMI) to initiate an orderly shutdown routine when

6

—

BATT_TEST

Open-Drain Battery-Test Output. Pulses low for 1.3s every 24 hours during the battery

load during the battery test.

—

6

RESET

threshold and MR deasserts.

7

7

BATTOK

Battery-OK Output. BATTOK goes low when the battery voltage falls below the BATTOK

threshold (BATTOK is low when in battery-backup mode).

8

8

BATTON

Active-High Battery-On Output. BATTON goes high when in battery-backup mode.