Pin-Selectable Watchdog Timers

6

_______________________________________________________________________________________

• Watchdog Timeout Period:

Normal operating watchdog timeout period after the

initial startup delay.

A watchdog output pulse is asserted if a valid watch-

dog input transition is not received before the timeout

period elapses.

Eight pin-selectable timeout period options for each

device, from 30µs to 60s.

Pin-selectable watchdog timer disable feature.

• Watchdog Output/Timing Options:

Open drain, active low with 100ms minimum watch-

dog output pulse (MAX6369/MAX6371/MAX6373).

Push-pull, active low with 1ms minimum watchdog

output pulse (MAX6370/MAX6372/MAX6374).

Each device has a watchdog startup delay that is initi-

ated when the supervisor is first powered or after the

user modifies any of the logic control set inputs. The

watchdog timer does not begin to count down until the

WDI

WDO

A

B

C

D

E

F

G

TRANSITIONS ON WDI IGNORED DURING SETUP DELAY.

TRANSITION(S) ON WDI IGNORED DURING STARTUP DELAY PERIOD.

WATCHDOG TIMER STARTS AFTER STARTUP DELAY AND WDO IS DEASSERTED.

TRANSITION OCCURS BEFORE WATCHDOG TIMEOUT PERIOD. WATCHDOG

TIMER CLEARS AND STARTS TIMER AGAIN.

WATCHDOG TIMES OUT, WDO ASSERTS.

TRANSITIONS ON WDI IGNORED WHEN WDO ASSERTED.

WATCHDOG TIMER STARTS AFTER WDO DEASSERTS.

A

AB

C

D

EF

G

E

Figure 2. Watchdog Timing

WATCHDOG

TIMER CIRCUITRY

TRANSITION

DETECTOR

ENABLE

SET WATCHDOG TIMEOUT

SET STARTUP DELAY

MAX6369–MAX6374

EN

CONTROL

LOGIC

SET 2

SET 1

SET 0

GND

CLEAR

WDO

OUT

WDI

OUTPUT

Figure 1. Functional Diagram