Datasheet

Pin-Selectable Watchdog Timers
• 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
V
CC
WDI
WDO
t
SETUP
t
DELAY
t
WD
t
WD
t
WD
t
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.
AABCD
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
V
CC
GND
CLEAR
WDO
OUT
WDI
OUTPUT
Figure 1. Functional Diagram
6
Maxim Integrated
MAX6369–MAX6374