MAX6369 Datasheet, PDF (6/8 Pages) Maxim Integrated Products – Pin-Selectable Watchdog Timers

Pin-Selectable Watchdog Timers
V_CC
WDI
MAX6369–MAX6374
TRANSITION
DETECTOR
EN
SET 2
SET 1
CONTROL
LOGIC
ENABLE
CLEAR
SET 0
SET WATCHDOG TIMEOUT
OUT
OUTPUT
WDO
SET STARTUP DELAY
WATCHDOG
TIMER CIRCUITRY
GND
Figure 1. Functional Diagram
V_CC
t_SETUP
t_DELAY
t_WD
t_WD
t_WD
WDI
AA
B
C
D
EF G
E
WDO
t_WDO
A TRANSITIONS ON WDI IGNORED DURING SETUP DELAY.
B TRANSITION(S) ON WDI IGNORED DURING STARTUP DELAY PERIOD.
C WATCHDOG TIMER STARTS AFTER STARTUP DELAY AND WDO IS DEASSERTED.
D TRANSITION OCCURS BEFORE WATCHDOG TIMEOUT PERIOD. WATCHDOG
TIMER CLEARS AND STARTS TIMER AGAIN.
E WATCHDOG TIMES OUT, WDO ASSERTS.
F TRANSITIONS ON WDI IGNORED WHEN WDO ASSERTED.
G WATCHDOG TIMER STARTS AFTER WDO DEASSERTS.
Figure 2. Watchdog Timing
• 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
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