Datasheet

LT3689/LT3689-5
27
3689fe
For more information www.linear.com/LT3689
APPLICATIONS INFORMATION
(14a) W/T = High. The First Valid Negative Edge on WDI Must Occur Before the Watchdog Timer Expires
(14b) W/T = High. Subsequent Edges Must Occur Before the Timer Expires
(14c) W/T = Low. Restart Sequence After a Timing Fault
Figure 14. W/T = High. Time Charts for the Power-On-Reset and Watchdog Timer in Timer Mode
FB
0.72V
CPOR
CWTD
RST
WDO
RST COUNTER
WDT COUNTER
1
1 2 30 31 32
3689 F14a
0.2V
0.2V
2
t
RST
3 4
t
WDU
WATCH DOG INPUT MUST
TRANSITION LOW AT LEAST
ONCE IN THIS PERIOD
WATCH DOG INPUT
IS IGNORED
• • •
WDI
CWDT
0.2V
3689 F14b
1 2 30 31 32
WDO
WDT COUNTER
t
WDU
• • •
WATCH DOG INPUT MUST
TRANSITION LOW AT LEAST
ONCE IN THIS PERIOD
CPOR
CWTD
WDO
RST COUNTER
WDT COUNTER
1
1 2 30 31 32
0.2V
0.2V
3689 F14c
2
t
RST
3 4
t
WDU
WATCH DOG INPUT MUST
TRANSITION LOW AT LEAST
ONCE IN THIS PERIOD
WATCH DOG INPUT
IS IGNORED
• • •