TPS3813J25, TPS3813L30
TPS3813K33, TPS3813I50
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SLVS331B – DECEMBER 2000 – REVISED JUNE 2005
If the window watchdog ratio pin (WDR) is set to V
DD
, Position 1 in
then the lower window frame is a
value based on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT)
connected to GND, it is a ratio of 1:124.9, for WDT connected to V
DD
, it is a ratio of 1:127.7, and for an external
capacitor connected to WDT, it is a ratio of 1:64.5.
If the window watchdog ratio pin (WDR) is set to GND, Position 2, the lower window frame will be a value based
on a ratio calculation of the overall window timeout size: For the watchdog timeout pin (WDT) connected to GND,
it will be a ratio of 1:31.8, for WDT connected to V
DD
it will be 1:32, and for an external capacitor connected to
WDT it will be 1:25.8.
The watchdog timeout can be set in two fixed timings of 0.25 seconds and 2.5 seconds for the window or can by
programmed by connecting a external capacitor with a low leakage current at WDT.
Example: If the watchdog timeout pin (WDT) is connected to V
DD
, the timeout will be 2.5 seconds. If the window
watchdog ratio pin (WDR) is set in this configuration to a ratio of 1:127.7 by connecting the pin to V
DD
, the lower
boundary is 19.6 ms.
V
DD
0.1
µF
V
DD
Position 1
See Note A
Position 2
See Note B
Position 4
See Note D
C
(ext)
Position 5
See Note E
Position 3
See Note C
V
DD
WDR
0.1
µF
R
V
DD
RESET
TPS3813
WDT
GND
WDI
I/O
GND
RESET
uC
V
DD
A.
B.
C.
D.
Watchdog window ratio
Watchdog timeout set to typical 2.5 sec
Watchdog timeout programmed by external capacitor
Watchdog timeout set to typical 0.25 sec
Figure 2. Application Example
6
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