Datasheet
Table Of Contents
- FEATURES
- APPLICATIONS
- DESCRIPTION
- PACKAGE AND ORDERING INFORMATION
- ABSOLUTE MAXIMUM RATINGS
- RECOMMENDED OPERATING CONDITIONS Pull-up resistor value to ROC table for RESET the Pull-up resistor value row in the ROC table
- ELECTRICAL CHARACTERISTICS
- TIMING REQUIREMENTS
- SWITCHING CHARACTERISTICS
- PIN CONFIGURATIONS
- TYPICAL CHARACTERISTICS
- DETAILED DESCRIPTION
- REVISION HISTORY
Window Frame to Reset the WDI
t
boundary,
min
t
boundary,
max
t
boundary,
typ
Detection of
Rising Edge
WDI
t
t
window,
min
t
window,
typ
t
window,
max
TPS3813J25, TPS3813L30
TPS3813K33, TPS3813I50
SLVS331G –DECEMBER 2000–REVISED OCTOBER 2013
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DETAILED DESCRIPTION
IMPLEMENTED WINDOW-WATCHDOG SETTINGS
There are two different ways to set up the watchdog window. The first way is to use the implemented timing
which is a default setting. Or, the default settings can be activated by wiring the WDT and WDR pin to V
DD
or
GND. There is a total of four different timings available with these settings. They are listed in the table below.
SELECTED OPERATION MODE WINDOW FRAME LOWER WINDOW FRAME
Max = 0.3 s Max = 9.46 ms
WDR = 0 V Typ = 0.25 s Typ = 7.86 ms
Min = 0.2 s Min = 6.27 ms
WDT = 0 V
Max = 0.3 s Max = 2.43 ms
WDR = V
DD
Typ = 0.25 s Typ = 2 ms
Min = 0.2 s Min = 1.58 ms
Max = 3 s Max = 93.8 ms
WDR = 0 V Typ = 2.5 s Typ = 78.2 ms
Min = 2 s Min = 62.5 ms
WDT = V
DD
Max = 3 s Max = 23.5 ms
WDR = V
DD
Typ = 2.5 s Typ = 19.6 ms
Min = 2 s Min = 15.6 ms
To visualize the values named in the table, a timing diagram was prepared. It is used to describe the upper and
lower boundary settings. For an application, the important boundaries are the t
boundary,max
and t
window,min
. Within
these values, the watchdog timer should be retriggered to avoid a timeout condition or a boundary violation in the
event of a trigger pulse in the lower boundary. The values in the table above are typical and worst case
conditions. They are valid over the whole temperature range of –40°C to +85°C.
In the shaded area of Figure 7, it cannot be predicted if the device will detect a violation or not and release a
reset. This is also the case between the boundary tolerance of t
boundary,min
and t
boundary,max
as well as between
t
window,min
and t
window,max
. It is important to set up the trigger pulses accordingly to avoid violations in these areas.
Figure 7. Upper and Lower Boundary Visualization
TIMING RULES OF WINDOW-WATCHDOG
After the reset of the supervisor is released, the lower boundary of the first WDI window is disabled. However,
after the first WDI pulse low-to-high transition is detected, the lower boundary function of the window is enabled.
All further WDI pulses will need to fit into the configured window frame.
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