Data Sheet
110
Rev. 1.00
2017-07-31
TLE9262BQXV33
Supervision Functions
15.2.2
Window Watchdog
Compared to the time-out watchdog the characteristic of the window watchdog is that the watchdog timer
period is divided between an closed and an open window. The watchdog must be triggered within the open
window.
A correct watchdog trigger results in starting the window watchdog period by a closed window followed by an
open window.
The watchdog timer period is at the same time the typical trigger time and defines the middle of the open
window. Taking the oscillator tolerances into account leads to a safe trigger area of:
t
WD
x 0.72 < safe trigger area < t
WD
x 1.20.
The typical closed window is defined to a width of 60% of the selected window watchdog timer period. Taking
the tolerances of the internal oscillator into account leads to the timings as defined in
Figure 49
.
A correct watchdog service immediately results in starting the next closed window.
Should the trigger signal meet the closed window or should the watchdog timer period elapse, then a
watchdog reset is created by setting the reset output RO low and the SBC switches to SBC Restart or SBC Fail-
Safe Mode.
Figure 49 Window Watchdog Definition
closed window
open window
t /
[t
WD _TIMER
]
safe trigger area
t
WD
x 0.72
t
WD
x 1.20
uncertainty
uncertainty
t
WD
x 0.48
t
WD
x 1.80
Watchdog Timer Period (WD_TIMER)
Typ. closed window
Typ. open window
t
WD
x 0.6
t
WD
x 1.0
t
WD
x 0.9
