TLE7469 Datasheet, PDF (17/21 Pages) Infineon Technologies AG – Dual Low Drop Voltage Regulator

TLE 7469
the closed window is interpreted as a pretrigger failure and results in a reset. After the
closed window the open window with the duration t_OW is started again. The open window
lasts at minimum until the trigger process has occurred, at maximum t_OW is 32 ms (typ.
value with fast timing).
A HIGH to LOW transition of the watchdog trigger signal on pin WDI is taken as a trigger.
To avoid wrong triggering due to parasitic glitches two HIGH samples followed by two
LOW samples (sample period t_sam typ. 0.25 ms) are decoded as a valid trigger (see
Figure 7). A reset is generated (RO goes LOW) if there is no trigger pulse during the
open window or if a pretrigger occurs during the closed window. The triggering is correct
also, if the first three samples (two HIGH one LOW) of the trigger pulse at pin WDI are
inside the closed window and only the fourth sample (the second LOW sample) is taken
in the open window.
Reset
Alw ays
Ignore
W indow
Trigger During
Closed W indow
No Trigger During
O pen W indow
A lw a y s
C lo s e d
W indow
Trigger
No Trigger
Figure 6 Window Watchdog State Diagram
Open
W indow
AEA03533.VSD
Final Data Sheet
17
Rev. 1.3, 2004-10-28