
L99PM62XP
Description
Doc ID 16363 Rev 2
watchdog starts with a long open window. After serving the watchdog, the C may send the
device back to V1 standby mode.
After power-on or standby mode, the watchdog is started with a long open window (65 ms
nominal). The long open window allows the micro controller to run its own setup and then to
trigger the watchdog via the SPI. The trigger is processed when the CSN input becomes
HIGH after the transmission of the SPI word.
Writing ‘1’ to the watchdog trigger bit terminates the long open window and start the window
watchdog (the timing is programmable by SPI). Subsequently, the micro controller has to
serve the watchdog by alternating the watchdog trigger bit within the safe trigger area (refer
to
Figure 27). A correct watchdog trigger signal is immediately start the next cycle.
After 8 watchdog failures in sequence, the V1 regulator is switched off for 200ms. If
subsequently, 7 additional watchdog failures occur, the V1 regulator is completely turned off
and the device goes into VBAT standby mode until a wakeup occurs.
In case of a watchdog failure, the outputs (RELx, OUTx, V2) are switched off and the device
enters fail-safe mode (i. e. all control registers are set to default values except the ‘OUT3
control bit’).
The following diagrams illustrate the watchdog behavior of the L99PM62. The diagrams are
split into 3 parts. First diagram shows the functional behavior of the watchdog without any
error. The second diagram covers the behavior covering all the error conditions, which can
affect the watchdog behavior. Third diagram shows the transition in and out of Flash mode.
All 3 diagrams can be overlapped to get all the possible state transitions under all
circumstances. For a better readability, they were split in normal operating, operating with
errors and Flash mode.
Figure 9.
Watchdog in normal operating mode (no errors)
WD
OFF
long
open
window
Window
Mode
propper trigger in
Window mode
TRIG = 1'
go Standby
V1 > Vrstthr
VBAT Standby
V1 Standby (I(V1) < ICMP)
Active mode