SLVS331I December 2000 – October 2021
PRODUCTION DATA
There are two ways to configure the watchdog timer window the most flexible is to connect a capacitor to WDT to set the upper boundary of the window watchdog while connecting WDR to either VDD or GND, thus setting the lower boundary. The other way to configure the timing is by wiring the WDT and WDR pin to either VDD or GND. By hardwiring the pins to either VDD or GND there are four different timings available; these settings are listed in Table 8-2.
SELECTED OPERATION MODE | WINDOW FRAME | LOWER WINDOW FRAME | |
---|---|---|---|
WDT = 0 V | WDR = 0 V | Max = 0.3 s | Max = 9.46 ms |
Typ = 0.25 s | Typ = 7.86 ms | ||
Min = 0.2 s | Min = 6.27 ms | ||
WDR = VDD | Max = 0.3 s | Max = 2.43 ms | |
Typ = 0.25 s | Typ = 2 ms | ||
Min = 0.2 s | Min = 1.58 ms | ||
WDT = VDD | WDR = 0 V | Max = 3 s | Max = 93.8 ms |
Typ = 2.5 s | Typ = 78.2 ms | ||
Min = 2 s | Min = 62.5 ms | ||
WDR = VDD | Max = 3 s | Max = 23.5 ms | |
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 tboundary,max and twindow,min. Within these values, the watchdog timer must be retriggered to avoid a time-out 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 8-2, it cannot be predicted if the device detects a violation or not and release a reset. This is also the case between the boundary tolerance of tboundary,min and tboundary,max as well as between twindow,min and twindow,max. It is important to set up the trigger pulses accordingly to avoid violations in these areas.