Texas Instruments TPS3809, Руководство пользователя

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10 SPRUI96 – October 2016
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If the device does not detect a rising edge at the WDI pin, it will reset delay approximately 25 ms and
return back to normal operation. This behavior is shown in
Figure 15 and Figure 16 .
Figure 15. TPS3813K33-Q1 Figure 16. TPS3813I50-Q1
The watchdog window settings can be calculated and verified using the Window Watchdog Calculator and
Visualizer tool as seen in Figure 17 . Therefore, by using the jumpers as outlined above in Table 6 the
WDT pin is tied to ground through a 3300-pF capacitor. The former results in a watchdog window with
limits of t
boundary,max
= 35 ms and t
window, min
= 895.3 ms. Once the window has been configured, the watchdog
timer should re-trigger to use the Watchdog Timer Input (WDI) pin with an external signal that fits within
the watchdog window to avoid a timeout and RESETN pin is asserted. Care must be taken to avoid a
boundary violation, which results from a trigger pulse in the lower or upper boundary of the watchdog
window. Figure 17 shows a boundary violation that causes the RESETN pin to pull low. The WDI pulse
seen at the falling edge of RESETN triggers at the lower boundary. Therefore, the user must adjust the
pulse signal properly.
Figure 17. Watchdog Window Boundary Violation TPS3813K33-Q1
Revision History
DATE REVISION NOTES
November 2016 * Initial Release