ZHCSTD7A December 2021 – November 2023 BQ79631-Q1
PRODUCTION DATA
The oscillators are monitored by watchdog circuits. There are two oscillators in the device, the HFO and the LFO. If these oscillators are not functioning, the device does not operate. If the HFO or LFO does not transition within the expected time, the watchdog circuits causes a digital reset.
When this unexpected reset occurs, it is recommended that the host sends a SHUTDOWN ping/tone to the problem device and then send a WAKE ping to reset the daisy-chain. If the oscillators are truly damaged, the device will not restart and must be replaced.
In addition to the watchdog, the LFO frequency is monitored to ensure it stays within acceptable limits. If the LFO frequency falls outside of the expected range, the FAULT_SYS_FAULT[LFO] bit is set.