ZHCSI09S June 2010 – August 2018 TPS65911
The device includes a backup battery switch connecting the VRTC regulator input to a primary battery (VCC7) or to a backup battery (VBACKUP), depending on the voltage value of the battery.
The VRTC supply can then be maintained during a BACKUP state as long as the input voltage is high enough (> VBNPR threshold). Below the VBNPR voltage threshold, the digital core of the device is set under reset by internal signal Power-on Reset (POR).
The backup domain functions which are always supplied from VRTC are:
The backup battery can be charged from the primary battery through an embedded charger. The backup battery charge voltage and enable is controlled through BBCH_REG register programming. This register content is maintained during the device BACKUP state.
Hence, when enabled, the backup battery charge is maintained as long as the primary battery voltage is higher than the VMBLO threshold and the backup battery voltage.