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TPS65217: Issue with AM3358BZCZA100 and TPS65217C

Sergii Makovetskyi
Intellectual 495 points
Part Number: TPS65217
Hi Support team,
Could you please support us with some questions to design we made with AM3358BZCZA100 and TPS65217C PMIC.
We are facing some issues related to PMIC we think:
  1. VLDO1 of PMIC TPS65217C pin 3 voltage from time-to-time jumpes from 1.8V to 2V. The voltage is an output of an LDO, so we assume there should be stable 1.8V. What could be a root cause of the voltage jumping?
  2. When power to PMIC is switched off and on again in a short period of time, the board cannot start from time to time. Usual current consumption of board is 0.3-0.4 A, but if the issue occurs, the current consumption is 0.1-0.2 A and board is not running. PMIC outputs incorrect voltages, as a result, the CPU cannot start. Any manipulations with the PMIC (as reset pin, enable pin) could not restart the PMIC to normal operation. What could be a root cause of PMIC improper startup

Please also find attached schematic diagram of our design.

  • 0
    TI__Mastermind 30280 points
    1) Does this happen during (a) the power-on sequence, (b) during normal operation after all rails are in regulation and PGOOD is high, or (c) during the Power-down sequence? An LDO voltage running-off is using an indication of a leakage path from one rail to another during power-on/power-down due to irregular sequencing

    2) this can happen if there is no battery in the system but the BAT pin is floating. The BAT voltage is held high by a large distributed bulk capacitance on the SYS pin. If AC is removed for <1s and the voltage on AC & BAT is non-zero, the next AC low-to-high Wakeup event can be missed while the TPS65217 is running the 1s Fault timer. The digital has power and it is actually looking for one of these voltages to reach 0V to be considered "low".

    Try connecting a light load (1k-10k) from BAT to GND at TP12 on your schematic.

    It is also wise to change UVLO to 2.73V (00b in Reg. 0x18, bits [1:0]) instead during the initialization sequence of the PMIC. The default is 3.3V and the issue will only occur if the AC voltage drops below UVLO for <1s before returning to 5V

    If the issue persists, it is possible to prevent this entirely with an external supervisor and load switch between the power supply and the AC pin.