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TPS65910AA1 Not Working

Cary Davis
Prodigy 115 points

I have a new design in using a TPS65910AA1 and Sitara AM335X. 

So far, the TPS65910AA1 does not fully come on. VRTC nicely ramps up with 1.8V. The 32 kHz oscillator looks fine. If a backup battery is connected it continues to run the oscillator. However, no additional rails come up. I am using the TPS65910AA1 is a failry dumb mode and not using it's power on/off, button or other features. I simply want the device to power and sequence up the AM335X when external power is applied. I am using boot 0b10 mode ( EEPROM ).

I am concerned I am in a "chicken and egg" scenario since the TPS65910AA1 supplies its own power to VDDIO and I have not had anyone confirm where the sequence state machine's power comes from, if it's from VDDIO or internal VRTC. I have looked through the SWCA139A TPS65910AA1 checklist and found no major discrepancies. I did miss connecting pin 30, VFB3 to ground, but I am not using SW3 related circuitry. I am concerned about the use of PWRHOLD, SLEEP and PWRON since I have no use for them but SWCA139A says I can leave them floating if not used.

I appreciate anyone's help.

- Cary

  • 0
    Prodigy 115 points

    I got the circuit to work by connecting PWRHOLD ( pin 1 ) to VRTC. The original circuit had PWRHOLD tied high through to another rail, on VDIG1 which powers the digital section. As stated earlier,  SWCA139A indicates a recommendation of tying PWRHOLD to VRTC if control is not required, but under the "Not Used Features" it says it can be left floating since there is and internal pulldown. Regardless, I can only get the TPS65910AA1 to fully sequence and power up when PWRHOLD was connected to VRTC.


    - Cary