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PGA411-Q1: Problem with boost power supply

Alexandre Boyer
Prodigy 40 points
Part Number: PGA411-Q1

Hello,

I develop a board with PGA411 and a microcontroller software to read angle and speed. The software was validated with PGA411_EVM.

I test my board: power supplies provided to PGA411 are correct (5 V), SPI communication works correctly and COMAFE is equal to 2.5 V. However, the boost power supply does not start. The voltage Vext remains at 5 V.

I use the factory configuration. The fault pin is high and diagnosis indicates an Exciter Overvoltage Fault (bit EXTOV set to '1' in DEV_STAT1).

Could you help me to understand and correct this problem ?

Thank you in advance.

Alexandre Boyer

  • 0
    TI__Mastermind 23810 points
    Alexandre,

    I recommend checking the following waveforms during your start-up sequence and up until the fault pin is flagged.

    VCCSW
    VSW
    VEXT
    OE1
    OE2

    Also, what do you have EXTUVT set to? If it is not at the maximum, you should try increasing it to 111b.
  • 0 in reply to Clancy Soehren
    Prodigy 40 points
    Dear Clancy,

    thank you very much for your answer. I check VCCSW, VSW and VEXT waveform during start-up. They are stucked at 5 V directly and OEx remain constant. I don't see any switching on VSW.
    I use the facotry settings so EXTUVT is set at the maximum.

    Alexandre
  • 0 in reply to Alexandre Boyer
    Prodigy 40 points
    Dear Clancy,

    I try to provide an external Vext without the boost. I depopulated the external components of the boost and set MODEVEXT to the external voltage reference I applied (10 V). I set the external mode in 4Vpp and the gain of the external amplifier to the minimum value.
    The differential excitation outputs remain at 0 V and the fault pin is flagged. SPI diagnosis still indicates an Exciter Overvoltage Fault (bit EXTOV set to '1' in DEV_STAT1). I also sensed the voltage on ORS pin (I activated it by setting XEXT_AMP to 1). I measured 5 V.
    I verified all the connection, all the power supplies. Everything seem correct.
    Do you have any suggestions to help me to solve this problem ?

    Alexandre
  • 0 in reply to Alexandre Boyer
    TI__Mastermind 23810 points
    Alex,

    Do you know the current consumption of the PGA411 in this state?

    Also, does pulling FAULTRES low allow the part to start (you should see switching on VSW, VEXT should rise up to the programmed value, and there should be a 10kHz signal on the OEx pins)?

    Thanks,

    -Clancy
  • 0 in reply to Clancy Soehren
    Prodigy 40 points

    The current consumption I observed is about 30 mA. I tried to pull FaultRes low but the the chip returns directly in fault state. I observed no transient behaviour on VSW and VEXT, and no 10 kHz sine waveform on OEx pins.

    Alexandre

  • 0 in reply to Alexandre Boyer
    TI__Mastermind 23810 points
    Does the PGA411 start working while FAULTRES is low? If you pull it low and then high again, it will go back to the fault state if a fault is detected.

    It might be helpful if you send me your schematic through private message.