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Original question:

UCC5880-Q1: ADC fault

UCC5880-Q1: SPI fault and faster Switching

Yassine Damoh
Prodigy 180 points
Part Number: UCC5880-Q1

Tool/software:

Hello,

When using fast switching, we're frequently seeing SPI fault along with other faults. I'm assuming this fault could be cause by high frequency ringing coupled from the power board. is that a fair assumption ?

With slower switching, we are only observing the SPI fault in some conditions ( higher DC bus voltage).

is this a known issue with early silicons ? is there's a recommended approach to avoid this fault while keeping the fast switching rates (HW filtering or SW configuration)?

Thanks,
Yassine

  • 0
    TI__Expert 5811 points

    Hi Yassine,

    Thanks for reaching out! 

    The detection mechanisms for the SPI fault are:

    1. While nCS is low the number of clock pulses is not a multiple of 16. This is the most common cause, as any noise coupling to the nCS pin when there is not SPI communication, or the nCS pin and CLK pin while there is active SPI communication will cause this fault. The recommended resolution is to add or increase RC filtering on the SPI input pins. This does typically come from coupled noise to the spi inputs, but can also be a logic error form the MCU.

    2. The wrong SPI CRC is written to the CRC register (Address = 0x11). This is only possible during Config mode.

    3. An SPI frame that does not match any valid command is received. This would be an MCU logic error.

     The only change relevant to SPI is that the pullup pin on nCS was a pulldown on early prototypes, which could cause an SPI fault if nCS from the MCU went HiZ for a time.

     

    What sort of filters do you have on the SPI inputs? This is where I would focus debug.

    Regards,

    Daniel

  • 0 in reply to Daniel Norwood
    Prodigy 80 points

    Daniel,

    This was early Silicon (Yassine's on leave).


    We will apply ferrite filters at each end of the signal lines.

    Can you direct me to an errata note on the early silicon. We just received (a few) production parts through GL but I don't want to fine we have issues if the pullup became a pulldown etc.

    Regards,

    John

  • 0 in reply to John Martin4
    TI__Expert 3735 points

    Hi John,

    The errata document can be found in the MySecure Folder.

    Regards,

    Akshat

  • 0 in reply to John Martin4
    TI__Expert 5811 points

    Hi John,

    I will send you the errata over email