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TAS6424E-Q1: TAS6424 can not detect "short to power" fault

mingzhi Sun
Prodigy 10 points

Part Number: TAS6424E-Q1

While testing the fault diagnostics function of the TAS6424, I encountered an issue where a short-to-battery fault cannot be detected. The specific test conditions are as follows:

  1. Preconditions: VBAT = 12.5 V, PVDD = 24.5 V, channels 1 through 4 are normally connected to 4-ohm loads.
    Test procedure: After power-up, switch all channels to Play mode and continuously read registers 0x0C and 0x0D; no fault is indicated. Then short any output pin of channel 4 to BAT and continuously read registers 0x0C and 0x0D; no fault is indicated.

  2. Preconditions: VBAT = 12.5 V, PVDD = 24.5 V, channels 1 through 4 are normally connected to 4-ohm loads, and any output pin of channel 4 is shorted to BAT.
    Test procedure: After power-up, switch all channels to Play mode and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4. Then remove the shorting wire from channel 4 and continuously read registers 0x0C and 0x0D; no fault is indicated. Then reconnect the shorting wire to channel 4 and continuously read registers 0x0C and 0x0D; no fault is indicated.

  3. Preconditions: VBAT = 14.5 V, PVDD = 24.5 V, channels 1 through 4 are normally connected to 4-ohm loads, and any output pin of channel 4 is shorted to BAT.
    Test procedure: After power-up, switch all channels to Play mode and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4. Then remove the shorting wire from channel 4 and continuously read registers 0x0C and 0x0D; no fault is indicated. Then reconnect the shorting wire to channel 4 and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4.

  4. Preconditions: VBAT = 14.5 V, PVDD = 14.5 V, channels 1 through 4 are normally connected to 4-ohm loads, and any output pin of channel 4 is shorted to BAT.
    Test procedure: After power-up, switch all channels to Play mode and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4. Then remove the shorting wire from channel 4 and continuously read registers 0x0C and 0x0D; no fault is indicated. Then reconnect the shorting wire to channel 4 and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4.

My question is: why does the short-to-battery fault detection vary with different VBAT voltages? 

  • 0
    Prodigy 10 points

    1. additional test

      Preconditions: VBAT = 12.5 V, PVDD = 12.5 V, channels 1 through 4 are normally connected to 4-ohm loads, and any output pin of channel 4 is shorted to BAT.
      Test procedure: After power-up, switch all channels to Play mode and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4. Then remove the shorting wire from channel 4 and continuously read registers 0x0C and 0x0D; no fault is indicated. Then reconnect the shorting wire to channel 4 and continuously read registers 0x0C and 0x0D; a short-to-battery fault is indicated on channel 4.

  • 0 回复 mingzhi Sun
    TI__Mastermind 49560 points

    Because the TAS6424's runtime detection threshold is a fixed percentage (~60%) of PVDD, not an absolute voltage or a function of (PVDD - VBAT).