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TPIC8101: Schematic review

Ramkumar Ramasamy
Prodigy 10 points

Part Number: TPIC8101

Hi Team,

I would like to review this knock sensor schematic,
image.png

Could you please let me know whether I need to connect Pin #4 (OUT) to the MCU ADC pin? What is the exact use case of this signal? If it is not connected, what would be the impact or possible issue?

Also, could you please check the XIN and XOUT crystal connections? I would like to confirm whether the crystal connection is correct or if any additional connection to the MCU timing/clock pins is required.

Thanks.

  • 0
    TI__Intellectual 2060 points

    Hi Ramkumar,

    1. OUT Pin (Pin #4):
    Yes, connect it to your MCU ADC with a 2.2 nF capacitor to ground (required for stability). This gives you the analog integrated knock signal. Alternatively, you can read the same data digitally via SPI—but the 2.2 nF capacitor must still be connected.

    2. XIN/XOUT Crystal:
    Your circuit is correct. The TPIC8101 accepts an external clock (4-24 MHz) from your MCU, a crystal, or resonator. No additional MCU clock connections needed, only your SPI signals (CS, SCLK, SDI, SDO) and INT/HOLD.

    If you have any other questions please let me know.

    Best regards,
    Chase Girard

  • 0 in reply to Chase Girard
    Prodigy 10 points

    Hi chase,

    Thanks for the review.

    Regarding point 2:

    Based on your statement, I understand that I can remove the crystal if I use SPI mode instead of ADC. Is that correct?

    Thanks,

    Ram.

  • 0 in reply to Ramkumar Ramasamy
    TI__Intellectual 2060 points

    Hi Ram,

    You cannot remove the clock entirely, but you have flexibility in the source. The TPIC8101 requires a clock signal on XIN (4–24 MHz). However, the datasheet explicitly states you can provide this clock three ways,

    1. External crystal (your current circuit with C1, C2 load capacitors)
    2. Ceramic resonator (similar to crystal, with load capacitors)
    3. MCU clock output (direct signal to XIN—no capacitors needed)

    The clock requirement is independent of whether you use SPI or ADC mode—both need the clock running.

    I hope this clears up any confusion. If you have any other questions I would be happy to help.

    Best regards,
    Chase Girard