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BOOSTXL-DRV8323RS: SPI interface: Pull UP on SDO lines

Jagbir
Expert 1525 points
Part Number: BOOSTXL-DRV8323RS
Other Parts Discussed in Thread: DRV8323

Hi,

In the design files of BOOSTXL-DRV8323RS there is a pull up resistor(R12) valued  1.5KOhm on the SDO line. What's the rationale of such a 'strong' pull up.

Thanks

  • 0
    TI__Prodigy 620 points

    Hi Jagbir,

    Thanks for reaching out to the team.

    As a quick recap, SDO is pulled low during SPI communication. Thus a pull up resistor is used to maintain a logic high value during the "idle" state where no communication occurs. A strong pull up resistor makes sure that the line stays high by default which helps with EMI concerns. It also helps with swapping logic levels quickly, but it will increase current pulled from the supply.

    Overall, it is a strong pull up resistor but shouldn't have any impact on your testing. The design decision was made just to guarantee logic high during idle state. You are welcome to make the pull up weaker if you would like.

    Let me know if this helps!

    Tyler McCulloch

  • 0 in reply to Tyler McCulloch
    Expert 1525 points

    Thanks Tyler. My design doesn't need the internal buck regulator on DRV8323RSxxxx. As an alternative, I can use the part# DRV8323SRGZ ,which doesn't have an internal buck regulator but that part is not in stock on TI.com. Can I leave those 6 pins (47,48,44,45,1,43,46) disconnected on DRV8323RSxxxx.

  • 0 in reply to Jagbir
    TI__Prodigy 620 points

    Hi Jagbir,

    Let me discuss this with my team before giving you an answer. I want to make sure the setup I suggest will not cause any issues in the future. I will aim to get back to you by the end of the day Monday.

    Thanks!

    Tyler McCulloch

  • 0 in reply to Tyler McCulloch
    TI__Prodigy 620 points

    Hi Jagbir,

    The buck circuit is completely separate from the remaining DRV8323 circuitry; only GND is shared. If you are not going to use the buck, it is recommended to GND the input pins and nSHDN pin to make sure the buck stays off.

    Let me know if this resolves your issue!

    Tyler McCulloch