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DRV8885: Internal clock

NAOKI AOYAMA
Guru 11215 points
Part Number: DRV8885

Hello,

Our customer use the DRV8885, have a question.

The customer consider the EMI noise reduction.

Could you tell me how about the frequency of internal clock for the charge pump circuit and

the OCP digital counter?

Best Regards,

Naoki Aoyama

  • 0
    TI__Genius 14485 points
    Hi Aoyama-san,

    Let me ask our designers about this.

    The clock inside the DRV8885 is a spread spectrum clock, so it should help with EMI issues.

    Is your customer experiencing EMI issues in their system with this device, or are they trying to prevent EMI issues during the design phase?
  • 0 in reply to James Lockridge19
    Guru 11215 points
    Hello James-san,

    Thank you for your reply.
    It is useful information that the DRV8885 has a spread spectrum clock.
    The customer are trying to prevent EMI issues during the design phase.
    I will be waiting for your research.

    Regards,
    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Genius 14485 points
    Aoyama-san,

    Here is the feedback from our design team:

    1. Charge pump clock frequency is nominally 370 KHz.
    2. OCP timer is ~1.2ms

    We don't anticipate any EMI issues with this device, and we typically do not recommend adding any components outside of those listed in the datasheet. Following the layout guidelines should be sufficient.
  • 0 in reply to James Lockridge19
    Guru 11215 points
    Hello James-san,

    Thank you for your reply.

    Sorry, I gave you wrong answer.
    The customer already estimate EMI noise. There is poor margin at 200MHz.
    The condition of the customer as follows.
    VM=24V
    Full scale current = 700mA - 800mA
    Full Step and Mixed-decay.

    Could you tell me what is the source of EMI noise as 200MHz?

    Best Regards,
    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Genius 14485 points
    Hi Aoyama-san,

    Has the customer confirmed that the DRV8885 creates the noise, or are there other microcontrollers and switching regulators on the board that may create the noise?

    If it is the DRV8885, then it might be from the digital clock. Make sure the decoupling capacitor on DVDD is placed as close to the part as possible.
  • 0 in reply to James Lockridge19
    Guru 11215 points
    Hi James-san,

    I will check the situation of the customer and suggest to connect decoupling capacitor.

    Thanks,
    Naoki Aoyama