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TPS61161: PWM Frequency renge in the external PWM circuit

Part Number: TPS61161

Dear Specialists,

My customer is considering TPS61161 and has aquestion.

Could you please advise?

---qiestion

According to the datasheet of 7.4.2 PWM Brightness Dimming, by using external PWM circuit, it can use for lower frequency than 5kHz.

The schematic is P.22

In this case, How is the lowest frequency?

For instance, Could it be used for 100Hz?

Is there any limitation?

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • Hi Shinichi,
    The limitation would be the output voltage ripple. As shown in the datasheet, the PWM signal is filtered before goes into FB pin of the IC. The voltage on FB will regulate output current. To get low ripple current, the votlage of FB should be flat. If there is low frequency ripple on Vfb, the output voltage on output capacitor will have that too and 100HZ could cause audible noise.
  • Hi Catyss

    Thank you for your reply.

    The external PWM it should be flat on the FB pin.

    I'll share your information with the customer.

    I appreciate your great help.

    Best regards,

    Shinichi