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TPS92513: Frequency range of PDIM causes the stripes in camera‘s image

Lucas huang
Prodigy 10 points
Part Number: TPS92513
Other Parts Discussed in Thread: LM3409, TPS92515

We found that the frequency of PDIM signal need to higher than 10khz to avoid the stripes . 20Khz will be better.

So i decide to use the ADJ pin to adjust the current instead of PDIM. I plan to connect the ADJ pin to MCU's DAC pin  and use the PDIM as a ENABLE/DISABLE singal. Is there any risks to this solution?

Application scenarios:  Two green led in series,  1A current, 3~4V each led.   adjustable to the lightness.

Or could you help me to introduce another suitable  driver IC to me?

  • 0
    TI__Mastermind 28655 points
    Hello,

    That should be okay:

    Just be aware: The TPS92513 uses a sample-and-hold switch on the error amplifier output. During the PDIM off-time the COMP
    voltage remains unchanged. Also, the error amplifier output is internally clamped low. These techniques help the
    system recover to its regulation duty cycle quickly. The dimming frequency range is 100 Hz to 1 kHz and the
    minimum duty cycle is only limited in cases where the BOOT capacitor can discharge below its under-voltage
    threshold of 2 V (VIN is within 2 V of the total output voltage).

    Which means if PDIM is low long enough the boot capacitor will discharge.

    Best Regards,
  • 0 in reply to Irwin Nederbragt
    TI__Mastermind 28655 points
    Hello,

    Try looking at the TPS92515 or LM3409. They are hysteretic parts. LM3409 does not have the boot capacitor discharge issue.

    Best Regards,