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TPS61196: the releationship of the PWM duty and frequency

user6494490
Prodigy 20 points
Part Number: TPS61196

I have some questions about the releationship of the PWM duty and frequency。

The Spec recommended minimum on time of the LED stringis 10μsec。 So what is the minimum value of the tpwh。

for example,if the PWM  frequency is 9.7kHz, can the duty be up to the 5% which without regards to LED strings on time。

  • 0
    TI__Genius 13001 points

    Hi,

    No matter what PWM frequency is, just as the datasheet says, the minimum on-time should be longer than 10us.

    If applying 9.7kHz PWM, the minimum duty cycle is 10us/(1/9.7kHz)=9.7%.

    Robin

  • 0 in reply to Yuting Shao
    Prodigy 20 points

    Hi :

    as the datashheet says(page 16),the PWM duty cycle can be from0% to 100%,

    so when the frequency is 90Hz, how to  reach the 0% duty cycle.

    and on the page8 ,figure 2,the low diming duty cycle is lower than 1% at 1KHz.

    besides,I measured the duty cycle at 9.7kHz,the cycle can lower than 5% actually。

    so whether it had risk when the cycle is lower than 9.7% when the frequency is 9.7Khz。

    and what is the failure  phenomenon 。

    thank you。

  • 0 in reply to user6494490
    TI__Genius 13001 points

    Hi,

    There is no doubt that you have read this datasheet carefully!

    Yes, the device can achieve even smaller duty cycle PWM dimming. But, if you apply duty cycle below recommended value, the actual current regulation can't be guaranteed. 

    Robin