TPS61081 PWM dimming - timing limits?

Fraser Warne

Other Parts Discussed in Thread: TPS61081

We are using the TPS61081 to drive the backlight of a TFT display using the circuit shown on page 24 of the datasheet. We have noticed that the TPS61081 does not behave as expected with higher frequency PWM, and extremes of duty cycle (eg. 2% or 98%).

What are the limits on the timing of the PWM waveform?

What are the mimum on and off times for the FET?

over 11 years ago

0 Jasper Li over 11 years ago

TI__Mastermind 46905 points

hi Fraser

do you mean the circuit of figure 24? it is on the page 18. and you want to know the max. frequency of the "PWM signal"? thanks

best regards

Jasper li

0 Fraser Warne over 11 years ago in reply to Jasper Li

Intellectual 295 points

Hi Jasper,

Yes - that is the circuit I am refering to. Sorry confusing the figure number with the page number.

Best regards,

Fraser.

0 Jasper Li over 11 years ago in reply to Fraser Warne

TI__Mastermind 46905 points

hi Fraser

there is some delay time from the PWM signal to LED current. it causes by the respond time of the system, which is related to the control method of boost,the value of inductor and output capacitor. i think you can measure the PWM signal and Rset(1ohm) voltage signal using oscilloscope, and find the delay time.the delay time may confine the frequency of the PWM signal.

thanks

Jasper li

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TPS61081 PWM dimming - timing limits?