TPS92830-Q1: Output LED flicker at low PWM duty cycle

Angus Thomson1

Part Number: TPS92830-Q1
Other Parts Discussed in Thread: TPS92830EVM, TPS92613-Q1

I am using the TPS92830-Q1 to drive 3 high power LEDs with an external PWM source, and am currently using the evaluation board to test it (TPS92830EVM). However when driving any of the PWM inputs with a low duty cycle (of around 15%) the LED flickers noticeably.

I have examined the jitter on the input PWM waveform and this looks fine at about 250ns, but on the output is around 14us of jitter; see waveforms below:

PWM input jitter:

Output jitter (at the LED output of the driver):

Both waveforms:

What we need is to run the LEDs at low duty cycles with no visible flicker - can you provide some input as to why this might be happening?

over 3 years ago

0 Frank Qiu over 3 years ago

TI__Genius 15776 points

Our device can't support short period on time, so if you want to use it in low duty cycle, please increase the frequency.

0 Angus Thomson1 over 3 years ago in reply to Frank Qiu

Prodigy 60 points

Thanks for the response, though could you please clarify what the minimum PWM on time should be? Also when you say 'increase the frequency' do you mean increase the period? Increasing the frequency would lead to a shorter on time for the same duty cycle!

0 Frank Qiu over 3 years ago in reply to Angus Thomson1

TI__Genius 15776 points

Sorryt, I mean decrease. You can test the minimum on time by yourself.

0 Angus Thomson1 over 3 years ago in reply to Frank Qiu

Prodigy 60 points

Ok, thanks. Do any of TI's single LED drivers (e.g. TPS92613-Q1 or TPS92610QPWPRQ1) have the same limitation?

0 Frank Qiu over 3 years ago in reply to Angus Thomson1

TI__Genius 15776 points

Hi the minimum on time of tps9261x is about 10us. whether it can satisfy your need?

Power management

Power management forum

TPS92830-Q1: Output LED flicker at low PWM duty cycle