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[TPS61183] Recommended frequency & duty ratio of Direct PWM mode at dimming

Chang-woo YANG
Expert 1285 points
Other Parts Discussed in Thread: TPS61183

Hello~

I have some questions for TPS61183...

Please refer to below schematic...

I'm using Direct PWM Dimming Method, and Direct PWM frequency is 24KHz...  I'm also setting up to 40nS for minimum on-time duty, and maximum duty ratio is 100% (always high input to PWM_IN pin).

1. According to datasheet, the range of FPWM_O (IFBx PWM dimming frequency - direct PWM mode) is 0.1 ~ 50 KHz.  But the range of FPWM_I (PWM input signal frequency) is 0.1 ~ 22 KHz.  Maximum value is different...  Can I use 24KHz as input frequency for Direct PWM frequency...?

2. I'm using 1.5K serial resistor for PWM_IN input pin...  Does this get into trouble about Direct PWM Dimming...?

3. Do you have recommended value of PWM dimming frequency for direct PWM mode...?

4. Does TPS61183 need the minimum on-time value at direct PWM mode...?  (For example, 0.5%, 10nS, etc...)

5. If TPS61183 need the minimum on-time for PWM dimming, when I'm inputting the lower value than minimum on-time, does it have problem for TPS61183...?

6. Do you have calulation formula of dimming ratio at any specified input dimming frequency...?  I need the dimming ratio at 24KHz Direct PWM frequency...

Thanks... C.W. :)