TPS92692-Q1: PWM?

kevin.huang_FJXM

Part Number: TPS92692-Q1

At present, our logo light scheme adopts tps92692-q1, driving 14 LEDs (current 150mA, voltage 3.2V), external PWM input to adjust brightness.

TA = 25°C, VIN = 12V, VIADJ = 1.59 V, Cvcc = 2.2μF, Ccomp = 10pF, Rcs = 300 mΩ, Rt = 20 kΩ,Vpwm = 5 V ,60HZ,

The problems encountered are:

After inputting VPWM = 5 V, 14 LEDs will flash after 60Hz. After adjusting PWM pulse width, what changes is led flicker frequency!!! What we need is that the LED is always on, adjust the brightness through PWM!!!

Please provide technical solutions, thank you!

over 5 years ago

0 Tuan Tran74 over 5 years ago

TI__Mastermind 18890 points

Hi Kevin,

Your schematic shows that Ccomp is a total of 0.1uF (C35) and 3300pF (C34). Your comment above you mention that Ccomp is 10pF. Which one is correct? 10pF is way too small. I would use the 0.1uF for Ccomp to begin with.

If there are still issues then I would need scope captures of what you are seeing in order for me to help.

Thanks Tuan

0 kevin.huang_FJXM over 5 years ago in reply to Tuan Tran74

Expert 2925 points

Tuan:C34 and C35 are useful at the same time.

0 Tuan Tran74 over 5 years ago in reply to kevin.huang_FJXM

TI__Mastermind 18890 points

Hi Kevin,

When you said Ccomp is 10pF what do you mean by that in your original post? I would still need scope capture of what is going on with the LED current, COMP, inductor current and switch node to figure out what is going on.

Thanks Tuan

0 kevin.huang_FJXM over 5 years ago in reply to Tuan Tran74

Expert 2925 points

The customer found the problem

PIN 20.

0 Tuan Tran74 over 5 years ago in reply to kevin.huang_FJXM

TI__Mastermind 18890 points

Hi Kevin,

I am glad you have resolve the issue.

Thanks Tuan

0 kevin.huang_FJXM over 5 years ago in reply to Tuan Tran74

Expert 2925 points

resolve the issue

Power management

Power management forum

TPS92692-Q1: PWM?