LP8861-Q1: NO output of LP8861-Q1

Betty Guo

Expert 7300 points

Part Number: LP8861-Q1

Hi team,

customer application as below:

input 12V

output 28V/80mA per channel, 4sLED

OVP is 43V

f of PWM is 10kHz

problem is that LCD display can't be light, measure the LP8861 output, it is 12V, and no SW signal. FAULT pin is high. measure FB pin the voltage is 1.9V(normal is 1.25V)

because the FAULT pin is high, we can't detect which fault condition is triggerd. could you help check this case? thanks.

below is scheamtic

over 3 years ago

0 Charles-Chen over 3 years ago

TI__Genius 11836 points

Hi Betty,

Can you provide the waveform of SW, Vout and fault?

Have you set the NTC circuit correctly?

0 Betty Guo over 3 years ago in reply to Charles-Chen

TI__Expert 7300 points

Hi Charles,

I will let customer provide the waveform.

since the Vout is equal with input, I think the boost is not work. what condition will cause boost stop work without fault?

thanks.

0 Betty Guo over 3 years ago in reply to Charles-Chen

TI__Expert 7300 points

Hi Charles,

SW no output waveform, only DC12V. they didn't use NTC circuit.

0 Charles-Chen over 3 years ago in reply to Betty Guo

TI__Genius 11836 points

Hi Betty,

Can this be reproduced in every board? You output capacitor is too small.

Please provide the start up waveform of SW, Vout, fault and EN.

0 Betty Guo over 3 years ago in reply to Charles-Chen

TI__Expert 7300 points

not on every board, but it can be reproduced.

for output capacitor, what's your recommendation? I will let customer capture the waveform. thanks.

0 Charles-Chen over 3 years ago in reply to Betty Guo

TI__Genius 11836 points

Hi Betty,

I have seen your email and let's close it through emails.

0 Charles-Chen over 3 years ago in reply to Charles-Chen

TI__Genius 11836 points

Hi Betty,

Please help close this thread.

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LP8861-Q1: NO output of LP8861-Q1