TPS61194-Q1: LED Driver IC Fault issue

Chandan Kumar2

Part Number: TPS61194-Q1

HI TI Team

I am using TPS61194-Q1 for one of our application for LCD Backlight. when Enable signal is High (3.3V), and PWM Signal is Low (0V), we are getting constant output voltage as 27V with reference to input supply ground as per the Feedback path configuration, Input voltage is 12V. But when Enable signal is High (3.3V), and PWM Signal is High (3.3V), the IC is giving as a fault and output voltage is droping to 12V with reference to Input Supply ground and there is no voltage with reference to OUT1/OUT2/OUT3/OUT4.

we are connecting resistor as a load between VBoost and OUT1/OUT2/OUT3/OUT4 for Load Testing instaed of LCD Display for testing the card.

Please find the schematic for your reference.

Kindly suggest what could be issue for Fault and how to overcome the issue. Kindly let me know if there is mistake in providing the input to the IC.

over 6 years ago

0 Shirley He over 6 years ago

TI__Expert 5475 points

Hi,

I have some questions with regards to the schematic. Did you connect the four channel outputs together? What is the resistor value connected at each channel output?

0 Chandan Kumar2 over 6 years ago in reply to Shirley He

Prodigy 170 points

Currently all the resistors (R24, R25, R26 & R27) are kept as DNP for OUT1/OUT2/OUT3/OUT4 and we are connecting Load on each channel. so we are not connecting all the four channels output together. The load value id 220R on each channel. and VBoost voltage is set to 27V.

Can we give constant voltage to Enable and PWM for enabling and Brightness or we need to give PWM Pulse only for testing?

0 Shirley He over 6 years ago in reply to Chandan Kumar2

TI__Expert 5475 points

Hi,

There's no issue to give constant voltage to EN and PWM.

Regarding the issue you met, did you connect the output resistors before enabling the device or after EN and PWM are high? Do you have any waveforms showing the behavior when PWM is activated, including signals of Vout, FB, SW, Iout? Thank you.

0 Chandan Kumar2 over 6 years ago in reply to Shirley He

Prodigy 170 points

In have connected the output resistors before switching on the device and after that we are enabling the device and giving PWM logic voltage as high.

I will provide the waveform shortly to have better understanding of the IC Behavior.

0 Charles-Chen over 6 years ago in reply to Chandan Kumar2

TI__Genius 11836 points

Hi, Chandan,

Waveforms of Vout, FB, SW and Iout when PWM is activated are helpful for analyzing and solving problems.

0 Charles-Chen over 6 years ago in reply to Charles-Chen

TI__Genius 11836 points

Hi, Chandan,

I'll close this thread due to inactivity and if you have more questions please reply to it directly and it will open again.

Power management

Power management forum

TPS61194-Q1: LED Driver IC Fault issue