MP3398A is turning off for no apparent reason

Lighting Solutions
1

Hi,

We are using a MP3398A to drive a 2 strings backlight. For some reason, with PWM higher than 20%, the VOUT is rising up to OVP and the IC shutdown after a few ms. He can see the LED turn on and then off quickly.

At the moment where the VOUT rise, The LED voltage starts to rise.

All signal point behavior are perfectly normal.

Changing the frequency seem to change the behavior.

Any idea?

Failure_with Gate
Failure_with Gate1920×1081 183 KB

CH1 (Yellow) = MOSFET GATE

CH2 (Blue) = Dimming PWM

CH3 (Purple) = Vout

CH4 (Green) = VLED1

2

Hello, apologies for the delayed response.

Do you have a schematic to share here? And when you say 20%, you are referring to the duty cycle of your PWM signal correct? What is the frequency that you are using? Input and output voltages and currents on this system would be good to know too.

Also, I’m aware it has been some time since initial posting. If there have been updates here, please let me know.

Best,

Krishan