Tool/software:
LP8864 application circuit is as below, it is used as power supply for TFT panel backlight. When LP8864 EN pin is offered 3.3V, 948_VDD_BL_20.58V output 19.6V. But if PWM pin has 305Hz pwm signal input, the backlight of TFT panel will be turned on for a short time (about several milli-seconds) and turned off immediately, and I test the output voltage of 948_VDD_BL_20.58V is falling down. And when 948_VDD_BL_20.58V outputs 19.6V, the voltage of LP8864 SD pin is around 5V. But when LP8864 PWM pin has 305Hz pwm signal input, the voltage of LP8864 SD pin is around 12V which made Q600 turn off (see the test waveform in below for the details). I have some questions about LP8864:
1. Why LP8864 SD pin switchs to 12V which made Q600 turn off if there is 305Hz suqre wave input for PWM pin?
2. Please help to review the below circuit and give the feedback whether the below circuit has any issues?
3. if we want to turn on the backlight of TFT panel, what's the process need to do for LP8864 besides pull up EN pin as 3.3V?
As the project timing is very urgent, pls help to check and give the feedback ASAP.
Thanks a lot.
