I have an LDO (TPS7A4101) which has two 10 uF, 50 V ceramic capacitors on the input. The LDO is generating 3.3 V, which is used by MCU to drive the LEDs.
When the system goes into standby mode, the LEDs turn on for 1 sec and stay off for 8 sec. During that time, the capacitors make a buzzing sound which is at 4kHz. The LEDs are driven by the MCU using PWM signal, which is running at 4kHz.
I tried using film capacitors which are too big for the PCB, but that stops the sounds for sure. I also tried different values of capacitors such as 4.7 uF, 50 V and 35 V versions, but the noise remains the same.
Does anyone know how this can be fixed in hardware?
In software I know that if, instead of PWM signal, I use high and low signal then it works, but I am looking for a hardware solution.