Tool/software:
Hi.
I'm currently working with the TPS922055 EVM board and noticed some unexpected behavior related to PWM dimming:
When I gradually increase the duty cycle as shown in the attached examples, the LED stays off up to a certain threshold. Then, all of a sudden, it turns on—not at its dimmest level, but at the brightness corresponding to that duty cycle. Once the LED is on, if I start decreasing the duty cycle, it dims as expected and finally turns off at 0% duty.
My question is:
Why doesn't the LED turn on immediately at lower duty cycles during the initial ramp-up? Why does it seem to "jump" to a higher brightness instead of gradually increasing from very dim?
Additionally, I have another issue with my custom board using the TPS922055:
Unlike the EVM, my board does not allow smooth dimming. For example, on the EVM I can clearly observe the brightness difference between duty cycles of 2% and 1%. On my custom board, however, after I go below around 2.4%, the LED dims only once, and further changes to lower duty cycles do not affect the brightness—it remains constant.
What could be causing this limited dimming response on my custom board?
Any insight or suggestions would be greatly appreciated. Thanks in advance!
