In using the TPS28225, we have discovered a couple of behaviors that we were not able to identify in the datasheet.
1. The part outputs do not toggle at low PWM input rates. What is the minimum PWM frequency required to operate this part? We also noticed that it does not operate well at certain duty cycles. What are the minimum and maximum pulse widths required?
2. The part does not work at all if we do not have the PWM running and then pulse the enable signal. Is this expected behavior? Our initial system just had the enable pulled high with a 20K resistor. Then after our microprocessor booted and started running the PWM, we found that we had to transition EN low and then high to get the outputs working. In the example circuits, the enable signal is often just connected to VDD. I'm not sure why we are seeing this behavior. Our controller does not use the 3-state mode and we tried tying a 3.5K ohm resistor between PWM and ground to disable the 3-state mode.
Any light you can shed on these subjects would be appreciated!
Jon
