Tool/software:
Hello everyone,
I'm encountering an issue with the TPS2121 when using my custom PCB as a load. The setup works perfectly when the load is just a simple resistor, but when I connect my PCB, I experience unexpected behavior.
Expected Behavior:
- The 5V source should always have priority.
- If I connect 5V without the battery voltage (6V to 8.4V), I correctly get 5V at the output.
- If I then connect the battery while keeping the 5V source, the output remains at 5V as expected.
- If I connect only the battery without 5V, the output correctly follows the battery voltage.
Issue:
- When the battery is connected first (output = battery voltage) and I then connect 5V, the output switches to 5V for less than 200ms.
- After that, the output voltage drops to ~0.7V, then rises back to 5V in a cycle repeating about 5 times per second.
Additional Details:
- With a resistive load, the behavior is as expected.
- My custom PCB as a load seems to be causing the problem.
- The TPS2121 output is connected to an LDO (TPS7A4533DCQR
Has anyone experienced a similar issue, or does anyone have suggestions on what could be causing this instability? Could it be related to inrush current, startup behavior, or some interaction with the TPS2121's control logic?
Thanks in advance for your help!
