Tool/software:
Hi TI support,
I have a question regarding output rectification. I can provide the schematic offline if needed.
Background:
Designed the TPS23758 into a client product that requires a 4W supply with diode-OR power sources:
- Isolated PoE with 24VDC auxiliary input, 5VDC output
- USB 3.0 power input, 4.6VDC output
- Backup battery, 4.2VDC output
Prototype testing revealed that the PoE secondary side synchronous FET cannot double as a diode-OR without complications. For example, repowering PoE to take over from USB caused a current surge and the PoE DC/DC would not consistently restart.
Thus, an additional Schottky was added immediately after the PoE synchronous FET, which had little impact on the TPS23758 output regulation.
Question:
In previous posts on this forum, TI engineers discouraged using a diode rectifier output for TPS23758. Are there any reasons for that other than efficiency? Currently both the FET and separate Schottky are on board, and the FET is now of course redundant. Other larger TI solutions are not desirable because the PCA is space constrained.
Thank you,
Mark
