Other Parts Discussed in Thread: PMP7355, , , TPS23753
I have implemented a PMP7355 design on a custom board, which connects to a TPS65217C PMIC chip, and the LED connected to the SYS output pin flashes for about 50ms once.
Scoping the output of the 5V PoE shows a saw tooth of 4.7V to 7.5V at 20Hz. This is preventing the PMIC from starting up.
Our custom PMP7355 design has the following parts substituted:
1. R18 is 0.22 ohms, so that extra current allowed for 12V AUX input operation, delivering 10W output.
2. T2 is a POE13F-50L, which is different in inductance and turns (still 5V output) from the original POE13P-50L flyback used in PMP7355
3. A current sense resistor (10 mOhms at 1W) inserted between VDD and VDD1 pins for current measurements.
Does anyone have any ideas on how to fix this?
In parallel to this I will obtain a TPS23753AEVM-004 board and swap out the components for 5V operation, and test with a TPS65217C evaluation board.
The requirement of our design is 5V at 10W output, and the PoE transformer needs to be lower than 10mm height to fit in the enclosure, hence the use of POE13F-50L or HA3802-BL from Coilcraft.
Thanks in advance,
SAGE Automation - Australia