Back powered through resistors, can't detect source attach until full reset #1
Description
Hello,
I'm using this board and have an issue with detecting successive source attachments.
Procedure:
- Board is connected to an RP2040 by four pins: SDA, SCL, GND, and 3.3V in
- Plug in USB C source
- Source is detected, chip registers have the PDO profiles, etc
- Remove USB C source
- Plug in USB C source
- Chip does not detect USB C, LEDs do not light, I2C interface is not available
- Power cycle 3.3V in: the chip resets and detects USB C source
I am guess that this is caused by back powering through the level shifting FETs from the 3.3V pullup resistors.
One work around is to power 3.3V in from the 5V output from the step down regulator. Then when USB is disconnected 3.3v is also disabled.
A design work around would be to power the pull-ups from the V5V pin of the chip, which can source 30mA and will also power cycle with VUSB.
Has anyone experienced this or have a work around?