I am encountering a problem using the TPS23861 in semi-auto mode.
In auto mode everything works fine. When I plug a PD into a port, I see detection, classification, and power up fine for class (0-4). Two event classification is also working.
In semi-auto mode, I have detect and classification enabled (register 0x14 set to 0xFF, DETE and CLE bits set for all ports)
When a PD is connected, I can see detection and classification occurring properly.
When I set the power enable push button register PWONx bit to 1, power to the port is enabled,.
The problem is that there is approximately a 1ms period after the classification and before power is enabled where the voltage drops below the MARK level. This is causing a problem for some PD especially class 4. Class 4 devices are not seeing our device as a class 2 PSE probably because the drop below mark level is causing the PD to reset and so it will not see the second classification event.
I do not have an oscilloscope screen shot right now, but below shows what I am seeing. The trace marked in red is what I see in semi-auto mode. In auto mode, I do not see this drop out.
The data sheet section 7.4.3 explains that in semi auto mode, a new detection/classification will occur after the PWON bit is set if needed to meet the 400ms detection to power on time limit, but it looks like there is some period after classification and before power on where the output is not being driven.
Any help is appreciated.