I'm working on a project to update a device to use a Li-Ion battery rather than non-rechargables. I would like it to be charged via USB-C.
I have previously used IP2721 to handle the power delivery negotiation but have recently found this chip (MAX77751) which looks like it can handle the PD negotiation and the battery charging in a single IC. It also doesn't need to be configured by a microprocessor which is very useful for my project.
My issue is with the USB-C connector. The IC requires CC1, CC2, D+ and D- in order to negotiate the current draw. I am struggling to find a USB-C connector with these signals available. The PCBs will be soldered by hand so the fewer pins on the connector the better (Not sure I have a steady enough hand to solder a 24-pin connector).
I have found a connector which fits my requirement (Datasheet) but it only has CC1 and SBU1. Would this be able to correctly negotiate PD with only one CC signal?
Alternatively, I found another connector (Datasheet) which has both CC1/CC2 signals but no D+/D-. What would the limitations be if I used this connector? I assume I would lose BC1.2 detection. With a Type C power brick I'm guessing this would be fine but if I used a legacy USB-A power brick with a "Type A-Type C" cable would it work at all?
It's quite a large battery (10000 mAh) so I'd rather not be limited to 500 mA charging if the negotiation fails.
Best Answer
USB PD on Type-C does not use the DP/DN pins, only the CC pins. Or rather, only one pin at a time, and the pin depends on which orientation you plug in the cable to connector.
The first connector with only one CC pin will only work in one orientation, as there is only one CC wire in a cable.
The second connector with no DP/DN pins cannot negotiate BC and won't work with BC supplies with Type-A supplies. As it cannot enumerate with a host, it cannot draw even 500mA, because to draw more than 100mA, it must be requested from host if it is OK to draw more than 100mA.