D-/D+ lines in USB2 BC on MP2722/4

Battery Management
1

Hello!

In this ticket I saw an answer regarding the use of MP2724 for USB2 power alongside the USB2 data lines.
This section

A simpler solution overall would be to keep the data lines routed directly to your MCU and to connect the USB VBUS to the MP2724 to enable charging. This would keep your design simple and straightforward.

Seems to indicate that simply connecting the data lines to the MCU, and the 5V and GND to the MP2724 will allow me to both communicate with my MCU and charge via the USB connection and the MP2724. My question is what charging current can I expect with this setup, as I think USB2 BC requires the data lines to coordinate higher than 500mA on a USB2 connection.
In the solution described, unless I’m mistaken, the data lines are not routed to the MP2724 at all, and so the higher USB BC1.2 currents will not be achieved.

Am I correct?
Thanks!

2

Good question, I remember addressing this previous ticket.

If you want to support higher currents (like 1.5A for example) through USB2 using the MP2722 and the MP2724, the data lines would need to be handled properly for BC1.2 meaning:

  • Connecting D+/D- to the MP2722/4 directly as mentioned
  • Or have the MCU handle BC1.2 negotiation and tell the MP2722/4 via control pins or I2C. Of course this would depend on your setup.

It is right to be cautious, and you are correct in your thinking. Unless the MCU somehow performs the detection AND tells the MP2722/4 “hey, this is a charging port, allow more than 500mA,” you won’t get the full charging current.

Hope that provides some insight. Let me know if there are additional questions on this subject.

Best,
Krishan