MP2722 and USB PD adapters

Battery Management
1

Hello, I am thinking about using MP2722 for battery management. I assumed, that it could do USB PD negotiation, since datasheet mentioned <26V Vin, but this does not seem to be the case. The biggest problem is, that some of these adapters do not output 5V by default and when I connect it to my device, it does not charge at all. All registers read as if nothing was plugged to USB C port at all.

So I have 2 questions:

  • Is there a way to make the PD adapter output 5V, while preserving charger detection and sourcing current to Vin? I can poll registers and set max current to safe-ish value if this was possible. Actually, no, I will assume PD adapter and crank current up to 11 lol.
  • Is there chip, that does PD negotiation and can do at least 5A charge current? I saw MP2731 mentioned in some blogpost, that it can do PD, but looking at datasheet, it does not mention this feature directly.
2

The MP2722 is not a USB PD controller. It just can handshake via CC lines (or D+/D- in case of USB BC1.2). This means it detects the CC line resitors, which signal the capabilities of the USB source.

USB PD on the other hand is based on a data protocol where the USB source and the sink exchange data packages via the CC lines.
These packages include the advertised capabilities of the USB source (a set of fixed profiles in context of PDO) and in return the sink sends the selelected profile.

If the adapter is non standard and not based on USB specs (e.g. the pull-up are not valid), chances are that the MP2722 won’t even fallback to legacy USB A (5 V/0.5 A).
You can check the status and fault registers to see if they hold any information.

Additionally, the 26 V you are referring to are absolute max ratings. The opoeration voltage range is 3.9 V - 16 V.

Hence, an adapter that provides >16 V may trigger the over voltage protection.
The failure registers will tell you about such an event.ected profile. That’s a brief “summary”.

So the MP2722 only supports dumb chargers.

Now, if your adapter is a USB PD adapter (smart charger) then it expects a USB PD sink on the other end. Your MP2722 does not speak USB PD so it sees nothing. It only checks for CC line resitors which are not complaint with any charging source.

If you want to support USB PD you have two options:

  1. Use an external USB PDC controller that performs all the negotiation. It then writes the result (the selected contract) to a register which your MCU then reads via I²C. Then configure the MP2722 via I²C based on this negotiated contract and allow MP2722 to start charging.
  2. Find another device that integrates a charger and a fully compliant USB PD controller.

I would recommend 1) as it also allows for better power management (which could be crucial in your battery powered application). For example, you can only power the USB PD controller when you have detected a USB reconnect event (by sensing VBUS) and leave it fully unpoowered for the majority of the time.
You also don’t rely on an integrated solution that does it all. For example, by adding a front-end USB PD controller you can simply add USB PD 3.1 PPS support to your system. I guess you had a hard time looking for an integrated solution that supports this.

Of course, third option is to accept the limitations and that your device won’t be able to support USB PD. USB 3.1 or USB 3.2 still enables fast charging at 15 W (5 V/3 A) via simple CC line resistor detection.

The MP2770 can charge up to 6 A. Same applies to the MP2760 (which also allows to feed you SYS with 6 A opposed to the 3.65 A of the MP2770 and supports input voltages up to 20 V). MP2770 is also pure single cell.