MP2731 - A few beginner general questions

Battery Management
1

Hello!

I’m working on a project to provide power to a device and wanted to use the MP2731 as the battery manager but I have a few questions that are probably pretty basic, but I’m entirely self-taught so I’m sure there’s plenty that is common knowledge that I just don’t know.

Anyways, the questions I have are as follows:

Do I need an external PD Controller like is shown in the reference design if I want to provide power through USB-C to USB-C? I saw that it will handle power negotiation over DP and DM but I know my previous project would only work through a USB-A to USB-C connector.

Can I leave NTC and VNTC disconnected or will I need something connected to them? The batteries I have do not have a thermistor pin, just + & -; it handles thermal management itself.

I apologize if my questions are basic, but I’d rather ask those who know more than I do.

Thank you!

2

Hey @jshive91, Hello!
I am also working on similar kind of project, where need to charge a Li-PO battery. I have used MP2731 and let me assure you it is a good chip to have in your circuit. It is very versatile to use and much configurable, once you have I2C connected.
About your questions, I will answer point wise,

  1. Do I need External PD Controller? Well you can employ one if you want to target the Fast Charging Feature. The PD controller will negotiate the current and voltage with source, and avail you sufficient power for Fast Charge. it basically deals with CC1 and CC2 lines on USB C. If Fast Charging is not what you are looking for then simply ignore the PDC and save much of designing pain. Simply connect CC1 to GND via a 5K1 resistor and you are good to go. In my personal experience connecting both CC1 and CC2 with different 5K1 resistors didn’t worked, so I simply kept CC2 floating.
  2. Its better if you connect the NTC a 10K external and simple one like NXFT15XH103FA1B025 by murata. Just place it close to your battery [pack], so that it will be always touching to the battery.

Good Luck!! And never apologize for asking questions, answering questions works for both, you gain knowledge and the other refreshes. If you need any further help, you can contact me on aaditya[at]denics[dot]in

3

Thank you very much for your answers! I appreciate it.

I do have one additional question though: Do I need to set the configuration every time the device loses power, or can I set it using I2C once and the settings will stay?

4

Hello @jshive91 ,

Like aaditya said, there is no need to apologize for asking questions!
The PD Controller is only needed if you would like to have access to the faster PD charging speeds.
It is not encouraged to leave NTC and VTNC floating, if you are sure the battery will handle thermal management on its own, still add the resistor divider in the DS, size the resistor divider such that the NTC pin believes it is within safe temperatures to charge the battery.
The MP2731 will by default come in its -0001 configuration, you can make changes with i2c but the i2c changes will be non-volatile, meaning the changes will not be permanent. To obtain a costume default config, kindly contact MPS FAEs with the following form:
MPS NOW Technical Support - Contact (monolithicpower.com)

Regards,
Jonathan