I have an Adafruit Feather RP2040 with a li-ion battery charging IC and I was wondering if the charge current is also influenced by the type of USB spec the controller uses. For example, the Adafruit rp2040 is USB 2.0 spec with a connector type C. And IIRC USB 2.0 is max power at 500mA, but is that max power pertaining to the battery charging as well?
I ask because the charging IC has its own current limiter called the programmable resistor. So, I'm confused if the charge current will change if I change the programmable resistor but have the same USB 2.0?
I believe the USB spec has nothing to do with my battery charging IC, but I figured I should ask around incase I am reading this incorrectly.
I think max charge current is only limited by the program resistor on the charging chip.
5k1 sets it to ~200mA, which is a good match for 1Ah (or larger) batteries ( ≤ 20% rule).
The two 5k1 resistors on CC1/2 limit current of the USB-C connector AFAIK to the default 500mA.
Leo..
This circuit requires USB to power both the battery charging and running the circuit concurrently. If you are limited to 500mA on USB, then you have to set the charging current with that in mind. It appears to be set by default to about 200mA charging current, leaving 300mA for the circuit load.
However, it's possible that you could set the charging current to 1A, and the charger would apply as much charge current as it can, if less than that, while powering the circuit as first priority. The datasheet of the charger chip might clarify that. But looking at it simply, this is a linear charger, so it can't supply any charging current at less than the battery voltage - because voltage doesn't flow uphill. So that's going to be a limiting factor for charge current if the input voltage starts to sag. You run the risk that PC USB would shut down if you try to draw too much current, but if you're using a USB power brick with something like 2A capacity, it might work just fine with no sag.
It's not clear why OP is asking this.
The setup is designed to charge a 1Ah (or more) battery with the right (200mA) current.
What needs to be changed...
Yes, you could increase charge current (if you have a larger battery),
But I expect the tiny charging chip getting into thermal trouble quickly, since it's a linear chip.
Leo..
I am thinking about making my own board that has a battery charging chip and I came across Adafruit's feather boards. My battery is 2500mAh and I wanted to charge it at a slightly higher current than 200mAh. The battery is rated at 0.5C so I wanted to understand how power is delivered to it via the USB if the USB is also powering the MCU which uses USB 2.0 spec. I am confused if the MCU USB spec also reflects onto the battery charger IC even though I can change the programmable resistor associated with the battery charger IC.
This limit of 500 mA is only captured on the MCU datasheet about its USB 2.0 protocol. I have this USB micro-B connector that states up to 2100mA charging power.
