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Need a USB charging port part suggestion

Soumitra Bhattacharjee
Intellectual 820 points
Other Parts Discussed in Thread: BQ24232H

Hi

I have a portable device with a Li-on battery that gets charged via a constant current of 100mA from the USB port and an inbuilt charging IC.

However i have a concern regarding the kind of power source/USB port it could possibly be connected to. A USB 2/3 without enumeration or high power charger could kill the device. 

What i am looking for is a part that can help identify if i'm connected to a 100mA source (USB 2 for ex.) so i can directly use this to charge OR if the device is connected to a high power source (USB 3/wall /fast charger) then to switch it through a current limiting circuit.

Any help is appreciated.

Thanks and regards

  • 0
    TI__Mastermind 33091 points
    I suggest you look at this part www.ti.com/.../tps2552-1

    It will allow you to set your current limit accurately down to 75mA. This device will prevent you from drawing more than your target current from the source.

    I don't typically support this device, but I am happy to help or you can submit any questions to the E2E forum and you will get someone with more direct knowledge than me.
  • 0 in reply to Chuck Branch
    Intellectual 820 points
    Hi Chuck
    Thanks for your reply. I did go through it and a few more power/load switches but you see, in my case my actual power requirement is 0.5W to 1W (keeping a little headroom) and a typical fast charger could output approx 10w-15w. This is a lot of power dissipation for a linear device.

    To approach the issue from another direction, is there any device which, after USB enumeration, can either flag the source as low power (5v, 100-500mA) or high power (5v, >500mA) ?
  • 0 in reply to Soumitra Bhattacharjee
    TI__Mastermind 33091 points
    The host/UFP port provides up to 500mA/900mA depending on USB 2.0 vs 3.0 requirements and your device is required to be at or below this level of current. If you only draw 100mA, you will be within the UFP limits.

    If you are a device, then there is no need for the power source port to be limited in the amount of power to be delivered to you, your battery charging device should provide current control into your battery.

    I am not an expert in TI's lithium Ion battery charging portfolio, but my best guess is you should look into a part similar to the BQ24232H.
  • 0 in reply to Chuck Branch
    Intellectual 820 points
    Thank you Chuck. I guess i'll have to redesign the charging section a bit to take this issue into account.