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BQ25606: Charging Circut with BQ27220 gauge and BQ279XX protection

Timo Klaas
Prodigy 20 points
Part Number: BQ25606
Other Parts Discussed in Thread: BQ27220

I try to develop a charging circut based on the charging-IC BQ25606, the gauge-IC BQ27220 gauge and BQ279XX for cell protection purpose based on the EVM kits. 

You can see what I came up with down below. 

The battery will be an 18650. I would like to charge it with around 1A charging current. The load will be around 50mA.

Before producing the first prototype layout for further testing, I would like someone to check my powerpath design.

Thank you very much!

kind regards

T. Klaas

  • 0
    TI__Mastermind 25800 points
    Hey T. Klaas,

    I could not find the Protection circuit you listed in our database, the bq27xx1. Could you link the exact part number you would use? Its like the bq297xx Protection family, but please confirm.

    In regards to the bq25606, there are a few things to consider:
    The BAT pin, listed here is V+ requires a 10uF capacitor very close to the IC for stability and filtering.
    Both the /PG and STAT pins do not have any pull-up to any rail. Is this off-site or will these pins not be utilized?

    The Protection circuit (if you are using the bq297xx family):
    Please follow the design procedure of the datasheet of the this part in section 10.2.2 - Detailed Design Procedure for the FET selection. It is also recommended to place a 5Mohm resistance across the Gate-Source of each FET (COUT to GND and DOUT to BAT-).

    Everything else looks fine from the start. There are some nets that do not seem accounted for like the +3V3 net, which I guess is off-site somewhere. Also, please note that both thermistors R3 and R13 should be R(25C) of 10k, with B25/85 = 3435 for proper function based on the resistor divider and parts you selected.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 20 points
    Hey Joel,

    Thanks for your reply.
    I added the missing capacitor. I do not plan to use the STAT and the !PG pin because I do not need an optical charge indication and the host mcu can use the information provided by the BQ27220 to show the charging process instead. Or are there any reasons to do it different? How should I connect the pins if not in use?

    I want to use an IC from the bq297xx family, the part was named wrong in my schematic. I will add the 5Mohm resistors.

    Regards,
    Timo
  • 0 in reply to Timo Klaas
    TI__Mastermind 25800 points
    Hey Timo,

    You may leave the STAT and /PG pins floating.


    Regards,
    Joel H