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LiPo battery charger design

Tony Jose1
Prodigy 30 points
Other Parts Discussed in Thread: BQ25155, BQ25100, TPS61099, BQ25120

Hi,

I was directed here from your support case CS0183696.

We are designing a charging circuitry for recharging our device which consists of a 65mah 4.2V LiPo battery. This charging dock(pic below) consists of a 750mAh(or 500mAh) 4.2V LiPo battery, a Usb-C connector and Led circuitry to show battery percentage of 750mAh battery.
The following are the charging scenarios.
1. Whenever the device is connected to the charging dock via its magnetic connector, the 65mAh battery inside the device gets charged using the 750mAh battery inside the dock.
2. If you connect the usb-c connector inside the dock to a laptop/power_outlet, this charges the 750mAh battery inside the dock. If the finger unit is connected to the dock at this time, the 65mAh battery gets charged simultaneously by the Usb power.
3. Whenever a Usb connector is connected, the battery level of 750mAh battery is displayed using 4 leds inside the dock. In other times, this battery level can be seen if user pushes a button on the led indicator pcb board, in the dock.
Please see our initial block diagram design of the charging circuitry inside the dock. USB input to STEP UP is for cutting down the BATTERY-1 (750mAh) output when USB voltage output is present.
The datasheets of the battery are attached here.
Please let us know your comments/review on this design w.r.t our charging needs/scenarios. Please let us know, which battery charger or PMICs and Stepup do you reccommend for our new design?
  • 0
    TI__Mastermind 21590 points

    Hello,

    For the first PMIC, take a looks at the BQ25155. This device is a 500mA charger with an integrated ADC which can be used to determine LED level after measuring battery voltage. The TPS61099 is a low Iq boost converter. The second PMIC can also be the BQ25155 or the BQ25100 which is a small 250mA charge with low Iq and low termination. 

  • 0 in reply to Raheem
    Prodigy 30 points

    Hi Raheem,

    I notice that many such parts are I2C controlled. Our deice doesnt have a host IC in the charging dock and we dont want to add more components. Dooes these i2c controlled parts need a host IC coonnected to it all the time and communication to be maintained? Or can we setup these parts programmed to desired settings just first time and it will work on its own w/o the need of additional host? Please explain tthe differences, so that we can chose the right part asap.

  • 0 in reply to Tony Jose1
    TI__Mastermind 21590 points

    Hello Tony,

    Yes the BQ25155 needs host control but the BQ25100 is standalone. The BQ25120 can be used without host control.

  • 0 in reply to Raheem
    Prodigy 30 points

    Hi Raheem,

    We plan to use standalone charging ICs. Then we need to show battery charge level of the 750mAh Lipo battery.using 4 LEDs. Do you have any part suggestions for this fuel guage circuitry. We want standalone partss as our design doesn't have a host MCU in the charging dock for I2C interface. Our main design need includes:

    1. Show charge level continuously if USB(Vin) is connected.

    2. All other times, whenever you press a button, LEDs lightup for 5 sec to show charge level.

    If your options are I2C based, is there anyway to use it without adding a host MCU to the circuitry? Will you provide them pre-programmed so that we dont need a host.

  • 0 in reply to Tony Jose1
    TI__Mastermind 21590 points

    Hello,

    We have fuel gauges. However, they're all connected and need a MCU for operation. Most battery monitoring to show the battery level will require some form of communication.