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BQ25895: BQ25895 with No battery operation

SUMIT RANJAN
Expert 2005 points
Part Number: BQ25895

Tool/software:

Dear texas Team,

On quick note, can you please check this attached schematic and confirm if all good.

Below is the use case:

1. We will be running on the 5V power adapter.

2. No USB signal will be connected with battery charger.

3. no OTG operation is required. 

4. System load current won't be more than 3A current.

5. Input current setting will be done by using the register configuration.

Another query: we will be using in some cases with no battery operation as well means battery won't be connected so output will be in PWM form? 

In case of yes then what will be the average voltage which we will be having on the VCC_SYS rail? 

Minimum and maximum voltage value required in case of no battery mode operation?

Is there any way to regulate the output voltage (VCC_SYS) in case of no battery operation?

SCHEMATIC1 P12_BATTERY_CHARGE.pdf

  • +1
    TI__Mastermind 25805 points

    Hello, 

    Please see my comments below. 

    I have reviewed the schematic and have the following comment. 

    -Since you mention no OTG operation is required please short OTG pin to ground. OTG pin should not be left floating. 

    Beyond the OTG pin the rest of the schematic looks good to me. 

    SUMIT RANJAN said:
    we will be using in some cases with no battery operation as well means battery won't be connected so output will be in PWM form? 

    For operation without a battery it is recommended to disable charge via either CHG_CONFIG bit in REG03 or pull /CE high. The SYS pin output will be a DC voltage as shown in application curves waveforms on datasheet page 51. With no battery connected and charge disabled SYS will be regulated above SYS_MIN setting (default 3.5V). 

    When a battery is connected the minimum SYS voltage with 5V input will still be SYS_MIN threshold. Then maximum voltage SYS will be regulated at is equal to 4.2V plus the voltage drop across Q4 BATFET from SYS to BAT. The voltage drop across BATFET will vary depending on charge current at that time. 

    Best Regards,

    Garrett