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BQ25713EVM-017: Configuration/Charging problem

Part Number: BQ25713EVM-017

Hello. I have been able to communicate with the device over I2C with no problems. I can write and read registers. I am trying to configure the device manually, but so far it does not behave as I expect. 

For the power source I am running into the VIN with a 12V 2A DC power supply. On the VBAT I have connected a 7.4V 5200mAh battery with maxim integrated fuel gauge(has coulomb counter, ammeter, voltmeter) attached. On the VSYS pin I have a load resistor.

By writing registers I have configured the max charge voltage as 8.4V(this is the nominal charge voltage according to the battery spec sheet). I have set VSYS with a min of 7.4V. Both of those values are fine. I can verify them with a multi-meter. When I unplug the power supply, the battery does discharge over the VSYS load providing power. When I plug the power supply back in, the VSYS goes back to the min system voltage that I configured. This behavior appears normal to me.

The problem that I have is with the charge current. I am trying to write the charge current register with 0x0400 to give 1 Amp of charge current. However, no matter what I try, the charge current never changes. It always reads back from the device as either 0x0080(128mA) or 0x0000. 

So it is either trickle charging or not at all. I know there are some operating modes and conditions which cause the device to write 0 or 128mA to the charge current register. I am not sure how to force it into fast charging mode with 1A of charge current. Do I have a configuration problem or some other mis-understanding about how this works? Does the battery have to be dis-charged a lot before quick charge happens??

Here are my configuration registers:

Charge Option 0: 0x020E

Charge Option 1: 0x9210

Charge option 2: 0x0237

Charge option 3: 0x0020

Status register readings:

prochot status: 0xA880

charger status: 0x8000

Although I have a 12V power supply plugged in, the input voltage register only reads 7.7 volts. Is that a problem? What I desire is to power the system with 12V 2A. The internal buck converter should bring that down to 8.4 volts or less at 1A to charge the battery, and 7.4 Volts to the VSYS to power the rest of the system. When the power supply is unplugged, then the VSYS should be provided by the battery.

Do I have some problems in my configuration? Any ideas?

  • Hi There,

    Thanks for asking. 

    I suspect this is related to your input voltage. Could you please check voltage at both 12V power supply output and charger input see if it is really 7.7V. You can also check input impedance as well at charger input side.From the status bit REG 22H[7]=1 can verify that converter is under VINDPM. And charging is giving its priority to system when VINDPM is triggered. 

    How many system load is added during this test. Does it overload the power supply and drag down power supply output voltage?

    Regards

  • Hello. Thank you for this response. 

    I have changed the power supply to a more robust model suitable for test benching. I can measure the input voltage at 12V across the VIN test points. I have also measured 12V at the VBUS capacitor.

    However, I still cannot write anything into the charge current register although I am not in VDPM status. Charge current reading is 0x0000.

    Reading the input voltage register gives 0x1E00, or 7.680V. I cannot overwrite into this register with the proper voltage(12V). I suppose the host updates this register with a value based on what it sees at the input.

    I also removed the battery and the load from the system and measured again. Same results. VIN and VBUS at 12V. Then I read the input voltage register(0B0A) and I get this reading of 7.680V. 

    Current status register readings:

    Charge Status: 0x8000

    prochot status: 0xA800

    I am not sure what else to try here.

    ..

  • Thanks again. Everything is now working as it should. The problem was not the input power supply, but I got it all resolved by resetting all registers and starting over from 0. 

    Shishuo Zhao said:

    Hi There,

    Thanks for asking. 

    I suspect this is related to your input voltage. Could you please check voltage at both 12V power supply output and charger input see if it is really 7.7V. You can also check input impedance as well at charger input side.From the status bit REG 22H[7]=1 can verify that converter is under VINDPM. And charging is giving its priority to system when VINDPM is triggered. 

    How many system load is added during this test. Does it overload the power supply and drag down power supply output voltage?

    Regards