BQ25713B: BQ25713 ADC Input current reading problem during CC charging

Di Ma

Intellectual 420 points

Part Number: BQ25713B
Other Parts Discussed in Thread: BQ25713, BQSTUDIO, EV2400

Hello team,

I'm working on MPPT project with 2S2P Li-Ion battery pack.

I'm facing a problem while reading the input current from 0x2A register.

Below you can find my schematics:

Below you can find all registers readings:

I have also made a table with both CC and CV charging:

As you can see from the table, once the charger passes to CV phase of charging (battery voltage = 8384) I start reading the actual input current, until that point I mostly read 200 mA and then the reading starts increasing till the right value.

I have tried soldering a new BQ25713 to the board thinking that I may have damaged some internal electronics while reading the voltage of the resistors.

I can also read the correct input current by reading the voltage on the sense resistor R10 (Rac).

Also one thing I have discovered is if i connect a load (4.7 ohm 25 W ceramic resistor) to the VOUT terminal while disconnecting the battery, I get the right reading from 0x2A register. If I connect the battery back and disconnect the load again I read the wrong input current value.

Could you help me with this problem since I'm out of ideas what can I be possibly doing wrong here.

Thanks in advance,

Dmitriy

over 4 years ago

0 Di Ma over 4 years ago

Intellectual 420 points

Here is the registers values for CV charging:

As you can see now I'm reading a value of 20 (20*50mA=1000 mA)

0 Di Ma over 4 years ago

Intellectual 420 points

Here is the registers values for CV charging:

As you can see now I'm reading a value of 20 (20*50mA=1000 mA)

0 Kedar Manishankar over 4 years ago in reply to Di Ma

TI__Mastermind 24075 points

Hi Dimitriy,

Let me test based off of your configuration to verify I_IN ADC behavior. I will get back to you by 10/19.

0 Tiger Zhou over 4 years ago in reply to Kedar Manishankar

TI__Mastermind 33385 points

Hi, Dmitriy,

Our EVM data shows IIN ADC readout matches the power supply readout.

20V ADAPTER, 7VBATTERY, 2S
ICHG(A)	IBUS(SUPPLY) (A)	IBUS(0X2A) (mA)
3	1.37	1300
2.5	1	950
2	0.82	750
1.5	0.59	550
1	0.41	400
0.5	0.22	150
0	0.01	0

0 Di Ma over 4 years ago in reply to Tiger Zhou

Intellectual 420 points

Thank you for your response,

As I can see from the decreasing charging current, you are in the CV charging phase. I am also reading the right value of the input current during CV charging phase.

I'm having problem reading the input current during CC charging phase.

There is something that changes the behaviour of the charger during CC phase. Even though I set different maximum charging values again I am reading the wrong input current.

I'm trying with connecting the load to VOUT terminal, by changing the Min_Sys_Voltage, I get different voltages on the output -> consequently different current though the load. I read the input current correctly with load. Once I connect the battery and start charging the battery in CC mode I start reading wrong values.

What changes in the charger when I start charging the battery?

0 Tiger Zhou over 4 years ago in reply to Di Ma

TI__Mastermind 33385 points

My test data have no particular sequence order. They are in CC mode.

0 Di Ma over 4 years ago in reply to Tiger Zhou

Intellectual 420 points

OK, so as I understood from your answers, you have proved that the EVM of BQ25713 is working fine, great!

What about my problem? Do you have any idea why I'm facing it?

0 Tiger Zhou over 4 years ago in reply to Di Ma

TI__Mastermind 33385 points

Suggest polling the registers using an alternative way, such as EV2400 and BQStudio.

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BQ25713B: BQ25713 ADC Input current reading problem during CC charging