BQ24171: The charging current is different between the actual value and the set value

Conor

Guru 10605 points

Part Number: BQ24171

Tool/software:

Hi,

The BQ24171 is mounted on a custom board and evaluated.

The charging current is set to 884mA, but the actual value is about 1A, which is quite large.

Even if it take into account the tolerance of VREF and resistors, it is about ±1% of the set value, so I don't think the actual value should be so high.

Do you have any ideas why this might be? If you need a circuit diagram, I can share it with you in a private message.

Thanks,

Conor

6 months ago

0 Jing Zou 6 months ago

TI__Mastermind 20280 points

Hi Conor,

Can you please share the schematic on the charging circuit so we can further look into the issue? Thanks.

0 Conor 6 months ago in reply to Jing Zou

Guru 10605 points

Hi Jing,

I would like to send you the schematics for the custom board via private message, so could you please give me permission to private message you?

Thanks,

Conor

0 Conor 6 months ago in reply to Jing Zou

Guru 10605 points

Hi Jing,

Just a reminder.
Please accept the private message. Or share your email address?

Thanks,

Conor

0 Jing Zou 6 months ago in reply to Conor

TI__Mastermind 20280 points

Hi Conor,

We just get back from US holiday. Our apps support for this device will reach out to you later this week for the schematic file. Thanks for your understanding.

0 Conor 6 months ago in reply to Jing Zou

Guru 10605 points

Hi Jing,

I haven't sent you the schematics yet, but would it be possible to share them via private message or email?

Thanks,

Conor

0 Conor 6 months ago in reply to Conor

Guru 10605 points

Or, if it takes time to check the circuit diagram, please comment first with possible reasons why the actual charging current is different from the set value.

0 Christian Moyer 6 months ago in reply to Conor

TI__Mastermind 22040 points

Hello Conor,

I'm sorry for the delay TI was on Holiday this last weekend. I am the Apps support for this product. Can you send me the schematic via private message?

Thank You.

Christian.

0 Conor 6 months ago in reply to Christian Moyer

Guru 10605 points

Hi Christian,

There may be no need to share the circuit diagram. The RSR between SRP and SRN is 20mΩ, and the resistors connected to the ISET terminal are 100kΩ on the Vref side and 12kΩ on the GND side. With these resistance values, the charging current setting is 884mA.

However, if 20mΩ is used for RSR and the charging current setting (884mA) flows, V(SRP-SRN) is about 17.7mV and the charging current accuracy is about ±7%. This may result in an error of nearly 1A in some cases. Is my understanding correct?

For details, please refer to the following thread.
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/889235/bq24171-charge-current?tisearch=e2e-sitesearch&keymatch=BQ24171%20current

Thanks,

Conor

+1 Christian Moyer 6 months ago in reply to Conor

TI__Mastermind 22040 points

Hello Conor,

Conor said:
However, if 20mΩ is used for RSR and the charging current setting (884mA) flows, V(SRP-SRN) is about 17.7mV and the charging current accuracy is about ±7%. This may result in an error of nearly 1A in some cases. Is my understanding correct?

Yes, your understanding is correct, this is most likely the cause of the variance between the set charge current and the actual charge current

Best Regards,

Christian.

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BQ24171: The charging current is different between the actual value and the set value