About current monitor of Iset pin at bq25100

Satoshi

Guru 19645 points

Other Parts Discussed in Thread: BQ24045, BQ25100

I want to monitor charge current from ISET-pin ( R_ISET).

I think that charge current and ISET current are proportional relation.

Please let me know about the proportional ratio of Charge current and ISET current.

※For example, bq2407x's ISET is 1/400 (±10%) of the charge current.

Best regards,

Satoshi

over 10 years ago

0 Wenjia Liu over 10 years ago

TI__Expert 7730 points

VISET is regulated to 1.5V during fast charging. In constant voltage stage, the VISET will start dropping as the charging current is tapering down. The ratio is about 90.

Thanks,

Wenjia

0 Satoshi over 10 years ago in reply to Wenjia Liu

Guru 19645 points

Dear Wenjia Liu-san

Thank you for reply.
Is it right by the following calculation?

・Iout：200mA
⇒R_ISET=K_ISET/Iout
=135/0.2
=675Ω

・If Icharge：100mA
V_ISET=Icharge/(R_ISET*90)
=0.1/(675*90)
=1.6μV

※I think that V_ISET is too small.

Best regards,
Satoshi

0 Wenjia Liu over 10 years ago in reply to Satoshi

TI__Expert 7730 points

Hello Satoshi-san,

Your first part of calculation is correct. In the second part:

V_ISET = RISET * I_ISET = 675 * (ICHG/90) = 675 * (0.1/90) = 0.75V.

I hope this makes sense to you.

Thanks,

Wenjia

0 Satoshi over 10 years ago in reply to Wenjia Liu

Guru 19645 points

Dear Liu-san

Thank you for many reply.
Sorry for additional question.
Customer begin to checking bq24045.

Please let me know about ratio of bq24045, too.
(ex, bq25100 is "90")

Best regards,
Satoshi

0 Wenjia Liu over 10 years ago in reply to Satoshi

TI__Expert 7730 points

Satoshi-san, For bq24045, the ratio is about 360. Thanks, Wenjia

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About current monitor of Iset pin at bq25100