BQ25730: 400k loop compensation for 800k application

Kailun Liu

Part Number: BQ25730

Dear expert,

Our charging input voltage is 24V, battery voltage is 21V, and charging current is 2A.

Currently, we have chosen a 4.7uH inductor. According to Table 8-5 in the datasheet, the 4.7uH inductor only corresponds to a 400KHz switching frequency setting.

However, we want to use an 800KHz switching frequency to reduce ripple current.

Is this reasonable, and what are the potential impacts? If using 800KHz, how should the loop compensation be adjusted?

5 months ago

0 Christian Moyer 5 months ago

TI__Mastermind 48478 points

Hello Kailun,

I recommend switching to a 3.3uH or a 2.2uH inductor, since 4.7uH is not recommended for 400kHz switching frequency.

Best Regards,

Christian.

0 Kailun Liu 5 months ago in reply to Christian Moyer

TI__Expert 4123 points

Thank you Christian.

Does customer need to adjust comp R and comp C as well? Is there any side effect if they kept using 4.7uH? Less stable bandwith?

0 Christian Moyer 5 months ago in reply to Kailun Liu

TI__Mastermind 48478 points

Hello Kailun,

Yes, They will need to adjust their comp R and comp C as well

Kailun Liu said:
Is there any side effect if they kept using 4.7uH? Less stable bandwith?

It's not recommended using 4.7uH with the 400khz, yes it can lead to stability issues.

Best Regards,

Christian.

0 Kailun Liu 5 months ago in reply to Christian Moyer

TI__Expert 4123 points

Thanks Christian.

May I know what is the difference of two 800kHz configuration? There are two setting of 800kHz.

0 Christian Moyer 5 months ago in reply to Kailun Liu

TI__Mastermind 48478 points

Hello Kailun,

Yes, it is dependent on the inductor selection.

If you want to use the 3.3uH, you have to set up the compensation as shown in the table

Same for the 2.2uH inductor:

Best Regards,

Christian.

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BQ25730: 400k loop compensation for 800k application