BQ25751: Do you have any parts calculation tool for peripheral parts of BQ25751?

Kazuya Nakai59

Guru 21845 points

Part Number: BQ25751

Tool/software:

Hello guys,

One of my customers is considering using BQ25751 for their new products.

At this moment, they have the following question.
Could you please give me your reply?

Q.
If TI have any parts calculation tool for peripheral parts of BQ25751, they want to use it.
Do you have it?
If not, is the way to calculate the peripheral parts the calculation method written in the device datasheet only?

Your reply would be much appreciated.

Best regards,
Kazuya.

4 months ago

0 Christian Moyer 4 months ago

TI__Mastermind 36076 points

Hello Kazuya,

I recommend refering to our BQ2575X calaculation tool:https://www.ti.com/tool/download/BQ25756-DESIGN-CALC/

Best Regards,

Christian.

0 Kazuya Nakai59 4 months ago in reply to Christian Moyer

Guru 21845 points

Hello Christian,

Thank you very much for your reply.

Is there any document explains how to select external switching MOSFET for BQ25751?

Thank you again and best regards,
Kazuya.

0 Christian Moyer 4 months ago in reply to Kazuya Nakai59

TI__Mastermind 36076 points

Hello Kazuya,

Yes, I recommend refering to our appnote regarding MOSFET selection:sluaax9.pdf

Best Regards,

Christian

0 Kazuya Nakai59 4 months ago in reply to Christian Moyer

Guru 21845 points

Hello Christian,

Thank you very much for your supports.

Could I ask you about the calculation tool?

The tool says that Input/Output minimum capacitor is 160uF.
But BQ25751 EVM has about 100uF as Input/Output capacitor each. It is smaller than calculation tool.

Is this no problem? Is the minimum capacitor value the tool says not needed to follow?

Your reply would be much appreciated.

Thank you again and best regards,
Kazuya.

0 Christian Moyer 4 months ago in reply to Kazuya Nakai59

TI__Mastermind 36076 points

Hello Kazuya,

I'm not sure why the calculation tool says the minimum value is 160uF. The Correct minimum value is 80uF after derating, the recommend is 160uF.

Best regards,

Christiam

0 Kazuya Nakai59 4 months ago in reply to Christian Moyer

Guru 21845 points

Hello Christiam,

Thank you very much for your supports.

I tell them that the minimum INPUT/OUTPUT value are 80uF and they understood it.

They have an additional question as the follow.
Could you please give me your reply?

Q.
The calculation tool doesn't show the recommended NMOS FET VDS and IDS.
Could you please tell me how to determine the VDS and IDS?

Thank you again and best regards,
Kazuya.

0 Christian Moyer 4 months ago in reply to Kazuya Nakai59

TI__Mastermind 36076 points

Hello Kazuya,

I recommend choosing a VDS rating at least 20–30% higher than the maximum input voltage to provide adequate margin.

For example, if your input voltage goes up to 24 V, a FET rated for ≥30 V is recommended

I recomend choosing the IDS rating based on the maximum input/charge current.

Include a safety margin (typically 1.5× to 2× the maximum expected current).
For instance, if the peak input current is 5 A, select a FET rated for ≥7.5–10 A.

Best regards,

Christian

0 Kazuya Nakai59 3 months ago in reply to Christian Moyer

Guru 21845 points

Hello Christian,

Thank you very much for your strong supports.

Your reply was very helpful for the customer and me.
I will close this thread.

But the customer has an other question about BQ25751.
So I will ask it on other thread.

Thank you again and best regards,
Kazuya.

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BQ25751: Do you have any parts calculation tool for peripheral parts of BQ25751?