BQ25303J: Diode necessary?

Maria Senyer

Prodigy 70 points

Part Number: BQ25303J

Tool/software:

Dear Technical Service,

I followed the recommnedations from one of your colleagues about the BQ25303 and I designed this circuit:

Now what I got is that if I have D1 placed I see a significant voltage drop between VBAT and VBUS.

For example, for a battery of 3.7V I see a drop of about ~0.7V.

Is this diode strictly necessary?

Thanks,

7 months ago

0 Maria Senyer 7 months ago

Prodigy 70 points

In an attempt to reduce the drop voltage in the diode I wanted to use a Schottky.
What should be the If (forward current) specification of this diode?

Thanks

0 Ning T 7 months ago in reply to Maria Senyer

TI__Guru 57821 points

Hi,

Please refer to https://e2e.ti.com/support/power-management-group/1447949/bq25306-schematic-review

Thanks,

Ning.

0 Maria Senyer 7 months ago in reply to Ning T

Prodigy 70 points

Hello, the link is broken. It says "Page Not Found".

0 Ning T 7 months ago in reply to Maria Senyer

TI__Guru 57821 points

Hi,

You may try something similar to 1N4148.

Thanks,

Ning

0 Maria Senyer 7 months ago in reply to Ning T

Prodigy 70 points

Hi.

I already tried 1N4148, it is written in the schematic, I used this specific part and this is where I got the problem.

Do you have any other suggestions?

0 Ning T 7 months ago in reply to Maria Senyer

TI__Guru 57821 points

Hi,

We are checking and will get back to you.

Thanks,

Ning

0 Maria Senyer 7 months ago in reply to Ning T

Prodigy 70 points

Hi, okay. Looking forward to your answer.

0 Ning T 7 months ago in reply to Maria Senyer

TI__Guru 57821 points

Hi,

Please try to add another diode to block the TP1 voltage from going back to VBUS.

Thanks,

Ning.

0 Maria Senyer 7 months ago in reply to Ning T

Prodigy 70 points

What is your suggestion here? I find it quite unspecific

0 Ning T 7 months ago in reply to Maria Senyer

TI__Guru 57821 points

Hi,

We are working on it and will get back to you.

Thanks,

Ning.

0 Ning T 7 months ago in reply to Ning T

TI__Guru 57821 points

Hi,

Referring to Figure 10-7. Typical Application Diagram with Power Path on the d/s, Q1 body diode blocks the VSYS voltage from going back to VBUS. When using VBUS instead of PMID as VSYS, there's no isolation between VSYS and VBUS any more. Please try to add a diode to separate VSYS and VBUS.

Thanks,

Ning,

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BQ25303J: Diode necessary?