BQ25302: Why is a fault happened when 1ohm register is connected to the capacitor between BTST and SW terminal in series?

Kazuya Nakai59

Part Number: BQ25302

Hello guys,

One of my customers is evaluating BQ25302 on their own board for new products.
They measured EMI level of the board. As the result, the EMI level was exceeded EMI level limit around 40Mhz and 200MHz.
So they tried to add 1ohm resistor (1005 size) between BTST and SW terminal like R2 in BQ25302 EVM to reduce EMI noise.

But BQ25302 couldn't operate correctly and LED which connected to STAT terminal was blinked to inform any fault happen then.

Do you know why the fault is happened?
If you need any more information, could you please let me know?

Your reply would be appreciated.

Best regards,
Kazuya.

over 2 years ago

0 Ning T over 2 years ago

TI__Guru 57701 points

Hi,

We will check and get back to you.

Thanks,

Ning.

0 Garrett Kreger over 2 years ago in reply to Ning T

TI__Mastermind 31720 points

Hi Kazuya,

Ning is out of office today please expect an update on this tomorrow.

Regards,

Garrett

0 Kazuya Nakai59 over 2 years ago in reply to Garrett Kreger

Guru 21595 points

Hi Garrett,

Thank you very much for your supports.

I'm looking forward to receiving your answer.

Thank you again and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

1. What were the device operating conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, PMID, IPMID when the STAT pin blinks?

2. Why the customer think the fault is related to the 1ohm resistor?

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Thank you very much for your reply.

My answers are the follows.
Ans1. VBUS=5V, VBAT=3.6V, IBAT=2A, PMID=5V, IVBUS and IPMID are unknown.
Ans2. The fault was happened when the 1ohm resistor was inserted between BTST terminal and boot capacitor.

Thank you again and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

What is the VBUS adaptor current limit?

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

They use 2.4A output current adaptor.

Thank you very much and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

Did the customer test multiple boards with 1ohm resistor?

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Yes, they tried at 2 chips and same result.

Do you have any idea why the fault was happened?

Thank you very much and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

Could they please try on the EVM? We do not observe the same behavior.

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Thank you very much for your strong support.

Do you mean that BQ25302 operated normally without any fault even though 1ohm resistor added in your evaluation?

Thank you again and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

Right. It works normally without fault.

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Thank you very much for your reply.

I see. I will check it on EVM.

Thank you again and best regards,
Kazuya.

0 Kazuya Nakai59 over 2 years ago in reply to Kazuya Nakai59

Guru 21595 points

Hello Ning,

Could I ask you the following question?

Q. When the device works normally in your evaluation, how was the device temperature? Was the device hot? Or it is not hot?
Because I thought that internal switching FET gate voltage transient becomes slower by 1ohm resistor inserting.

Also I thought, if it is hot, thermal shut may be asserted and the device fault is happen and LED is blinking then.

Your reply would be much helpful.

Thank you and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

Referring to Table 8-2. STAT Pin State on the d/s, the STAT pin may blink when the following happens. If the IC gets hot on the customer board and ICHG drops to 0A repetitively, it is likely to be thermal shutdown.

1. VBUS input over voltage

2. TS cold/hot faults

3. Battery over voltage

4. IC thermal shutdown

5. Safety timer expiration with battery voltage below recharge threshold

6. ICHG pin open or short

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Thank you very much for your reply.

In thermal shutdown case, does BQ25302 resume charging when the device temperature drops?

Thank you again and best regards,
Kazuya.

0 Ning T over 2 years ago in reply to Kazuya Nakai59

TI__Guru 57701 points

Kazuya,

The charger is reenabled when the junction temperature is 25°C below TSHUT. Please refer to 8.3.4.2 Thermal Regulation and Thermal Shutdown for the details.

Thanks,

Ning.

0 Kazuya Nakai59 over 2 years ago in reply to Ning T

Guru 21595 points

Hello Ning,

Thank you very much for your strong supports and I'm sorry to be late response.
Could I ask you an additional question?
Q. Didn't the BQ25302 get hot in your evaluation?

Thank you again and best regards,
Kazuya.

0 Garrett Kreger over 2 years ago in reply to Kazuya Nakai59

TI__Mastermind 31720 points

Hi Kazuya,

Ning is out of office today. She can comment on if she observed the BQ25302 get hot when she returns. Thank you for your patience.

Regards,

Garrett

0 Kazuya Nakai59 over 2 years ago in reply to Garrett Kreger

Guru 21595 points

Hi Garrett,

Thank you very much for your reply.
I see. I'm looking forward to receiving her comment.

Thank you again and best regards,
Kazuya.

0 Garrett Kreger over 2 years ago in reply to Kazuya Nakai59

TI__Mastermind 31720 points

Hi Kazuya,

Please allow me to further clarify. Ning is still out of office. Please expect a response early next week.

Regards,

Garrett

0 Ning T over 2 years ago in reply to Garrett Kreger

TI__Guru 57701 points

Kazuya.

Did you test on the EVM? Is there any concern?

Thanks,

Ning.

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BQ25302: Why is a fault happened when 1ohm register is connected to the capacitor between BTST and SW terminal in series?