BQ40z50 short circuit protection settings

Roman Fedirko

Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

Hello,

I was testing battery gauge bq40z50 with 4 series cells. I noticed that after short circuit pack voltage is not coming back.

I checked with specification and ASCCL and ASCDL are not set (see attachments). Any idea how to get the pack

voltage back after short circuit event on PACK terminals?

Thank you in advance!

Roman

over 10 years ago

0 ThomasCosby over 10 years ago

TI__Guru 73830 points

Roman,
Are you saying that there is no pack voltage with the screenshot provided? The flags do not indicate that there are any problems. Are you using the bq40z50EVM?
Tom

0 Roman Fedirko over 10 years ago in reply to ThomasCosby

Prodigy 140 points

Hi Tom,

I'm working with custom battery pack based on that chip. I'll try with evaluation board as well.
I agree that is strange why pack voltage is missing...

/Roman

0 Roman Fedirko over 10 years ago in reply to Roman Fedirko

Prodigy 140 points

Hello again,

I tested with EVB and the PACK voltage is resumed after applying charging voltage.
I used the same FW as in custom battery pack. Do you know what can be an issue?

Thank you for help!
Roman

0 ThomasCosby over 10 years ago in reply to Roman Fedirko

TI__Guru 73830 points

I would check the voltage at the Pack pin on the device to confirm that it is present. Sometime bqStudio loses sync with the device, so I would try restarting the program.

0 Roman Fedirko over 10 years ago in reply to ThomasCosby

Prodigy 140 points

I measured with multimeter there is no pack voltage...

When I'm charging custom pack I can see charging current so the charging FET is enabled. The problem is with discharging FET that
seems to be disabled but bqStudio shows that is enabled.

0 ThomasCosby over 10 years ago in reply to Roman Fedirko

TI__Guru 73830 points

Roman,
I would compare the schematic for your module to the TI EVM and make sure that they are the same. Other than that, there may be a defective component.

Tom

0 Roman Fedirko over 10 years ago in reply to ThomasCosby

Prodigy 140 points

Hi Thomas,

I checked again all the registers and seems that XDSG flag is set after short circuit event.
I noticed that voltage returns when I set NR flag to 1.

That is quite strange why is not resuming without NR flag. I have 10k pulldown to SYSPRES and I2C pullups.
Do you have any ideas?

How about NR settings? If I have laptop computer with replaceable battery I understand that NR shall be set to 0?

Regards,
Roman

0 ThomasCosby over 10 years ago in reply to Roman Fedirko

TI__Guru 73830 points

Roman,

The recovery from an SCD event is different depending on the NR configuration. Did you check the table on page 16 of the TRM?

Tom

0 Roman Fedirko over 10 years ago in reply to ThomasCosby

Prodigy 140 points

Hi Tom,

I just checked that. It says Low-high-low transition on PRES pin.
Is that mean I need to reinsert the pack?

/Roman

0 ThomasCosby over 10 years ago in reply to Roman Fedirko

TI__Guru 73830 points

You said that you have a 10 kohm pull down resistor on SYSPRES, so the pin should not transition low-high-low when the pack is removed. This pack is setup as a non removable pack, so you will need to set the NR=1 to recover. You could also removed the 10 kohm resistor and pull the SYSPRES pin low through the connector to configure the pack as a removable pack.

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BQ40z50 short circuit protection settings