BQ34Z100: Circuit design for multi-cell application

Shreya Agrawal

Part Number: BQ34Z100
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Tool/software:

Hi team,

I have a 64 cell lion battery pack. I am using BQ34Z100 to measure pack parameters. I have tested the same golden image file with the EV2400 EVM board for 48V, as well as on my own PCB. The golden image does not remain restored on our PCB when the power is cycled, but remains intact on the EVM even after power cycling the fuel gauge.

Basically, once I prepare an image file on one gauge, after a power cycle or on a new fuel gauge, I have to reflash the image and re-calibrate everything from scratch.

Kindly let me know if there are certain hardware design changes from the EVM design schematics, which need to be done for multi-cell applications.

I have been using this design as reference. -

TIDRY27B.ZIP

Regards,

Shreya

over 1 year ago

0 Diego over 1 year ago

TI__Mastermind 26255 points

Hi Shreya,

The voltage divider will need to be changed.

Here is some helpful documentation - bq34z100-G1 High Cell Count and High Capacity Applications

Regards,

Evan

0 Shreya Agrawal over 1 year ago in reply to Diego

Prodigy 240 points

Hi Evan,

I changed the resistor values in the divider. Apart form that are there any capacitances or resistors that need to be changed for REGIN or REG25 or for the shunt sensing circuitry?

Regards,

Shreya

0 Diego over 1 year ago in reply to Shreya Agrawal

TI__Mastermind 26255 points

Hi Shreya,

These should remain the same.

Regards,

Evan

0 Shreya Agrawal over 1 year ago in reply to Diego

Prodigy 240 points

Hi Evan,

So I am having issues of losing the flashed golden image file at times as I power cycle the fuel gauge on my custom PCB, but the same is not observed on the EVM. I presumed the issue was due to hardware changes for multi-cell applications. But since thats not the case as per the above discussion, can you suggest a reason for this?

Regards,

Shreya

0 Diego over 1 year ago in reply to Shreya Agrawal

TI__Mastermind 26255 points

Hi Shreya,

Is the voltage above the Flash Update ok Voltage?

Are you using BQstudio or an external MCU to communicate with the device?

Please write, reset, then read to verify parameters have updated

Regards,

Evan

0 Shreya Agrawal over 1 year ago in reply to Diego

Prodigy 240 points

Hi Evan,

Flash update ok voltage is way below my actual battery voltage and I am testing everything on BQStudio and will switch to my own MCU once all issues with BQStudio are sorted. Device VCC never falls below 3.2V in my case.

Regards,

Shreya

0 Shreya Agrawal over 1 year ago in reply to Shreya Agrawal

Prodigy 240 points

Hi Evan,

I have used 5megaohms as high side resistor and 16.5kohms as the low side resistor for my divider and my maximum battery voltage would be 268.8V. So I am writing a value of 4611 in the memory and programming it for total number of cells in my system.

Regards,

Shreya

0 Diego over 1 year ago in reply to Shreya Agrawal

TI__Mastermind 26255 points

Hi Shreya,

Correct me if I am wrong but, you are able to write to the device, it just loses the memory when a power cycle occurs. Once you write new values to the gauge can you read back those same values?

Regards,

Evan

Power management

Power management forum

BQ34Z100: Circuit design for multi-cell application