BQ34Z100-R2: MCU requirements to handle BQ34Z100-R2+BQ76972

SAERO

Part Number: BQ34Z100-R2
Other Parts Discussed in Thread: BQ76972, TIDA-010030, BQ7718, BQ76200, BQ34Z100, BQ40Z80

Tool/software:

Hello,
We are planning to use BQ34Z100-R2+BQ76972. Is MCU mandatory on BMS for this kind of setup to work? If yes, what are the tasks the MCU must handle? We want to choose low power MCUs for this and wondering what are the options that are available with CAN interface.

TIDA-010030 uses a external FET driver. Is it required for BQ76972? We are planning to skip using BQ76200 and BQ7718 from this. Is that okay?

Thank you!

1 month ago

0 Diego 1 month ago

TI__Genius 14810 points

Hi,

An MCU is required to configure the gauge. The MCU is not needed for gauge the SOC of the battery. The BQ34z100 does not support CAN communication.

I am unfamiliar with the BQ76972, I will assign this thread to someone from the mointor team to answer that questions.

Regards,

Evan

0 SAERO 1 month ago in reply to Diego

Prodigy 226 points

Diego said:
An MCU is required to configure the gauge. The MCU is not needed for gauge the SOC of the battery. The BQ34z100 does not support CAN communication.

Can only BQ34Z100 I2C be used as main interface for communication? I think the BQ76972 needs OTP done for this?
Possible to elaborate on what configurations MCU needs to handle?

0 Maxwell Verboncoeur 1 month ago in reply to SAERO

TI__Genius 17970 points

Hi,

The BQ76972 can operate as a standalone monitor and protector and does have integrated high side FET drivers. The only caveat to this is that you will need to write the OTP of the BQ76972 on the production line to allow it to act in standalone mode with the settings that you want. An MCU to configure the BQ76972's settings on startup is the typical solution that we see.

I'll let the gauge team comment on the BQ34Z100's capabilities.

Regards,

Max Verboncoeur

0 SAERO 1 month ago in reply to Maxwell Verboncoeur

Prodigy 226 points

Maxwell Verboncoeur said:
An MCU to configure the BQ76972's settings on startup

What is considered as startup? WAKE from shutdown mode or sleep? I assume AFE will keep monitoring in sleep?
Thank you!

0 Maxwell Verboncoeur 1 month ago in reply to SAERO

TI__Genius 17970 points

Hi,

Any wake from shutdown mode is considered startup. Correct, the AFE continues to monitor at a lower rate during sleep mode to reduce power consumption.

Regards,

Max Verboncoeur

0 Diego 1 month ago in reply to Maxwell Verboncoeur

TI__Genius 14810 points

Hi,

Regarding the BQ34z100, You can communicate with this gauge via I2C or HDQ.

Regards,

Evan

0 SAERO 1 month ago in reply to Diego

Prodigy 226 points

Hi,

How about cell data? Is there a way to get cell data directly via BQ34Z100?

0 SAERO 1 month ago in reply to Maxwell Verboncoeur

Prodigy 226 points

Hey,
The difference between BQ7697202PFBR and BQ76972PFBR is just software functions or REG and CRC is not available at all for BQ76972PFBR?
Only BQ76972PFBR is available in stock for ordering. Wanted to confirm.

0 Diego 1 month ago in reply to SAERO

TI__Genius 14810 points

Hi,

The BQ34z100 does is a top of stack gauge and does not monitor individual cells, this may be possible with the monitor.

I will let the monitor comment on the BQ7697202.

Regards,

Diego

0 Maxwell Verboncoeur 1 month ago in reply to SAERO

TI__Genius 17970 points

Hi,

The difference between these two part numbers is the default settings listed below. They are identical ICs otherwise.

Both parts are able to be configured to use I2C/SPI or CRC or the REGs, the difference is that the two devices have different initial configurations.

Regards,

Max Verboncoeur

0 SAERO 1 month ago in reply to Diego

Prodigy 226 points

Can both devices be used on same I2C bus? And pick data as required?

0 Maxwell Verboncoeur 1 month ago in reply to SAERO

TI__Genius 17970 points

Hi,

If the I2C addresses are different then they can be used on the same bus. The BQ76972's default 7-bit address is 0x08, and I'm not certain what the gauge's default address is, but the BQ76972 can be OTP'ed with a new I2C address if there is any overlap.

Regards,

Max Verboncoeur

0 SAERO 6 days ago in reply to Maxwell Verboncoeur

Prodigy 226 points

Hello, Does BQ34Z100-R2 need any data from AFE for accurate SoC estimation? Or does it work completely standalone?
Will BQ34Z100-R2 be accurate without cell data?

Thank You!

0 Diego 6 days ago in reply to SAERO

TI__Genius 14810 points

Hi,

No, the BQ34z100 does not need any data from the AFE. However, it is very important that the cells are balanced to accurately estimate SOC.

The BQ34z100 only needs accurate voltage, current, and temperature readings from the pack. I recommend viewing the evm schematic.

bq34z100EVM Wide Range Impedance Track Enabled Battery Fuel Gauge (Rev. B) (ti.com)

Regards,

Diego

0 SAERO 5 days ago in reply to Diego

Prodigy 226 points

Hello,

Will it be as accurate as BQ40Z80 (6 cells) which takes cell resistance as factor to estimate SoC? I remember reading about BQ40Z80 uses lot of cell parameters in SoC estimation. Will accuracy be affected on BQ34Z100 because of not having cell data?

Thanks.

0 Diego 3 days ago in reply to SAERO

TI__Genius 14810 points

Hi,

In general top of stack gauges have less resolution than gauges that monitor individual cells, however it is possible to achieve the same accuracy.

Regards,

Diego

0 SAERO 2 days ago in reply to Diego

Prodigy 226 points

What's the accuracy difference that we can expect from BQ40Z80 and BQ34Z100?

0 Diego 2 days ago in reply to SAERO

TI__Genius 14810 points

Hi,

Difficult to answer, if accuracy is a high concern I recommend 40z80.

What does an expected load from your application look like?

Regards,

Diego

0 SAERO 1 day ago in reply to Diego

Prodigy 226 points

We are designing for 12S battery pack with 60A continuous current.

0 Diego 11 hours ago in reply to SAERO

TI__Genius 14810 points

Hi,

The only gauge we have that supports 12S applications is BQ34z100-R2.

Regards,

Diego

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BQ34Z100-R2: MCU requirements to handle BQ34Z100-R2+BQ76972