BQ76952EVM: Query regarding BQ76952EVM voltage calibration

jeet panchal

Part Number: BQ76952EVM
Other Parts Discussed in Thread: BQSTUDIO, , BQ76952

Hello,

I am working on BQ76952EVM launchpad and BQstudio. I would like to know how to calibrate cell voltage, pack voltage, stack voltage, LD pin and Current gain.

Does BQstudio helps in knowing the ADC counts of the voltage and current measurement registers?

I am using a 10k NTC thermistor for cell temperature measurement. So, which temperature model (18k temp model or 180k temp model or custom temperature model) will be required to measure temperature accurately.

over 4 years ago

0 Matt Sunna over 4 years ago

TI__Guru* 81034 points

Hi Jeet,

The EVM User Guide shows how to use the Calibration tool in BQStudio.https://www.ti.com/lit/pdf/sluuc33

There is also a Calibration document if you want to know all of the details for how the calibration works and how to use it in production. In BQStudio, it does not show all of the details for the calibration steps. https://www.ti.com/lit/pdf/sluaa32

The 18k temp model should be used. I am attaching a tool to calculate the thermistor coefficients - you just need to update the temperature resistance table to get the coefficients for your thermistor.

/cfs-file/__key/communityserver-discussions-components-files/196/bq769x2-Family-Thermistor-Coef-Calculator.xlsx

This video series has a video for using the EVM with BQStudio that may be helpful: https://training.ti.com/training-series-bq76952-bq76942-3-16s-3-10s-battery-monitors

By the way, the BQ76952 has now fully released to production. You might have the pre-production version in hand, so you can now order the final version of the device if needed.

Best regards,

Matt

0 jeet panchal over 4 years ago in reply to Matt Sunna

Intellectual 500 points

So if BQstudio calibrates cells in its own sequence we need not go through the command sequence to calibrate cell right?

0 Matt Sunna over 4 years ago in reply to jeet panchal

TI__Guru* 81034 points

Hi Jeet,

Yes, there is no need to use the Command Sequence window if you are using BQStudio. Use the Calibration window and follow the instructions in the EVM User Guide.

Best regards,

Matt

0 jeet panchal over 4 years ago in reply to Matt Sunna

Intellectual 500 points

Hey Matt thank you for clearing my doubts.

May I know why are there two different mosfet/switches for charging and discharging purpose. Rather both mosfets are placed in series to each other so with one mosfet the application can be performed right?

0 Matt Sunna over 4 years ago in reply to jeet panchal

TI__Guru* 81034 points

Hi Jeet,

This is the common practice in battery electronics. Each MOSFET has a body diode that allows it to conduct in one direction and the body diodes for the CHG and DSG FETs will face in the opposite direction. So when charging is disabled (maybe due to an over-voltage condition), discharging can still occur while charging is stopped.

There is also a body diode protection feature on this device to prevent the FET from damage when current is flowing through the body diode. You can read more about this feature in the device Technical Reference Manual: https://www.ti.com/lit/pdf/sluuby2

Best regards,

Matt

0 jeet panchal over 4 years ago in reply to Matt Sunna

Intellectual 500 points

Hey Matt,

It looks like I am little confused with charging and discharging pattern. Can you help me out with a drawing specifying the way charging will happen and similarly how discharging will happen. It looks like the charging and discharging falls on the same line with the help of two N-fet mosfet.

0 Matt Sunna over 4 years ago in reply to jeet panchal

TI__Guru* 81034 points

Hi Jeet,

This article explains it in a little more detail: https://electronics.stackexchange.com/questions/277248/lithium-battery-protection-circuit-why-are-there-two-mosfets-in-series-revers

I hope this helps,

Matt

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BQ76952EVM: Query regarding BQ76952EVM voltage calibration