BQ40Z50-R2: PTC temperature wrong value in GUI

DudeFromRiga

Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

Hi,
We're in process of R&D of new project, containing BQ40z50 IC. We already managed to launch communication with the board.

We have noticed, that PTC thermistor, which is placed near FETs, always show the same temperature in GUI (bqStudio), even when it's cooled or heated. We use PRF15BE103RB6RC PTC .

Why this happen / how can we fix this?

over 7 years ago

0 Swaminathan Ramanathan75031 over 7 years ago

TI__Expert 6575 points

The bq40z50 only supports NTC thermistor (10kOhms at 25degC) for temperature measurement (Section 9.2.2.3.4 of the data sheet).
A PTC thermistor can be used for thermal protection (Safety PTC Thermistor Section 9.2.2.3.6 of the data sheet), but this temperature is only used for safety and the actual temperature is not measured by the gauge using this thermistor.
Regards,
Swami

0 DudeFromRiga over 7 years ago in reply to Swaminathan Ramanathan75031

Intellectual 305 points

Thank You!
I believe then it's some bug in GUI, because "FET temperature" field there have value in Celsius degrees. Moreover, I noticed that it changes, depending on 4x NTC thermistor temperature.

0 Swaminathan Ramanathan75031 over 7 years ago in reply to DudeFromRiga

TI__Expert 6575 points

Hi,
Please check that the "Temperature Enable" and "Temperature Mode" settings are set correctly for the Cell and FET temperatures.
Also the default coefficients for the thermistors are based on the Semitec 103AT.
If you have a different NTC for the temperature measurement, the coefficients need to be re-calculated.
The explanation and calculator are available at www.ti.com/.../slua398 and www.ti.com/.../slua398
Regards,
Swami

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BQ40Z50-R2: PTC temperature wrong value in GUI