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communications interface. This internal temperature measurement can be used for cell or FET temperature
protections and logic based on configuration settings.
10.6 Thermistor Temperature Measurement
The BQ76952 device includes an on-chip temperature measurement and can also support up to nine external
thermistors on multifunction pins (TS1, TS2, TS3, CFETOFF, DFETOFF, ALERT, HDQ, DCHG, and DDSG). The
device includes an internal pullup resistor to bias a thermistor during measurement.
The internal pullup resistor has two options which can set the pullup resistor to either 18-kΩ or 180-kΩ (or none
at all). The 18-kΩ option is intended for use with thermistors such as the Semitec 103-AT, which has 10-kΩ
resistance at room temperature. The 180-kΩ is intended for use with higher resistance thermistors such as
the Semitec 204AP-2, which has 200-kΩ resistance at room temperature. The resistor values are measured
during factory production and stored within the device for use during temperature calculation. The individual pin
configuration registers determine which pin is used for a thermistor measurement, what value of pullup resistor is
used, as well as whether the thermistor measurement is used for a cell or FET temperature reading.
To provide a high precision temperature result, the device uses the same 1.8 V LDO voltage for the ADC
reference as is used for biasing the thermistor pullup resistor, thereby implementing a ratiometric measurement
that removes the error contribution from the LDO voltage level. The device processes the digitized thermistor
voltage to calculate the temperature based on multiorder polynomials, which can be programmed by the user
based on the specific thermistor selected.
10.7 Factory Trim of Voltage ADC
The BQ76952 device includes factory trim for the cell voltage ADC measurements in order to optimize the
voltage measurement performance even if no further calibration is performed by the customer. Calibration can
be performed by the customer on the production line to further optimize the performance in the system. The
trim information is used to correct the raw ADC readings before they are reported as 16-bit voltage values. The
32-bit ADC voltage data, which is generated in units of ADC counts, is modified before reporting by subtracting
a stored offset trim value. The resulting reported data does not include any further correction (such as for gain),
therefore the customer will need to process them before use.
Copyright © 2021 Texas Instruments Incorporated
REG18 (§1.8V)
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Figure 10-3. External Thermistor Biasing
Product Folder Links:
SLUSE13A – JANUARY 2020 – REVISED MAY 2021
VREF1
reference
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Voltage
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BQ76952
BQ76952
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