Texas Instruments BQ76942, Manual

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10.10 Current Calibration
The BQ76942 device coulomb counter ADC measures the differential voltage between the SRP and SRN pins
to calculate the system current. The device includes the optional capability for the customer to calibrate the
coulomb counter offset and current gain on the production line.
The Calibration:Current Offset:CC Offset configuration register contains an offset value in units of 32-bit
coulomb counter ADC counts / Calibration:Current Offset:Coulomb Counter Offset Samples . The value of
Calibration:Current Offset:CC Offset / Calibration:Current Offset:Coulomb Counter Offset Samples is
subtracted from the raw coulomb counter ADC counts, then the result is multiplied by Calibration:Current:CC
Gain and scaled to provide the final result in units of userA.
The BQ76942 device uses the Calibration:Current:CC Gain and Calibration:Current:Capacity Gain
configuration values to convert from the ADC value to current. The CC Gain reflects the value of the sense
resistor used in the system, while the Capacity Gain is simply the CC Gain multiplied by 298261.6178.
The CC Gain and Capacity Gain are encoded using a 32-bit IEEE-754 floating point format. The effective value
of the sense resistor is given by:
CC Gain = 7.4768 / (Rsense in mΩ)
10.11 Temperature Calibration
The BQ76942 device enables the customer to calibrate the internal as well as external temperature
measurements on the production line, by storing an offset value that is added to the calculated measurement
before reporting. A separate offset for each temperature measurement can be stored in the configuration
registers shown below.
Table 10-1. Temperature Calibration Settings
Section Subsection Register Description Comment Units
Calibration Temperature Internal Temp Offset 0.1 K
Calibration Temperature CFETOFF Temp Offset CFETOFF pin thermistor 0.1 K
Calibration Temperature DFETOFF Temp Offset DFETOFF pin thermistor 0.1 K
Calibration Temperature ALERT Temp Offset ALERT pin thermistor 0.1 K
Calibration Temperature TS1 Temp Offset TS1 pin thermistor 0.1 K
Calibration Temperature TS2 Temp Offset TS2 pin thermistor 0.1 K
Calibration Temperature TS3 Temp Offset TS3 pin thermistor 0.1 K
Calibration Temperature HDQ Temp Offset HDQ pin thermistor 0.1 K
Calibration Temperature DCHG Temp Offset DCHG pin thermistor 0.1 K
Calibration Temperature DDSG Temp Offset DDSG pin thermistor 0.1 K
11 Primary and Secondary Protection Subsystems
11.1 Protections Overview
An extensive protection subsystem is integrated within the BQ76942 device, which can monitor a variety of
parameters, initiate protective actions, and autonomously recover based on conditions. The device also includes
a wide range of flexibility, such that the device can be configured to monitor and initiate protective action,
but with recovery controlled by the host processor, or such that the device only monitors and alerts the host
processor whenever conditions warrant protective action, but with action and recovery fully controlled by the host
processor.
The primary protection subsystem includes a suite of individual protections that can be individually enabled and
configured, including cell undervoltage and overvoltage, overcurrent in charge, three separate overcurrent in
discharge protections, short circuit current in discharge, cell overtemperature and undertemperature in charge
and discharge, FET overtemperature, a host processor communication watchdog timeout, and PRECHARGE
mode timeout. The cell undervoltage and overvoltage, overcurrent in charge, overcurrent in discharge 1 and 2,
BQ76942
SLUSE14B – DECEMBER 2020 – REVISED DECEMBER 2021
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