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performance even if no further calibration is performed by the customer. The trim information is used to correct
the raw ADC readings before they are reported as 16-bit values after processing. The current measurement
trim is performed to provide units of mA assuming a 1-mΩ external sense resistor is used, although this can
be modified by the user if different units are desired. The trimmed offset and gain values can be modified by
the user in order to perform calibration on the customer production line, to further optimize performance in the
system. For further details, see the
7.6 Protection Subsystem
7.6.1 Protections Overview
The BQ76907 integrates an extensive primary protection subsystem 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 protection subsystem includes a suite of individual protections which can be individually enabled and
configured, including cell undervoltage and overvoltage, overcurrent in charge, two separate overcurrent in
discharge protections, short circuit current in discharge, cell overtemperature and undertemperature in charge
and discharge, internal die overtemperature, and a host processor communication watchdog timeout. The
overcurrent in charge and discharge and short circuit in discharge protections are based on comparator
decisions, while the remaining protections (such as those involving cell voltage, temperature, and host
watchdog) are based on ADC measurement or logic operation. The device integrates NFET drivers for low-side
CHG and DSG protection FETs, which can be configured in a series or parallel configuration, and can also be
used in pulse-width modulation mode to manually implement precharge or predischarge functionality.
7.6.2 Primary Protections
The BQ76907 integrates a broad suite of protections for battery management and provides the capability to
enable individual protections, as well as to select which protections will result in autonomous control of the FETs.
See the
BQ76907 Technical Reference Manual
protection features include:
•
Cell Undervoltage Protection
•
Cell Overvoltage Protection
•
Cell Open Wire Protection
•
Overcurrent in Charge Protection
•
Overcurrent in Discharge Protection (two tiers)
•
Short Circuit in Discharge Protection
•
Current Protection Latch
•
Undertemperature in Charge Protection
•
Undertemperature in Discharge Protection
•
Overtemperature in Charge Protection
•
Overtemperature in Discharge Protection
•
Internal Overtemperature Protection
•
Host Watchdog Fault Protection
The device also includes additional diagnostic checks which can also result in autonomous control of the FETs,
depending on configuration settings.
7.6.3 CHG Detector
The BQ76907 provides a signal that indicates if the CHG pin voltage is above a level of approximately 2 V. The
raw value of this flag can be read through the communications interface, and an alarm can be generated on the
ALERT pin whenever the debounced version of this flag changes state, based on device settings. This flag can
be used by the system to assist in recovery from a current fault condition.
Copyright © 2023 Texas Instruments Incorporated
BQ76907 Technical Reference
for detailed descriptions of each protection function. The primary
Product Folder Links:
Manual.
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