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interface and either triggers an action, or provides a data value to be written to the device, or instructs the device
to report data back to the host. Subcommands are additional commands that are accessed indirectly using the
7-bit command address space and provide the capability for block data transfers. For more information on the
commands and subcommands supported by the device, refer to
7.3.2 Configuration Using OTP or Registers
The BQ76907 device includes registers, with values stored in the RAM, and can be loaded automatically from
one-time programmable (OTP) memory. At initial power-up, the device loads OTP settings into registers, which
are used by the device during operation. The OTP settings are programmed into the device by TI during
manufacturing. Register values are preserved while the device is in NORMAL, SLEEP, or DEEPSLEEP modes.
If the device enters SHUTDOWN mode, all register memory is cleared, and the device reloads values from OTP
when powered again.
7.3.3 Device Security
The BQ76907 device includes two security modes: SEALED and FULLACCESS, which can be used to limit the
ability to view or change settings.
•
In SEALED mode, most data and status can be read using commands and subcommands, but only selected
settings can be changed. Data memory settings cannot be changed directly.
•
FULLACCESS mode allows the capability to read and modify all device settings.
Selected settings in the device can be modified while the device is in operation through supported commands
and subcommands, but in order to modify all settings, the device must enter CONFIG_UPDATE mode (see
CONFIG_UPDATE
Mode), which stops the device operation while settings are being updated. After the update
is completed, the operation is restarted using the new settings. CONFIG_UPDATE mode is only available in
FULLACCESS mode.
The BQ76907 device implements a key-access scheme to transition between SEALED and FULLACCESS
modes. Changing from SEALED to FULLACCESS requires that a unique set of keys be sent to the device
through subcommands. Refer to
7.4 Device Hardware Features
7.4.1 Voltage ADC
The BQ76907 integrates a delta-sigma voltage ADC that is multiplexed between measurements of cell voltages,
an internal temperature sensor, an external thermistor, as well as performs measurements of the voltage at
the VC7 pin, the internal 1.8-V LDO voltage, and the VSS rail (the latter two are for diagnostic purposes).
The BQ76907 device supports measurements of individual differential cell voltages in a series configuration,
ranging from 2-series cells to 7-series cells. Each cell voltage measurement is a differential measurement of
the voltage between two adjacent cell input pins, such as VC1–VC0, VC2–VC1, and so forth. The cell voltage
measurements are processed based on trim and calibration corrections and then reported in a 16-bit resolution
using units of 1 mV.
The ADC takes its input from the ADC multiplexer and generates a high-speed digital data stream which is
digitally filtered to produce a 24-bit output. The ADC uses the 262.144-kHz LFO clock as its sampling clock. The
digital filter includes programmable decimation rates, which result in data generated at different intervals and
with differing resolutions. The effective resolution (defined as the resolution such that the data exhibits 1-sigma
variation with ±1 LSB) of the ADC conversions changes as the decimation rate changes, with effective resolution
increasing as the output rate is reduced.
7.4.2 Coulomb Counter and Digital Filters
The BQ76907 device monitors pack current using a low-side sense resistor that connects to the SRP and SRN
pins through an external RC filter, which should be connected such that a charging current will create a positive
voltage on SRP relative to SRN. The differential voltage between SRP and SRN is digitized by an integrated
delta-sigma coulomb counter ADC, which can digitize voltages over a ±200 mV range and uses multiple digital
Copyright © 2023 Texas Instruments Incorporated
BQ76907 Technical Reference Manual
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BQ76907
BQ76907
SLUSE96 – NOVEMBER 2023
Manual.
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