BQ76925 Datasheet, PDF (1/29 Pages) Texas Instruments – Host Controlled Analog Front End for 3 to 6 Series Cell Lithium-Ion/ Polymer Battery

bq76925
www.ti.com
SLUSAM9A – JULY 2011 – REVISED JULY 2011
Host Controlled Analog Front End for 3 to 6 Series Cell Lithium-Ion/ Polymer Battery
Protection and Gas Gauging Applications
Check for Samples: bq76925
FEATURES
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• Analog Interface for Host cell Measurement
– Cell Input MUX, Level Shifter and Scaler
– 1.5 / 3.0 V Low-Drift, Calibrated Reference
Allows Accurate Analog to Digital
Conversions
• Analog Interface for Host Current
Measurement
– Variable Gain Current Sense Amplifier
Capable of Operation with 1 mΩ Sense
Resistor
• Switchable Thermistor Bias output for Host
Temperature Measurements
• Overcurrent Comparator with Dynamically
Adjustable Threshold
– Alerts Host to Potential Overcurrent Faults
– May be used to Wake up Host on Load
Connect
• Integrated Cell Balancing FETs
– Individual Host Control
– 50 mA per-cell Balancing Current
• Supports Cell Sense-line Open Wire Detection
• Integrated 3.3 V Regulator for Powering
Micro-controller and/or LEDs
• I²C Interface for Host Communications
– Optional Packet CRC for Robust Operation
• Supply Voltage Range From 4.2 to 26.4 V
• Low Power Consumption
– 40 µA Typical in Normal Mode
– 1.5 µA Maximum in Sleep Mode
• 20-pin TSSOP or 24-pin QFN Package
APPLICATIONS
• Primary Protection in Li-Ion Battery Packs
– Cordless Power Tools
– Light Electric Vehicles (E-Bike, Scooter,
etc.)
– UPS Systems
– Medical Equipment
– Portable Test Equipment
DESCRIPTION
The bq76925 Host controlled analog front end (AFE)
is part of a complete pack monitoring, balancing and
protection system for 3, 4, 5 or 6 series cell Lithium
batteries. The bq76925 allows a Host controller to
easily monitor individual cell voltages, pack current
and temperature. This information may be used by
the Host to determine unsafe or faulty operating
conditions such as over-voltage, under-voltage,
over-temperature and over-current, as well as cell
imbalance, state of charge and state of health
conditions.
Cell input voltages are level shifted, multiplexed,
scaled and output for measurement by a Host ADC.
A low-drift calibrated reference voltage is provided on
a dedicated pin to enable accurate measurements.
The voltage across an external sense resistor is
amplified and output to a Host ADC for both charge
and discharge current measurements. Two gain
settings enable operation with a variety of sense
resistor values over a wide range of pack currents.
To enable temperature measurements by the Host,
the AFE provides a separate output pin for biasing an
external thermistor network. This output can be
switched on and off under Host control to minimize
power consumption.
The bq76925 includes a comparator with a
dynamically selectable threshold for monitoring
current. The comparator result is driven through an
open-drain output to alert the host when the threshold
is exceeded. This feature can be used to wake up the
Host on connection of the load, or to alert the Host to
a potential fault condition.
The bq76925 integrates cell balancing FETs that are
fully controlled by the Host. The balancing current is
set by external resistors up to a maximum value of 50
mA. These same FETs may be utilized in conjunction
with cell voltage measurements to detect an open
wire on a cell sense-line.
The Host communicates with the AFE via an I²C
interface. A packet CRC may optionally be used to
ensure robust operation. The device may be put into
a low-current sleep mode via the I²C interface and
awakened by pulling up the ALERT pin.
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Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
UNLESS OTHERWISE NOTED this document contains
PRODUCTION DATA information current as of publication date.
Products conform to specifications per the terms of Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011, Texas Instruments Incorporated