BQ34Z950 Datasheet, PDF (15/28 Pages) Texas Instruments – SBS 1.1-COMPLIANT GAS GAUGE AND PROTECTION ENABLED WITH IMPEDANCE TRACK WITH OPTIONAL DQ INTERFACE

bq34z950
www.ti.com
SLUSBF0A – APRIL 2013 – REVISED MAY 2013
• In SLEEP mode, the bq34z950 performs measurements, calculations, protection decisions, and data updates
in adjustable time intervals. Between these intervals, the bq34z950 is in a reduced power state. The
bq34z950 has a wake function that enables exit from SLEEP mode when current flow or failure is detected.
• In SHUTDOWN mode, the bq34z950 is completely disabled.
CONFIGURATION
Oscillator Function
The bq34z950 fully integrates the system oscillators. Therefore, the bq34z950 requires no external components
for this feature.
BATTERY PARAMETER MEASUREMENTS
The bq34z950 uses an integrating delta-sigma analog-to-digital converter (ADC) for current measurement, and a
second delta-sigma ADC for individual cell and battery voltage and temperature measurement.
Charge and Discharge Counting
The integrating delta-sigma ADC measures the charge/discharge flow of the battery by measuring the voltage
drop across a small-value sense resistor between the SRP and SRN pins. The integrating ADC measures bipolar
signals from –0.25 V to 0.25 V. The bq34z950 detects charge activity when V_SR = V_(SRP) – V_(SRN) is positive, and
discharge activity when V_SR = V_(SRP) – V_(SRN) is negative. The bq34z950 continuously integrates the signal over
time, using an internal counter. The fundamental rate of the counter is 0.65 nV/h.
Voltage
The bq34z950 updates the individual series cell voltages at 1-s intervals. The internal ADC of the bq34z950
measures the voltage, and scales and calibrates it appropriately. This data is also used to calculate the
impedance of the cell for the Impedance Track gas gauging.
Current
The bq34z950 uses the GSRP and GSRN inputs to measure and calculate the battery charge and discharge
current using a 5-mΩ to 20-mΩ typical sense resistor.
Auto Calibration
The bq34z950 provides an autocalibration feature to cancel the voltage offset error across SRP and SRN for
maximum charge measurement accuracy. The bq34z950 performs autocalibration when the SMBus and DQ
lines stay low for a minimum of 16 s, and the DF:AutoCal_PerSleep counter has counted up to its programmed
value. The AutoCal_PerSleep counter provides a way for the user to specify the number of times the part can
enter SLEEP mode before an offset calibration is performed. This is to prohibit unnecessary calibration cycles for
battery packs that enter SLEEP mode frequently. The bq34z950 is capable of automatic offset calibration down
to 1 μV.
Temperature
The bq34z950 has an internal temperature sensor and external temperature sensor input, TS1, which can be
used to sense the environmental temperature of the batteries. The bq34z950 can be configured to use internal or
external temperature sensors. The external sensor input is used in conjunction with an NTC thermistor (default is
Semitec 103AT).
COMMUNICATIONS
The bq34z950 uses SMBus v1.1 with MASTER mode and package error checking (PEC) options per the SBS
specification. Integrated error checking is not available on the DQ interface.
SMBus/DQ On and Off States
The bq34z950 detects an SMBus/DQ off state when SMBC, SMBD, and DQ are logic-low for ≥ 2 seconds.
Clearing this state requires either SMBC or SMBD or DQ to transition high. Within 1 ms, the communication bus
is available.
Copyright © 2013, Texas Instruments Incorporated
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