BQ3055 Datasheet, PDF (17/23 Pages) Texas Instruments – 2-Series, 3-Series, and 4-Series Li-Ion Battery Pack Manager

bq3055
www.ti.com
SLUSA91A – OCTOBER 2010 – REVISED JANUARY 2012
BATTERY PARAMETER MEASUREMENTS
Charge and Discharge Counting
The bq3055 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.
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 SR1 and SR2 pins. The integrating ADC measures bipolar
signals from –0.25 V to 0.25 V. The bq3055 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 bq3055 continuously integrates the signal over
time, using an internal counter. The fundamental rate of the counter is 0.65 nVh.
Voltage
The bq3055 updates the individual series cell voltages at 0.25-second intervals. The internal ADC of the bq3055
measures the voltage, and scales and calibrates it appropriately. This data is also used to calculate the
impedance of the cell for the CEDV gas-gauging.
Current
The bq3055 uses the SRP and SRN inputs to measure and calculate the battery charge and discharge current
using a 5-mΩ to 20-mΩ typ. sense resistor.
Auto Calibration
The bq3055 provides an auto-calibration feature to cancel the voltage offset error across SRN and SRP for
maximum charge measurement accuracy. The bq3055 performs auto-calibration when the SMBus lines stay low
continuously for a minimum of 5 s.
Temperature
The bq3055 has an internal temperature sensor and inputs for two external temperature sensors. All three
temperature sensor options are individually enabled and configured for cell or FET temperature. Two
configurable thermistor models are provided to allow the monitoring of cell temperature in addition to FET
temperature, which may be of a higher temperature type.
Communications
The bq3055 uses SMBus v1.1 with Master Mode and packet error checking (PEC) options per the SBS
specification.
SMBus On and Off State
The bq3055 detects an SMBus off state when SMBC and SMBD are low for two or more seconds. Clearing this
state requires that either SMBC or SMBD transition high. The communication bus will resume activity within 1
ms.
SBS Commands
See the bq3055 Technical Reference Manual (SLUU440) for further details.
Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Link(s): bq3055
Submit Documentation Feedback
17