BQ40Z50-R2 Datasheet, PDF (25/51 Pages) Texas Instruments – 1-Series, 2-Series, 3-Series, and 4-Series Li-Ion Battery Pack Manager

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bq40z50-R2
SLUSCS4 – JUNE 2017
Feature Description (continued)
8.3.5.5 Cell Balancing
The device supports cell balancing by bypassing the current of each cell during charging or at rest. If the device's
internal bypass is used, up to 10 mA can be bypassed and multiple cells can be bypassed at the same time.
Higher cell balance current can be achieved by using an external cell balancing circuit. In external cell balancing
mode, only one cell at a time can be balanced.
The cell balancing algorithm determines the amount of charge needed to be bypassed to balance the capacity of
all cells.
8.3.6 Battery Parameter Measurements
8.3.6.1 Charge and Discharge Counting
The bq40z50-R2 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 SRP and SRN terminals. The integrating ADC measures
bipolar signals from –0.1 V to 0.1 V. The bq40z50-R2 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 bq40z50-R2 continuously integrates
the signal over time, using an internal counter. The fundamental rate of the counter is 0.26 nVh.
8.3.7 Battery Trip Point (BTP)
Required for WIN8 OS, the battery trip point (BTP) feature indicates when the RSOC of a battery pack has
depleted to a certain value set in a DF register. This feature enables a host to program two capacity-based
thresholds that govern the triggering of a BTP interrupt on the BTP_INT pin, and the setting or clearing of the
OperationStatus[BTP_INT] on the basis of RemainingCapacity().
An internal weak pullup is applied when the BTP feature is active. Depending on the system design, an external
pullup may be required to put on the BTP_INT pin. See PRES, BTP_INT, DISP for details.
8.3.8 Lifetime Data Logging Features
The bq40z50-R2 offers lifetime data logging for several critical battery parameters. The following parameters are
updated every 10 hours if a difference is detected between values in RAM and data flash:
• Maximum and Minimum Cell Voltages
• Maximum Delta Cell Voltage
• Maximum Charge Current
• Maximum Discharge Current
• Maximum Average Discharge Current
• Maximum Average Discharge Power
• Maximum and Minimum Cell Temperature
• Maximum Delta Cell Temperature
• Maximum and Minimum Internal Sensor Temperature
• Maximum FET Temperature
• Number of Safety Events Occurrences and the Last Cycle of the Occurrence
• Number of Valid Charge Termination and the Last Cycle of the Valid Charge Termination
• Number of Qmax and Ra Updates and the Last Cycle of the Qmax and Ra Updates
• Number of Shutdown Events
• Cell Balancing Time for Each Cell
(This data is updated every 2 hours if a difference is detected.)
• Total FW Runtime and Time Spent in Each Temperature Range
(This data is updated every 2 hours if a difference is detected.)
Copyright © 2017, Texas Instruments Incorporated
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