BQ40Z60_16 Datasheet, PDF (26/47 Pages) Texas Instruments – Programmable Battery Management Unit

bq40z60
SLUSAW3C – DECEMBER 2014 – REVISED JULY 2015
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Feature Description (continued)
The system can still provide load current from the battery pack if the adaptor current cannot support the system
load. The diode of the CHG FET starts to conduct as the system voltage decreases to a point where the pack
voltage is greater than the system regulation voltage – V_diode. If the average discharge current is high, the system
can turn ON the CHG FET for improved efficiency and minimized line losses during the discharge phase.
9.3.4 Fuel Gauge and Control Details
The bq40z60 uses the Impedance Track™ algorithm to measure and calculate the available capacity in battery
cells. The bq40z60 accumulates a measure of charge and discharge currents and compensates the charge
current measurement for the temperature and state-of-charge of the battery. The bq40z60 estimates self-
discharge of the battery and also adjusts the self-discharge estimation based on temperature. The device also
has TURBO BOOST mode support, which enables the bq40z60 to provide the necessary data for the MCU to
determine what level of peak power consumption can be applied without causing a system reset or a transient
battery voltage level spike to trigger termination flags. See the bq40z60 Technical Reference Manual (SLUUA04)
for further details.
9.3.4.1 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 allows a host to program two capacity-based
thresholds that govern triggering a BTP interrupt on the BTP_INT pin, and setting or clearing 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 High-Voltage General Purpose I/O (ALERT, SYSPRES)
for details.
9.3.4.2 Lifetime Data Logging Features
The bq40z60 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.)
9.3.5 Authentication
The bq40z60 supports authentication by the host using SHA-1. More information about the algorithm can be
found in the bq40z60 Technical Reference Manual (SLUUA04).
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