BQ27750 Datasheet, PDF (19/34 Pages) Texas Instruments – Impedance Track Battery Gas Gauge and Protection Solution for 1-Series Cell Li-Ion Battery Packs

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bq27750
SLUSCM7 – JUNE 2017
Feature Description (continued)
7.3.19 Short-Circuit Current in Discharge 1 and 2 Protection
The short-circuit current in discharge (SCD) function detects catastrophic current conditions in the discharge
direction. The short-circuit in discharge thresholds and delay times are configurable via the SCD1_CONTROL
and SCD2_CONTROL registers. The thresholds and timing can be fine-tuned even further based on a sense
resistor with lower resistance or wider tolerance via the PROTECTION_CONTROL register. The detection circuit
also incorporates a blanking delay before disabling the CHG and DSG FETs. When an SCD event occurs, the
LATCH_STATUS[SCD1] or LATCH_STATUS[SCD2] bit is set to 1 and is latched until it is cleared and the fault
condition has been removed.
7.3.20 Primary Protection Features
The bq27750 gas gauge supports the following battery and system level protection features, which can be
configured using firmware:
• Cell Undervoltage Protection
• Cell Overvoltage Protection
• Overcurrent in CHARGE Mode Protection
• Overcurrent in DISCHARGE Mode Protection
• Overload in DISCHARGE Mode Protection
• Short Circuit in CHARGE Mode Protection
• Overtemperature in CHARGE Mode Protection
• Overtemperature in DISCHARGE Mode Protection
• Precharge Timeout Protection
• Fast Charge Timeout Protection
7.3.21 Gas Gauging
This device uses the Impedance Track™ technology to measure and determine the available charge in battery
cells. The accuracy achieved using this method is better than 1% error over the lifetime of the battery. There is
no full charge/discharge learning cycle required. See the Theory and Implementation of Impedance Track Battery
Fuel-Gauging Algorithm Application Report (SLUA364) for further details.
7.3.22 Charge Control Features
This device supports charge control features, such as:
• Reports charging voltage and charging current based on the active temperature range—JEITA temperature
ranges T1, T2, T3, T4, T5, and T6
• Provides more complex charging profiles, including sub-ranges within a standard temperature range
• Reports the appropriate charging current required for constant current charging and the appropriate charging
voltage needed for constant voltage charging to a smart charger, using the bus communication interface
• Selects the chemical state-of-charge of each battery cell using the Impedance Track method
• Provides pre-charging/zero-volt charging
• Employs charge inhibit and charge suspend if battery pack temperature is out of programmed range
• Reports charging faults and indicates charge status via charge and discharge alarms
7.3.23 Authentication
This device supports security by:
• Authentication by the host using the SHA-1 method
• The gas gauge requires SHA-1 authentication before the device can be unsealed or allow full access.
Copyright © 2017, Texas Instruments Incorporated
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