BQ27750 Datasheet, PDF (22/34 Pages) Texas Instruments – Impedance Track Battery Gas Gauge and Protection Solution for 1-Series Cell Li-Ion Battery Packs

bq27750
SLUSCM7 – JUNE 2017
Typical Applications (continued)
8.2.1 Design Requirements (Default)
Design Parameter
Cell Configuration
Design Capacity
Device Chemistry
Cell Overvoltage at Standard Temperature
Cell Undervoltage
Shutdown Voltage
Overcurrent in CHARGE Mode
Overcurrent in DISCHARGE Mode
Short Circuit in CHARGE Mode
Short Circuit in DISCHARGE 1 Mode
Safety Overvoltage
Under Temperature Charging
Under Temperature Discharging
BROADCAST Mode
www.ti.com
Example
1s1p (1-series with 1 parallel)
4400 mAH
100 (LiCoO2/graphitized carbon)
4300 mV
2500 mV
2300 mV
6000 mA
–6000 mA
0.1 V/Rsense across SRP, SRN
–0.1 V/Rsense across SRP, SRN
4500 mV
0°C
0°C
Enabled
8.2.2 Detailed Design Procedure
8.2.2.1 Setting Design Parameters
For the firmware settings needed for the design requirements, refer to the bq27750 Technical Reference Manual
(SLUUBI6).
• To set the 1s1p battery pack, go to data flash Configuration: DA Configuration register's bit 0 (CC0) = 1.
• To set design capacity, set the data flash value to 4400 in the Gas Gauging: Design: Design Capacity
register.
• To set device chemistry, go to the data flash I²C Configuration: Data: Device Chemistry. The bqStudio
software automatically populates the correct chemistry identification. This selection is derived from using the
bqCHEM feature in the tools and choosing the option that matches the device chemistry from the list.
• To protect against cell overvoltage, set the data flash value to 4300 in Protections: COV: Standard Temp.
• To protect against cell undervoltage, set the data flash value to 2500 in the Protections: CUV register.
• To set the shutdown voltage to prevent further pack depletion due to low pack voltage, program Power:
Shutdown: Shutdown voltage = 2300.
• To protect against large charging currents when the AC adapter is attached, set the data flash value to 6000
in the Protections: OCC: Threshold register.
• To protect against large discharging currents when heavy loads are attached, set the data flash value to
–6000 in the Protections: OCD: Threshold register.
• Program a short circuit delay timer and threshold setting to enable the operating the system for large short
transient current pulses. These two parameters are under Protections: ASCC: Threshold = 100 for charging
current. The discharge current setting is Protections: ASCD:Threshold = –100 mV.
• To prevent the cells from overcharging and adding a second level of safety, there is a register setting that will
shut down the device if any of the cells voltage measurement is greater than the Safety Overvoltage setting
for greater than the delay time. Set this data flash value to 4500 in Permanent Fail: SOV: Threshold.
• To enable the internal temperature and the external temperature sensors: Set Settings:Configuration:
Temperature Enable: Bit 0 (TSInt) = 1 for the internal sensor; set Bit 1 (TS1) = 1 for the external sensor.
• To prevent charging of the battery pack if the temperature falls below 0°C, set Protections: UTC:Threshold
= 0.
• To prevent discharging of the battery pack if the temperature falls below 0°C, set Protections:
UTD:Threshold = 0.
• To provide required information to the smart chargers, the gas gauge must operate in BROADCAST mode.
To enable this, set the [BCAST] bit in Configuration: I²C Configuration 2: Bit 0 [BCAST] = 1.
22
Submit Documentation Feedback
Product Folder Links: bq27750
Copyright © 2017, Texas Instruments Incorporated