BQ40Z50-R2 Datasheet, PDF (29/51 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
Typical Applications (continued)
9.2.1 Design Requirements
Table 1 shows the default settings for the main parameters. Use the bqStudio tool to update the settings to meet
the specific application or battery pack configuration requirements.
The device should be calibrated before any gauging test. Follow the procedures on the bqStudio Calibration
page to calibrate the device, and use the information on the bqStudio Chemistry page to update the match
chemistry profile to the device.
Table 1. Design Parameters
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 Mode
Safety Overvoltage
Cell Balancing
Internal and External Temperature Sensor
Undertemperature Charging
Undertemperature Discharging
BROADCAST Mode
Battery Trip Point (BTP) with active high interrupt
EXAMPLE
3s1p (3-series with 1 Parallel)⁽¹⁾
4400 mAh
1210 (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
Disabled
External Temperature Sensor is used.
0°C
0°C
Disabled
Disabled
(1) When using the device the first time and if a 1-s or 2-s battery pack is used, then a charger or power supply should be connected to the
PACK+ terminal to prevent device shutdown. Then update the cell configuration (see the bq40z50-R2 Technical Reference Manual
[SLUUBK0] for details) before removing the charger connection.
9.2.2 Detailed Design Procedure
9.2.2.1 High-Current Path
The high-current path begins at the PACK+ terminal of the battery pack. As charge current travels through the
pack, it finds its way through protection FETs, a chemical fuse, the Li-Ion cells and cell connections, and the
sense resistor, and then returns to the PACK– terminal (see Figure 22). In addition, some components are
placed across the PACK+ and PACK– terminals to reduce effects from electrostatic discharge.
9.2.2.1.1 Protection FETs
Select the N-channel charge and discharge FETs for a given application. Most portable battery applications are a
good match for the CSD17308Q3. The TI CSD17308Q3 is a 47A, 30-V device with Rds(on) of 8.2 mΩ when the
gate drive voltage is 8 V.
If a precharge FET is used, R1 is calculated to limit the precharge current to the desired rate. Be sure to account
for the power dissipation of the series resistor. The precharge current is limited to (V_CHARGER – V_BAT)/R1 and
maximum power dissipation is (V_charger – V_bat)²/R1.
The gates of all protection FETs are pulled to the source with a high-value resistor between the gate and source
to ensure they are turned off if the gate drive is open.
Copyright © 2017, Texas Instruments Incorporated
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