ZHCSKH8C December 2009 – December 2019 BQ24072T , BQ24075T , BQ24079T
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 说明 （续）
- 6 Device Options
- 7 Pin Configuration and Functions
- 8 Specifications
-
9 Detailed Description
- 9.1 Overview
- 9.2 Functional Block Diagram
- 9.3
Feature Description
- 9.3.1 Undervoltage Lockout (UVLO)
- 9.3.2 Overvoltage Protection (OVP)
- 9.3.3 Dynamic Power-Path Management
- 9.3.4 Battery Charging
- 9.3.5 Charge Current Translator
- 9.3.6 Battery Detection and Recharge
- 9.3.7 Termination Disable (TD Input, BQ24072T)
- 9.3.8 Battery Disconnect (SYSOFF Input)
- 9.3.9 Dynamic Charge Timers (TMR Input)
- 9.3.10 Status Indicators (PGOOD, CHG)
- 9.3.11 Thermal Regulation and Thermal Shutdown
- 9.3.12 Battery Pack Temperature Monitoring
- 9.4 Device Functional Modes
-
10Applications and Implementation
- 10.1 Application Information
- 10.2
Typical Applications
- 10.2.1
Using the BQ24075T, BQ24079T to Disconnect the Battery from the System
- 10.2.1.1 Design Requirements
- 10.2.1.2
Detailed Design Procedure
- 10.2.1.2.1 Program the Fast Charge Current (ISET):
- 10.2.1.2.2 Program the Input Current Limit (ILIM):
- 10.2.1.2.3 Program 6.25-hour Fast-Charge Safety Timer (TMR):
- 10.2.1.2.4 TS Function:
- 10.2.1.2.5 CHG and PGOOD LED Status:
- 10.2.1.2.6 Processor Monitoring Status:
- 10.2.1.2.7 System ON/OFF (SYSOFF):
- 10.2.1.2.8 Selecting IN, OUT and BAT Capacitors
- 10.2.1.3 Application Curves
- 10.2.2 BQ24072T in a Host Controlled Charger Application
- 10.2.1
Using the BQ24075T, BQ24079T to Disconnect the Battery from the System
- 11Power Supply Recommendations
- 12Layout
- 13器件和文档支持
- 14机械、封装和可订购信息
9.3.11 Thermal Regulation and Thermal Shutdown
The BQ2407xT contain a thermal regulation loop that monitors the die temperature. If the temperature exceeds TJ(REG), the device automatically reduces the charging current to prevent the die temperature from increasing further. In some cases, the die temperature continues to rise despite the operation of the thermal loop, particularly under high VIN and heavy OUT system load conditions. Under these conditions, if the die temperature increases to TJ(OFF), the input FET Q1 is turned OFF. FET Q2 is turned ON to ensure that the battery still powers the load on OUT. Once the device die temperature cools by TJ(OFF-HYS), the input FET Q1 is turned on and the device returns to thermal regulation. Continuous overtemperature conditions result in a "hiccup" mode. During thermal regulation, the safety timers are slowed down proportionately to the reduction in current limit.
Note that this feature monitors the die temperature of the BQ2407xT. This is not synonymous with ambient temperature. Self heating exists due to the power dissipated in the IC because of the linear nature of the battery charging algorithm and the LDO associated with OUT. A modified charge cycle with the thermal loop active is shown in Figure 17. Battery termination is disabled during thermal regulation.
Figure 17. Charge Cycle Modified by Thermal Loop