BQ77908A is a battery protection and battery balancing device for lithium-ion and lithium polymer battery packs. The BQ77908A monitors Series 4 to 8 individual cell voltages and provides a fast-acting output that can be used to drive an N-channel mosfet interrupt power path.
BQ77908A Pin Configuration
Activation delay and recovery methods under safe conditions are fully programmable in non-volatile memory. An internal 50ma battery circuit is used to provide automatic battery balancing. The robust balancing algorithm ensures optimal performance by keeping all battery voltages balanced. Balancing can be configured to operate at all times, only during charging, or can be disabled entirely
Other advanced safety features of the BQ77908A include the ability to control a split power path mosfet, a slotted sensing mechanism, and the ability to detect fault conditions in slotted or short-circuited external temperature sensors.
Overview
The BQ77908A battery protection and battery balancer for Li-ion and Li-polymer battery packs monitors series 4 to 8 individual cell voltages and provides a fast-acting output that can be used to drive N-channel MosFeTs to interrupt the power path. Activation delay and recovery methods under safe conditions are fully programmable in non-volatile memory. An internal 50ma battery circuit is used to provide automatic battery balancing. The robust balancing algorithm ensures optimal performance by keeping all battery voltages balanced. Balancing can be configured to operate at all times, only during charging, or can be disabled entirely.
BQ77908A Functional Block Diagram
The BQ77908A provides the following protection functions:
● Battery overvoltage
● Battery undervoltage
● Discharge overcurrent
● The discharge current is short-circuited
● Charging current is short-circuited
Features
● 4-, 5-, 6-, 7-, or 8 series cell protection
● Individual battery voltage monitoring
● Low side NMOS FEts drive charging and Quantity control
● Compatible with 1-mΩ current sensing resistors
● Supply voltage ranges from 5.6V to 40V
● Integrated 3.3v micro-power LDO regulator
● Low supply current
- Normal mode :50 μA, typical
- Shutdown mode, LDO OFF: 5µA, typical
● 38-pin TSSOP package
● Internal 50mah automatic battery balancing
Applications
● Cordless power tools
● Cordless lawn equipment
● Electric bicycle
● UPS
● Light Electric Vehicle (LEV)
