Charging System Safety Circuit

Product Status: Mass Production


The ISL9211B is an integrated circuit (IC) optimized to provide a redundant safety protection to a Li-ion battery charging system. The IC monitors input voltage, battery voltage, and charge current. When any of these parameters exceeds its limit, the IC turns off an internal N-channel MOSFET to remove power from the charging system to the battery. The IC also monitors its own internal temperature and turns off the N-channel MOSFET when the temperature exceeds +150°C. Together with the battery charger IC and the protection module in a battery pack, the charging system using the ISL9211B has triple-level protection and is two-fault tolerant.

The IC is designed to turn on the internal NFET slowly, to avoid in-rush current at
power-up. It turns off the NFET quickly when the input is overvoltage, to remove power before damage occurs. The ISL9211B has a logic flag output to indicate a fault condition. The enable input allows the system to cut off the input power, if needed.


  • 24V Max Input Voltage
  • Supports Up To 2.0A Input Current
  • Fully Integrated Protection Circuit for Three Protected Variables
  • High Accuracy Protection Thresholds
  • User Programmable Overcurrent Protection Threshold
  • Responds to Input Overvoltage in Less Than 1µs
  • High Immunity of False Triggering Under Transients
  • Fault Indication for Various Fault Occurrence
  • Easy to Use
  • Pb-Free (RoHS Compliant)


 Block Diagram


Basic Information
Production Status
Mass Production
Programmable Overcurrent Range (A)
0 to 2.0
Input Overvoltage Protection Typ
5.8 V
Battery Overvoltage Protection Typ
4.34 V
Battery Leakage
20nA max @ 4.34VVB
Battery Overvoltage Protection Min
4.25 V
Battery Overvoltage Protection Max
4.4 V
Input Overvoltage Protection Min
5.6 V
Input Overvoltage Protection Max
6 V
Programmable Overcurrent (max)
2 A
Ron At 500mA (typ)
170 mΩ
Ron At 500mA (max)
280 mΩ
Qualification Level
Battery Overvoltage Protection
4.34 typ, 4.25 min, 4.4 max
Input Overvoltage Protection
5.8 typ, 5.6 min, 6.0 max
Ron at 500 mA
170 typ, 280 max
Temperature Range
-40 to +85

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