Charging System Safety Circuit

Product Status: Mass Production


The ISL9209B is an integrated circuit (IC) optimized to provide a redundant safety protection to a Li-ion battery from failures of a charging system. The IC monitors the input voltage, the battery voltage and the charge current. When any of the three parameters exceeds its limit, the IC turns off an internal P-Channel MOSFET to remove the power from the charging system. In addition to the above protected parameters, the IC also monitors its own internal temperature and turns off the P-Channel MOSFET when the temperature exceeds +140°C. Together with the battery charger IC and the protection module in a battery pack, the charging system using the ISL9209B has triple-level protection and is two-fault tolerant.

The IC is designed to turn on the internal PFET slowly to avoid inrush current at power up but will turn off the PFET quickly when the input is overvoltage in order to remove the power before any damage occurs. The ISL9209B has a logic warning output to indicate the fault and an enable input to allow the system to remove the input power.


  • Fully Integrated Protection Circuit for Three Protected Variables
  • High Accuracy Protection Thresholds
  • User Programmable Overcurrent Protection Threshold
  • Input Overvoltage Protection in Less than 1µs
  • High Immunity of False Triggering Under Transients
  • Warning Output to Indicate the Occurrence of Faults
  • Enable Input
  • Easy to Use
  • Thermal Enhanced TDFN Package
  • Pb-Free Plus Anneal Available (RoHS Compliant)


 Block Diagram


Basic Information
Production Status
Mass Production
Programmable Overcurrent Range (A)
0 to 1.5
Input Overvoltage Protection Typ
5.58 V
Battery Overvoltage Protection Typ
4.34 V
Battery Leakage
20nA max @ 4.34VVB
Battery Overvoltage Protection Min
4.28 V
Battery Overvoltage Protection Max
4.4 V
Input Overvoltage Protection Min
5.65 V
Input Overvoltage Protection Max
6 V
Programmable Overcurrent (max)
1.5 A
Ron At 500mA (typ)
250 mΩ
Ron At 500mA (max)
450 mΩ
Qualification Level
Battery Overvoltage Protection
4.34 typ, 4.28 min, 4.4 max
Input Overvoltage Protection
5.58 typ, 5.65 min, 6.0 max
Ron at 500 mA
250 typ, 450 max
Can Sample
Temperature Range
-40 to +85

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