Multi-cell battery pack monitor for smallest Li-ion pack designs

March 14, 2017 // By Graham Prophet
Intersil, now a subsidiary of Renesas, has added the ISL94202 3-to-8 cell battery pack monitor that supports lithium-ion (Li-ion) and other battery chemistries used in applications such as vacuum cleaners, lawn equipment, handheld power tools, e-bikes, scooters, toys, and energy storage systems.

The monitor enables ultra-small 2-terminal designs, and accurately monitors, protects and cell-balances rechargeable battery packs to ensure safe operation and charging. The ISL94202 operates as a stand-alone battery protection system using an internal state machine with five pre-programmed modes for accurately balancing and controlling each battery cell. It monitors and protects the battery pack from catastrophic events such as hardware faults, short circuit conditions, and cell voltage overcharge/over-discharge and meets the UL2054, UL2271/72 and IEC62133 specified pack safety requirements. Designers can program the ISL94202 battery monitor’s protection settings to enable small and low-cost battery packs without requiring an external microcontroller. If required, the ISL94202 can also communicate with an external microcontroller via I ²C serial bus to provide additional fuel gauge measurements, including state of charge and state of health information. Precise fuel gauge status is provided by the device’s high-side current measurement feature.

 

The ISL94202 integrates high-side charge/discharge FET drive circuitry to interface to tools or electric motor equipment. The device also controls external passive cell balancing switches to ensure good cell energy matching while protecting the pack’s cell life from chronic undercharging. The IC can withstand factory pack assembly hot plug events, which greatly simplifies manufacturing.

 

Features include;

• Eight cell voltage monitors support Li-ion CoO 2, Li-ion Mn 2O4, and Li-ion FePO 4 battery chemistries

• Highest level of integration: cell voltage level shift, automatic cell balance, 14-bit ADC, current sense monitor, power FET control, and temperature sensor interface

• Stand-alone pack control, no microcontroller required

• Multiple cell voltage protection options up to 4.8V

• Programmable detection/recovery times for overvoltage, undervoltage, overcurrent and short circuit conditions

• Configuration/calibration registers stored in EEPROM

• Open battery connect detection

• Integrated charge/discharge FET drive circuitry with built-in charge pump supports high-side N-channel FETs

• Cell balancing uses external FETs with device’s internal state machine or external microcontroller

• Operates over the