STMicroelectronics Makes Lithium Batteries Perform Better and Last Longer with High-Accuracy BMS Controller

­STMicroelectronics’ L9961 battery-management-system (BMS) device provides market-leading accuracy and flexibility to enhance the performance, lifetime, and safety of Li-ion and Li-polymer batteries.

Suitable for battery packs up to 25V, the L9961 provides monitoring, balancing, and protection of batteries for diverse applications requiring the high energy density of lithium batteries. Cordless power tools, backup energy-storage systems, uninterruptible power supplies, portable and semi-portable equipment, and medical devices can benefit from the L9961’s advanced features.

The many built-in features include a dual pre-driver for controlling battery-pack safety relays, which can be programmed for high-side and low-side connection.  An embedded non-volatile memory for configuration data relieves the microcontroller from reprogramming the device at each startup. An I2C interface handles configuration and host communication to share battery state-of-charge (SOC) and state-of-health (SOH).

Thanks to a high-resolution analog-to-digital converter (ADC) and current-sense amplifier, the L9961 senses cell voltages with an accuracy of ±15mV and battery current to within 0.25%. The accurate measurements enable high-accuracy passive cell balancing and coulomb counting, and support safety features including overvoltage and undervoltage detection, balance undervoltage protection, overcurrent detection, and short-circuit in-discharge protection. When an external thermistor is connected, the L9961 performs pack temperature monitoring with over/under-temperature detection and pack-fuse management. The L9961 is also highly robust to support hot plugging.

While extending the battery lifetime and increasing safety, the L9961 consumes minimal energy from the battery pack. Two power-saving modes cut the current consumption down to 2μA in deep-sleep and 5μA in standby with the integrated voltage regulator active to resume operation quickly.

The L9961 is in production and is available now in a 32-lead 5mm x 5mm x 1mm VFQFPN package, prices start from $1.19 for orders of 1000 pieces.

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