STMicroelectronics' L9962 battery-management IC pairs a 12-bit ADC for cell-voltage measurement with a 70mA cell-balancing current, aimed squarely at 10-cell lithium-ion and lithium-polymer packs. At $2.89 each in 1,000-unit quantities, it lands in the price band where cordless power tools, e-bikes, medical devices, and UPS backup units live.

The device covers the full monitoring chain: voltage, current, temperature, balancing, and protection. It measures individual cell voltages on a continuous cycle with programmable loop time and trips balancing and protection functions when it detects overvoltage or undervoltage. A plausibility check compares the total stack voltage against the detected cell count, catching wiring faults before they corrupt the readings.

How accurate is the current measurement?

Current sensing runs through an integrated high-accuracy sense amplifier using Coulomb counting (integrating current over time to track charge in and out of the pack). ST specifies 0.25% current-measurement accuracy over the full operating-temperature range — a figure that matters because Coulomb-counting drift compounds over the pack's life. The same amplifier path enables detection of excessive charge and discharge currents plus short-circuit discharge protection.

Cell-voltage accuracy is also maintained across the full temperature range, which ST says keeps cell voltages tightly aligned. Note the distinction: voltage accuracy through the internal ADC is a design claim from the datasheet, while the 0.25% current figure is the headline specification.

Thermal monitoring uses an NTC thermistor (a resistor whose resistance drops as temperature rises) with ratiometric measurement, flagging both over-temperature and under-temperature conditions. The ratiometric approach cancels reference-drift errors by measuring the thermistor relative to a known divider.

What else does the integration remove from the BOM?

The L9962 consolidates several functions that normally need external circuitry:

• Battery-pack fuse management
• Configurable high-side and low-side pre-drivers for pack relays
• A 3.3V LDO that stays live in standby to power an external MCU or indicator LEDs

An I2C interface lets the host configure parameters such as the voltage-measurement interval and read back state-of-charge (SOC) and state-of-health (SOH) data. For battery-gauge accuracy, that means the coulomb-counter output feeds the host's SOC algorithm rather than forcing designers to add a separate fuel-gauge chip.

How much power does it burn when idle?

Quiescent current is where portable designs win or lose runtime. The L9962 draws 5µA in standby and 2µA in deep-sleep — a mode ST positions specifically for products sitting in transit or on a shelf. For a pack that may spend months between charge cycles, that 2µA figure is the difference between a battery that arrives ready to work and one that arrives flat.

Packaging and positioning

The chip ships in a 7mm × 7mm 48-pin TQFP. The target applications are 3- to 10-cell series stacks: cordless power tools, portable and semi-portable medical equipment, light electric vehicles such as e-bikes and scooters, and UPS-style backup storage.

For practitioners, the open question is whether the integrated stack — 12-bit ADC, coulomb counter, relay drivers, and LDO in one package — displaces the multi-chip BMS arrangements common at this cell count, and how the 0.25% current spec holds up against your calibration interval in the field.

By Sophie Lindqvist