Li-ion battery management ICs target higher-power applications

December 05, 2013 // By Graham Prophet
Rohm Semiconductor has a new member of its IC series providing high-accurate charge/discharge control, monitoring and protection functions for Li-ion secondary battery packs, in this case intended for a wide range of applications such as e-bikes, power tools and (hybrid) electrical vehicles

The ML5218 is a Li-ion battery monitoring IC for packs of five to 16 cells, detecting over-charge or over-discharge and over-current of each cell. This makes the device adaptable to systems using safer lithium iron phosphate batteries of multiple cells connected in series. Operating current consumption is similar to that of conventional models. Current consumption in the power-down mode is minimised to close to zero, and the load on the battery pack during long-term storage has been reduced significantly. The built-in 100mA cell-balancing switch eliminates the need for an external circuit for cell balancing, facilitating a low-cost system design. A battery remaining-charge display function is configured using up to five external LEDs. Monitoring of temperatures for up to eight locations is implemented by connecting thermistors. The ICs also integrate the Gate driver for an automatic ON/OFF control of the external N-channel FET for charge and discharge.

For a complete protection solution, ROHM has the external MCU ML610Q486P which can be used in combination with the ML5238. The MCU is an 8-bit high-performance controller based on the low power ML610Q4xx MCU series with integrated Flash memory to store the register settings. The monitoring IC can provide the 3.3V power supply to the MCU so that no external voltage regulator is needed. Based on voltage measurments of each cell or the entire battery pack, as well as monitoring of charge and discharge current, it can perform actions to protect the batteries and to prevent the system reaching an irregular state. Features include;

Power Supply voltage: +7V to +80V

Highly accurate voltage measurement ( ±10 mV)

Highly accurate charge/discharge current measurement ( ±0.5A)

Overcharge detection voltage: + 3.3V to +4.4V

Cell balancing function

Charge/discharge control with N-channel FET

Temperature measurement function of battery pack (-30°C to +85°C), (max) eight thermistors

Short-circuit detection and protection

Low Power Consumption

Operating temperature: -40°C to +85°C

Gas-gauge LED drivers; five level indication (max.)

Monitoring the