Li-ion Secondary Protection LSI Supports 14 Cells

ROHM Group company LAPIS Semiconductor has recently announced the availability of a lithium-ion battery secondary protection LSI that supports up to 14 cells in series, claimed to be the most in the industry, and features a maximum operating voltage of 80V, delivering functional safety in li-ion battery-equipped systems such as electric bicycles, power storage systems, and UPS.

In recent years, the number of applications using high energy density li-ion batteries has risen dramatically. However, there is a growing need to comply with functional safety standards that protect lives and property while providing a higher degree of reliability. And although li-ion batteries also require measures against over-charge/discharge, the number of cases using secondary LSIs in the event of failure is increasing to meet societal demands for further reliability following expanding applicability.

Until now, LAPIS Semiconductor has been focused on developing battery monitoring LSIs, but has recently begun expanding its lineup to meet the need for secondary protection LSIs that play a key role in preventing accidents when battery monitoring LSIs mounted in li-ion systems stop operating due to failure.

The ML5232 enables detection of up to 14 cells in series, significantly reducing the number of external components and minimizing board space while simplifying circuit design compared with conventional secondary protection LSIs that support only 4 cells. In addition, two protection signals are output that simultaneously cut the fuse and turn off the charge control MOSFET when overvoltage is detected, increasing system reliability.

Key features include: Industry-best 14-cell serial connection reduces system size by approximately 50% Unlike conventional secondary protection LSIs that support only 4 or 5 cells in series, the ML5232 ensures compatibility with up to 14 li-ion batteries in series by adopting mixed-signal circuitry and high-voltage processes. This reduces the number of external parts and decreases mounting area by approximately 50%, contributing to system miniaturization. In addition, construction of high-voltage systems is enabled, making it possible to achieve a standard (common) platform for a wide range of applications.

Two unique protection signals used during overvoltage detection The ML5232 immediately outputs protection signals when secondary protection LSIs utilized in li-ion battery monitoring systems stop working due to failure. 2 output pins (Nch open drain + CMOS) are included that block charging paths, allowing the charge control MOSFET to be turned OFF while simultaneously cutting the fuse during overvoltage detection, improving system reliability.