BMS Voltage Measurement Special Edition | OCT621X: Making Cell Monitoring More Accurate and Safer
In the high-voltage system of new-energy vehicles, the Battery Management System (BMS) can be described as the "brain" of the battery pack; precise measurement of cell, module, and busbar voltages is therefore critical to enabling the BMS to achieve reliable sensing and safe control. High-voltage-side voltage sampling not only requires multi-channel monitoring through high-frequency switching but must also balance electrical isolation safety with sampling data accuracy. The OCT621X automotive high-voltage optocoupler, a dedicated isolated solid-state switching device designed for high-voltage platforms, provides an ideal solution for BMS voltage measurement MUX applications and is the preferred choice for automotive high-voltage measurement.
Real-world industry pain points in BMS voltage measurement scenarios
BMS voltage measurement is a typical low-current, high-frequency switching application characterized by a large number of cell sampling channels; furthermore, the entire system operates within a high-voltage battery pack environment, imposing extremely stringent requirements on core components. On the one hand, reliable isolation must be achieved between the high-voltage side and the low-voltage control side (AFE/ADC) to prevent high-voltage leakage from damaging the downstream control chips; on the other hand, the sampling paths must exhibit extremely low leakage current and low on-resistance to minimize measurement drift caused by the components themselves, while also requiring the components to support controlled failure to ensure system safety during fault conditions. In addition, the wide temperature operating range, surges, and ESD shocks inherent to the in-vehicle environment impose even higher standards on component stability and reliability.
OCT621X precisely addresses the core challenges in BMS measurement
The OCT621X is specifically designed for automotive high-voltage measurement applications. Leveraging superior core performance parameters, it addresses key industry challenges in BMS voltage measurement. The product features a high isolation withstand voltage of 5000 Vrms/1 min, a leakage current upon turn-off ≤ 1 μA, a typical on-resistance as low as 0.16 Ω for the 60 V version and as low as 0.3 Ω for the 100 V version, switching speeds in the microsecond range, and stable operation across a full temperature range of-40 °C to 85 °C. It also complies with automotive surge and ESD protection requirements, supports a controllable failure design, and fully meets BMS system requirements in terms of safety, measurement accuracy, switching efficiency, and reliability.
Typical Applications and Design Considerations for OCT621X in BMS
In BMS voltage measurement circuits, the OCT621X functions as a solid-state MUX switch in the form of an opto-relay. It is connected in series between the Cell/Module/Pack sampling path and the AFE/ADC; together with voltage divider resistors, RC circuits, and a clamp protection circuit, it forms a complete sampling chain. This enables multi-channel switching, allowing voltage signals from different cells, modules, and packs to be multiplexed onto the same set of AFE/ADC channels for synchronous measurement. While simplifying the circuit design, the device achieves safe electrical isolation between the high-voltage and low-voltage sides through its high isolation characteristics. Its core design boundaries are clearly defined: it is intended solely for switching between measurement and diagnostic paths and does not participate in the power on/off operation of the high-voltage main circuit; it strictly complies with the functional safety design specifications for automotive high-voltage systems. Furthermore, the OCT621X has passed multiple UL/VDE/CQC certifications and meets RoHS environmental requirements. By employing automotive-grade design and production standards throughout the entire process, it provides a robust quality guarantee for the long-term stable operation of BMS systems.
With its combination of high isolation, low leakage current, low on-resistance, and wide-temperature stability, the OCT621X enables safe isolation of small signals on the high-voltage side and high-frequency solid-state switching in BMS voltage measurement applications, making cell and module voltage measurements more accurate and safer; it is therefore the preferred component for high-voltage measurement in automotive BMS systems.
