If characteristic impedance along a transmission line mismatch on a printed circuit board, high-speed signal has serious signal integrity problems. When signal path of a differential pair jumps layers, mismatched impedance between differential via and differential line will affect the signal integrity. The models of a coupled transmission line and via are presented in this paper. Impedance matching of the coupled transmission line and differential via for differential signals is studied. The effects of differential via dimensions on differential signals is simulated and analyzed.

Based on the characteristics of power Li-ion battery, a distributed battery management system (BMS) is designed and implemented for electric vehicle (EV), which is composed of a master system and several measurement modules. The measurement modules are embedded into various numbers of cells and detect the status information of the battery. The system structure is highly flexible and reliable. The testing results of this BMS with a battery charge and discharge test equipment show that it can measure and display the status information of the battery precisely and reliably with a flexible structure, which supports EVs running safely and reliably.

Battery management system (BMS) takes a key role in battery health management and life extension of electric vehicles. It contains various analogue-digital hybrid circuits above the frequency range of several hundred mega-Hertz, where the signal integrity and system stability are probably affected by certain issues of circuit design. In this report, the signal reflections along the transmission lines in a BMS are theoretically simulated and analyzed. The performance of the system is compared to that after optimization both in theory and measurement. The simulation and experimental results verify that electrical impedance matching is most crucial to the signal integrity and system stability in the system design.