A high voltage analog multiplexer with digital calibration for battery management systems

This work presents a multi-channel high voltage analog multiplexer with digital calibration for battery management systems (BMS). For a high voltage battery management systems, the front end circuit must be able to accommodate input voltage up to tens of volts, perhaps even hundreds of volts. To realize a possible solution on silicon, the front end of BMS shall be fabricated using an advanced HV (high voltage) semiconductor process, which usually is constrained by the voltage limitation between gate and source of HV devices. To overcome such a limitation, a high voltage gate control circuit is proposed in this work, including digital calibration that can compensate the output voltage loss of the multiplexer. An experimental prototype is implemented using a typical 0.25 μm 1-poly 3-metal 60V BCD process. The post-layout-extracted simulation results reveal that the worst-case error is less than 2 mV with calibration, which is 91% improvement compared with the state of art based on thorough simulations.

I. Introduction

High voltage (HV) BMS is widely needed in many applications, e.g., EV and HEV, where many battery modules are assembled and integrated. These modules are composed of many series of batteries to generate a high supply voltage. If the battery module is made of series batteries, they will be unavoidably unbalanced among battery cells in voltage and capacity after a few times of charging and discharging cycles. Notably, the above hazard is always happened no matter when the battery module is charging and discharging. If either over-charge or over-discharge occurs to any battery cell, the efficiency and health of the battery will be degraded. What even worse is that the Li-lon battery might be burned out and exploded. Therefore, BMS with charge equalization is critically required in battery-operated applications.