An Area-Efficient High-Precision Analog Front End for Battery Management System

An analog front end (AFE) for monitoring the voltages of a stack of sixteen Li-ion batteries is presented. Each cell has a conversion voltage range of 0 to 5 V, allowing for a stack maximum input voltage of up to 80 V. The gate voltage bootstrap switch in high-voltage applications accurately measures battery voltage, reducing nonlinear sampling errors and significantly shrinking circuit size by omitting LDMOS devices. Furthermore, the high voltage switch charge injection cancellation is adopted to counteract the error introduced by the asymmetric sampling switches. All sixteen channels were sampled and amplified within $16~{\mu }$ s. The AFE is fabricated using a $0.18~{\mu }$ m high-voltage BCD process, and the total circuit area is 0.32 mm2. The measurement error for the 16-channel battery voltage is within 1 mV.