A high EMS current-mode SPI interface for battery monitor IC (BMIC) is presented to form a daisychain bus configuration for the cascaded BMICs and the communication between the MCU and master BMIC.Based on analog and digital mixed filtering technique,the proposed daisy-chain can avoid the isolated communication issue in electromagnetic interference environment,and reduce the extensively required I/O ports of MCU,at the same time reduce the system cost.The proposed daisy-chain interface was introduced in a 6-ch battery monitor IC which was fabricated with 0.35 μm 30 V BCD process.The measurement result shows that the presented daisy-chain SPI interface achieves better EMS performance with different EMI injection while just consuming a total operation current up to 1 mA.