Abstract: Based on bulk silicon 0.25 μm BCD process, a codec scheme for magnetic isolation drive circuit is designed. The digital signal to be transmitted is encoded into two high-frequency pulses with different widths. The primary winding of the transformer is coupled to the secondary winding and is detected by the secondary side circuit and finally restored to the input signal at the output. Compared with the codec scheme for traditional magnetic isolation drive circuit, the magnetic isolation drive circuit designed in this paper has a novel encoding and decoding method, and the circuit is simple to be realized. The delay time of the transmitted signal is greatly reduced and the frequency is higher. The simulation results show that the circuit can work normally under the voltage of 3~5 V, which can achieve the maximum data isolation transfer rate of 125Mbps.The maximum delay time is only 8ns, and the quiescent current is 1.64mA with the dynamic power of 0.37mA/Mbps.