A 250-Mbps 2.6-ns Propagation Delay Capacitive Digital Isolator with Adaptive Frequency Control

A capacitive digital isolator with adaptive frequency control is proposed to reduce the power consumption while maintaining high data rates and low propagation delays. An on-off keying (OOK) modulation is employed in a differential output transmitter (TX) with a local oscillator (OSC). By adjusting the frequency of the OSC according to the pulse width of the input random bit sequence, the currents dissipation of OSC is greatly reduced from 919 $\mu$A to 4S.4$\mu$A at 1 Mbps data rate and 459.2 $\mu$A at 250 Mbps data rate, respectively. The receiver (RX) mainly consists of a preamplifier and an envelope detector for low propagation delays. Simulation results show that the proposed architecture achieves a 250 Mbps data rate and a 2.6 ns propagation delay. With a load of 15 pF, TX and RX consume 413 $\mu$A and 1 mA currents at 1 Mbps data rate and 1.5 mA and 4.6 mA currents at 250 Mbps data rate, respectively.