Intrinsically safe cable drive circuit

摘要

A cable drive circuit allows a transmitter in a process control system to drive signals across a capacitive length of cable. The cable drive circuit uses a charge pump to store charge, which is then used in conjunction with open drain outputs to transmit logic signals across a cable to a peripheral at the other end of the cable. A microcontroller or other device specifies the number of communication pulses to send across the cable before allowing the charge pump to recharge. By transmitting communication pulses for a small percentage of the time the average current is minimized, making the circuit suitable for operation under the 4-2OmA standard for two-wire devices.