The TC500/500A/510/514 family are precision analog front ends that implement dual slope A/D converters having a maximum resolution of 17 bits plus sign. As a minimum, each device contains the integrator, zero crossing comparator and processor interface logic. The TC500 is the base (16 bit max) device and requires both positive and negative power supplies. The TC500A is identical to the TC500, except it has improved linearity allowing it to operate to a maximum resolution of 17 bits. The TC510 adds an onboard negative power supply converter for single supply operation. The TC514 adds both a negative power supply converter and a 4 input differential analog multiplexer. Each device has the same processor control interface consisting of 3 wires: control inputs A and B and zerocrossing comparator output (CMPTR). The processor manipulates A, B to sequence the TC5xx through four phases of conversion: Auto Zero, Integrate, Deintegrate and Integrator Zero. During the Auto Zero phase, offset voltages in the TC5xx are corrected by a closed-loop feedback mechanism. The input voltage is applied to the integrator during the Integrate phase. This causes an integrator output dv/dt directly proportional to the magnitude of the input voltage. The higher the input voltage, the greater the magnitude of the voltage stored on the integrator during this phase. At the start of the Deintegrate phase, an external voltage reference is applied to the integrator, and at the same time, the external host processor starts its on-board timer. The processor main-