The 1B22 is an isolated voltage-to-current converter that incorporates transformer isolation to achieve high performance and automated surface mount manufacturing for low cost and increased reliability. Designed for industrial applications， it is especially suited for harsh environments with extremely high common-mode interference. With programmable inputs and outputs， the 1B22 provides an unbeatable combination of versatility and performance in a compact plastic package. Functionally， the V/I converter consists of four basic sections： input conditioning， modulator/demodulator， isolated loop supply and current source （Figure 1）。 The 1B22 is pin programmable for 0 V to +5 V or 0 V to +10 V inputs and 0 to 20 mA or 4 to 20 mA outputs using an internal resistor network. It can also be set by an external resistor to accept 0 V to +1 V to 0 V to +10 V inputs. Transformer coupling provides 1500 V rms galvanic isolation between the inputs and the current loop. Nonlinearity is an excellent ±0.05% max. Loop power is generated internally through a dc/dc converter and is also isolated from the input side （1500 V rms）。 Loop compliance voltage is dependent on the voltage supplied to the 1B22， and with VLOOP = 28 V， it is sufficient to drive a 1000 ? load. The 1B22 is fully specified over –25°C to +85°C and operates over the industrial （–40°C to +85°C） temperature range.