1B21AN

Overview

The Analog Devices 1B21AN is an isolated, loop-powered voltage-to-current converter designed for industrial applications. It provides galvanic isolation of 1500 V rms via transformer coupling, eliminating ground loops and protecting against transients. The device accepts input voltages from 0 V to 10 V and converts them into programmable current outputs of either 4 mA to 20 mA or 0 mA to 20 mA. It operates over a rated temperature range of −25°C to +85°C and features low nonlinearity (±0.02% typical) and high common-mode rejection (90 dB minimum). The unit requires external ±15 V power supplies for the input side and a loop supply up to 30 V for the output side.

Feature Summary

• Transformer-based signal and power isolation ensures complete galvanic separation between input and output circuits.
• Flexible input conditioning allows mapping of various voltage ranges to standard industrial current loops with minimal external components.
• Compact DIP package facilitates high channel density in multichannel systems while maintaining robust transient protection capabilities.

Applications

• Multichannel process control systems
• DAC to current loop interface circuits
• Analog transmitters and controllers
• Remote data acquisition systems

Procurement Notes

Verify the specific suffix AN indicates the −25°C to +85°C rated performance variant when sourcing. Confirm that the required external power supplies match the specified ±15 V for the input side and the appropriate loop voltage for the output side. Ensure that the application environment does not exceed the maximum operating temperature of +85°C. Check datasheet specifications for total output error and offset drift if precision trimming is required for the specific installation conditions.

Selection Notes

Select the 1B21AN when high common-mode voltage isolation is critical to prevent ground loop interference in noisy industrial environments. Choose this component for applications requiring a compact solution for converting analog voltage signals into standardized 4-20 mA or 0-20 mA current loops. Consider the external resistor network requirements for gain and offset adjustments based on the specific input voltage span and desired output current range.

Part Context

The 1B21 series serves as a specialized interface between low-voltage analog sources and industrial current loop standards. The 1B21AN specifically denotes the version optimized for the −25°C to +85°C temperature range, distinguishing it from broader operating variants. This part integrates modulation, demodulation, and isolation technologies into a single package to simplify system design for remote sensing and control tasks.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.

FAQ

How is the 4 mA to 20 mA output range achieved?

A 4 mA offset is created by feeding a current derived from the internal +6.225 V reference into the summing node using an external offset resistor (RO).

What is the maximum load resistance supported?

The device can drive a maximum load resistance of 1.35 kΩ when powered by a 30 V loop supply, providing a compliance voltage of at least 27 V.

Does the device require external buffers or drivers?

No, the 1B21 performs complete isolated voltage-to-current conversion with minimum external parts, and no external buffers or drivers are required.