Recom – New switching regulator supplies digital components from 4-20mA loop


RECOM has launched the R420-1.8/PL switching regulator, which is intended to be used to supply microprocessors and microcontrollers from a 4-20mA loop.

The benefits of the flat module include its very low stand-by power consumption, and its high conversion efficiency in normal operation.

The analogue 4-20mA loop is commonly used in process and control technology, because of its simple two-wire topology, which is reliable and easy to install. The unused portion of the loop current may be used to supply digital components. This calls for regulation to step the input from the 4-20mA loop down to the level required by a digital component.

Conventional switching regulators, which offer high efficiency at full load, are unsuitable as their poor conversion efficiency at low loads means that they are incapable of meeting the output-power requirements from a 4mA input.

Linear regulators are also unsuitable: their poor efficiency decreases the power available from the 4-20mA supply by a factor of around three compared to switching regulators.

To solve this problem, RECOM developed the R420-1.8/PL switching regulator, which draws a stand-by current of just 100μA while maintaining the rated output voltage. For example, from a 24V DC input sourcing less than 3.5mA, the R420 can provide a 10mA output at 3.3V. This is enough to supply a sensor alongside an MCU and HART modem without affecting the loop’s functionality or the accuracy of the measurement instrument connected to it.


  • Open-frame, surface-mount unit
  • Adjustable output-voltage range: 1.8V-5V
  • Short-circuit protection
  • Operating-temperature range:
    -40°C to 105°C
  • Three-year warranty


  • Industrial equipment
  • Process-control systems
  • Factory-automation equipment