Although the 4-20 mA analog loop is so old it could easily be phased out, it remains the undisputed standard in process and regulation technology. This is because the relatively simple two-wire technology is highly reliable and easy to implement. However, supplying digital components with unused portions of the loop current has become a challenge since microprocessors process raw data and HART (Highway Addressable Remote Transducer) modems ensure that smart sensors send a variety of different data over the same loop.
Conventional switching regulator ICs cannot be used for this task because, while highly efficient at full load, they quickly exceed the 4 mA limit even at minimal loads. The low quiescent current in standby mode doesn't help, as the main output voltage is completely off. Even using linear regulators is not ideal. Its quiescent current of approximately 0.5 mA is significantly within acceptable limits, but the poor efficiency means that the available power is less than that of switching regulators (by a factor of approximately 3).
This is where the R420-1.8/PL switching regulator, recently developed by Recom, offers a particularly clever solution. Thanks to its novel topology, the no-load current has been reduced by around 100 μA while still delivering the full nominal voltage at the output. For example, with 24 VDC,
another advantage of the new switching regulator is that it can be programmed with a simple circuit and a resistor for all output voltages between 1.8 V and 5 V. Therefore, a single component can be used for various tasks in process automation and in sensor-controlled, solar-powered systems. The new R420-1.8 SMD features an open-frame design, operates in a temperature range of -40 to +105°C, and can be used at altitudes up to 5,000 m. It is permanently protected against short circuits and comes with a 3-year warranty.

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