When it comes to providing accurate reference voltages and similar low-current-demand voltage sources, a parallel reference - also known as a shunt reference - is the most effective. With the REF1112, TI adds a shunt reference to its nano voltage family.

The success of linear regulators such as the LM317 or the LM7805 pushed shunt references into the background. This, however, is not justified - while linear regulators need a bit of current to supply their inner circuitry, a shunt reference’s simpler application schematic means that it can make do with less.

In the REF1112, Texas Instruments manages to use only one microampere. The part, furthermore, comes in an extremely small SOT-23 housing.

Simplicity Breeds Quality

For the reference voltage provided by the REF1112, Texas Instruments sets the part to 1.25 V. This voltage level is commonly known as the reference voltage used in various other linear and switching regulators and can be used as a reference potential for various circuits.

Furthermore, the REF1112 data sheet specifies the explicit levels shown in the figure. Texas Instruments particularly emphasizes the high accuracy and the low-temperature coefficient, which means that the voltage reference will remain stable even as the ambient temperature changes.

Interestingly, Texas Instruments furthermore provides histograms which show component distribution over values - it is obvious that the REF1112 is, to some level, also intended as a metrology-grade reference.

One interesting aspect of the REF1112 is that it behaves just like a Zener diode. This means that the reverse voltage behavior mirrors that of a normal diode, with voltage drops similar to those of small signal diodes such as the 1N4148.

Furthermore, the correct value for the series resistor must be selected. It is mainly responsible for dissipating excess voltage. The datasheet provides a variety of nomograms and formulas that greatly simplify selecting the correct value.

Interestingly, voltage regulator accuracy can be increased by adding two capacitors. A 1 uF capacitor should be used to bypass the main power supply, while the regulator's load must provide a minimum of 0.01 uF in capacitance. In practice, any MLCC capacitor can be used—it does not cost much and can be placed directly next to the SOT-23 housing containing the actual voltage reference integrated circuit.

Welcome to The Family

The maximum dissipation is limited to five milliamperes. While this should be ample for most voltage reference tasks, some circuits need more supply current. In this case, Texas Instruments recommends the deployment of an operational amplifier. The data sheet recommends the use of the OPA347.

However, this is but one of many low-power components found in the Texas Instruments portfolio. Those looking for operational amplifiers can also look at the OPA349 and TLV240x families, while the datasheet suggests the TLV349x family if a voltage comparator is needed. Of course, Texas Instruments provides a wide array of additional low-power semiconductors, which can be used to complete the analog front end.

Conclusion

If a voltage reference with minimal power consumption is required, the Texas Instruments REF1112 is the circuit of choice. It boasts an extremely low quiescent current, is highly stable, and always deserving of a recommendation.