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A Look At Voltage Reference ICs. Part 2

Analog Devices » ADR3412/ ADR3420/ ADR3425/ ADR3430 /ADR3433/ ADR3440/ ADR3450

Sam Davis

Power Electronics

Part 1

Linear Technology

Linear Technology’s LT6656 (Fig. 2) is a precision series voltage reference that draws less than 1 μA of supply current and can operate with a supply voltage within 10 mV of the output voltage. The LT6656 offers an initial accuracy of 0.05% and temperature drift of 10 ppm/°C. The LT6656 can supply up to 5 mA of output drive with 65 ppm/mA of load regulation, allowing it to be used as the supply voltage and the reference input to a low power ADC. The LT6656 can accept a supply voltage up to 18 V and withstand the reversal of the input connections. The LT6656’s output is stable with 1 μF or larger output capacitance and operates with a wide range of output capacitor ESR.

A Look At Voltage Reference ICs
Figure 2. The combined low power and precision characteristics of the LT6656
are ideal for portable and battery powered instrumentation.

This reference is fully specified for operation from –40 °C to 85 °C, and is functional over the extreme temperature range of –55 °C to +125 °C. The LT6656 is offered in the 6-lead SOT-23 and (2 mm ×2 mm) DFN Packages.

National Semiconductor

Available in three accuracy grades, the LM4030 is a precision shunt voltage reference with an initial accuracy at 0.05% (Fig. 3). The LM4030 exhibits 75 ppm thermal hysteresis and 40 ppm long-term stability as well as immunity to board stress effects.

A Look At Voltage Reference ICs
Figure 3. The LM4030 is intended for space critical applications
because of its tiny SOT-23 package.

The LM4030’s design eliminates the need for an external stabilizing capacitor while ensuring stability with any capacitive load, thus making the LM4030 easy to use. It is available with fixed voltage options of 2.5 V and 4.096 V.

Table 1. National Semiconductor LM4030
Parameter Value
Output voltage tolerance
(A grade, 25 °C)
±0.05% (max)
Output noise (10 Hz to 10 kHz) 105 µVpp
Minimum operating current 120 µA
Extended temperature range –40 °C to +125 °C
Temperature coefficient 10 ppm/°C (max)
A Grade

The LM4030 utilizes fuse and zener-zap reverse breakdown voltage trim during wafer sort to ensure an accuracy of better than ±0.05% (A grade) at 25 °C and guaranteed temperature coefficient of better than 10 ppm/°C. Table 1 lists the LM4030’s specifications.


The MAX6330/MAX6331 combine a precision shunt regulator with a power-on reset function in a single SOT23-3 package. The shunt regulator consists of a pass device and a controlling circuit, as illustrated in Fig. 4. The pass device allows the regulator to sink current while regulating the desired output voltage within a ±1.5% tolerance. The shunt current range (ISHUNT) is 100 μA to 50 mA.

A Look At Voltage Reference ICs
Figure 4. The MAX6330 is a shunt regulator that consists of a pass device
that allows the reference to sink current while regulating the
desired output voltage within a ±1.5% tolerance.

Both active-low (MAX6330) and active-high (MAX6331) push/pull output versions are available. The output voltage has ±1.5% tolerance. The MAX6330/MAX6331 operate over a wide shunt current range from 100 μA to 50 mA, and offer very good transient immunity.

A 3-pin SOT23 package reduces board space and improves reliability compared to multiple-IC/discrete solutions.

The pass transistor in the MAX6330/MAX6331 maintains a constant output voltage (VSHUNT) by sinking the necessary amount of shunt current. When ILOAD is at a maximum, the shunt current is at a minimum, and vice versa:

When choosing the external resistor, consider:

  1. The input voltage range, (VIN)
  2. The regulated voltage, (VSHUNT)
  3. The output current range, (ILOAD)


The TS3431 (Fig. 5) is a programmable shunt voltage reference with guaranteed temperature stability over the entire operating temperature range (–40 °C to +125 °C). The output voltage can be set to any value between 1.24 V and 24 V with an external resistor bridge.

A Look At Voltage Reference ICs
Figure 5. Compatible with industry-standard TL431, the TS3431
is a programmable shunt voltage reference.

Available in SOT23-3 surface mount package, it can be used in application designs where space saving is critical. Table 2 lists the TS3431 specifications.

Table 2. STMicroelectronics TS3431 specifications
Parameter Value
Adjustable output voltage 1.24 to 24 V
Precision levels @25 °C ±2%, ±1%, ±0.5%
and ±0.25%
Sink current capability 0.4 to 100 mA
Industrial temperature range –40 °C to +125 °C

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