A Look At Voltage Reference ICs. Part 2
Analog Devices » ADR3412/ ADR3420/ ADR3425/ ADR3430 /ADR3433/ ADR3440/ ADR3450
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.
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.
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.
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.
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.
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:
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.
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.
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