VOUT = 0V to 5V
VOUT = 0V to 4.092V
SNAS348G – MAY 2006 – REVISED APRIL 2016
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10 Power Supply Recommendations
10.1 Using References as Power Supplies
While the simplicity of the DAC124S085 implies ease of use, it is important to recognize that the path from the
reference input (VREFIN) to the VOUTs has essentially zero Power Supply Rejection Ratio (PSRR). Therefore, it is
necessary to provide a noise-free supply voltage to VREFIN. To use the full dynamic range of the DAC124S085,
the supply pin (VA) and VREFIN can be connected together and share the same supply voltage. Because the
DAC124S085 consumes very little power, a reference source may be used as the reference input or the supply
voltage. The advantages of using a reference source over a voltage regulator are accuracy and stability. Some
low noise regulators can also be used. Listed below are a few reference and power supply options for the
The LM4132, with its 0.05% accuracy over temperature, is a good choice as a reference source for the
DAC124S085. The 4.096-V version is useful if a 0-V to 4.095-V output range is desirable or acceptable.
Bypassing the LM4132 VIN pin with a 0.1-µF capacitor and the VOUT pin with a 2.2-µF capacitor improves
stability and reduce output noise. The LM4132 comes in a space-saving 5-pin SOT23.
Figure 37. LM4132 Power Supply
Available with accuracy of 0.44%, the LM4050 shunt reference is also a good choice as a reference for the
DAC124S085. It is available in 4.096-V and 5-V versions and comes in a space-saving 3-pin SOT23.
Figure 38. LM4050 Power Supply
The minimum resistor value in the circuit of Figure 38 must be chosen such that the maximum current through
the LM4050 does not exceed its 15-mA rating. The conditions for maximum current include the input voltage at
its maximum, the LM4050 voltage at its minimum, and the DAC124S085 drawing zero current. The maximum
resistor value must allow the LM4050 to draw more than its minimum current for regulation plus the maximum
DAC124S085 current in full operation. The conditions for minimum current include the input voltage at its
minimum, the LM4050 voltage at its maximum, the resistor value at its maximum due to tolerance, and the
DAC124S085 draws its maximum current. These conditions can be summarized with Equation 4 and Equation 5.