Which reference should I choose to get the best performance from the AD5541A/42A?
Suitable external references include the ADR421 and ADR431.Both are low noise reference sources and have the required noise/accuracy level to achieve the best performance from the AD5541A/42A.
The reference buffer is also critical to the design because the input impedance at the DAC reference input is heavily code- dependent and will lead to linearity errors if the DAC reference is not adequately buffered.The low power AD8657 is a suitable the voltage reference buffer.
In the circuit below it is setup as a force and sense configuration (Kelvin sensing) as the low impedance output reference buffer for the AD5542A. The AD8657 has an open-loop gain of 120 dB and is a precision, 18 V, 50 nV/√Hz op amp. With a maximum offset voltage of 350 μV, typical drift of less than 2 μV/°C, and noise of 5 μV p-p (0.1 Hz to 10 Hz), the AD8657 is well suited for applications where error sources need to be minimized. The other half of the AD8657 is used as the output amplifier.
The combination of parts shown in below gives us the required performance but also minimizes PC board area, as well as power dissipation. The AD5542A is available in a 3 mm × 3 mm, 16-lead LFCSP or 16-lead TSSOP package. The AD5541A is available in 3 mm × 3 mm, 10-lead LFCSP or 10-lead MSOP. This combination of parts provides industry-leading 16-bit integral nonlinearity (INL) of ±1 LSB and differential nonlinearity (DNL) of ±1 LSB with guaranteed monotonicity, as well as low power, small PCB area, and cost effectiveness.
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