Im using an AD5541 and I am finding some problems figuring out how the R-2R is configured. Is there a way of obtaining the Req for a set configuration? Is this resistance linear??
Thanks in advance
Figure 22 in the data sheet shows the R-2R architecture. The DAC is designed in such a way that the resistance the VREF pin sees is always the same. This prevents current glitches on the reference when the user changes DAC codes. From the Vout pin the resistance will change depending on the DAC code. However, the AD5541 requires an op-amp on the Vout pin as shown in figure 23 to ensure that the DAC output is linear. Taking current from the Vout pin will prevent that.
If you are interested in programmable resistance have a look at Analogs digiPOT portfolio.
If this hasn't answered your question please post a follow up.
Yes, I am interested in a programmable resistance but I dont know if your digiPOT portfolio can fulfill my requirements since Im looking for precise ohm variation and linearity. Thats the reason I look for a device like AD5541.
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