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Interleaving the output of two AD5781 DACs

Question asked by davFis on May 9, 2016
Latest reply on May 31, 2016 by davFis


I would like to use the AD5781 18 bit DAC for audio playback and waveform synthesis. It has wonderful static DC characteristics, but has a large glitch and settling time issues that limit it's dynamic performance. One way around this problem would be to interleave the output of two DACs, that is output the stable and set voltage of one while changing the value of the other and swapping between them.


As the AD5781 has a settling time of about 1usec, I was aiming at interleaving the output of the two DACs at about 800kHz, this would allow 16x oversampling of 44.1kHz content and makes the design of the analogue reconstruction filter a bit easier.


Unfortunately, I am not an electronic engineer, but I want a way of switching between the outputs of these two DACs while retaining their 4ppm DC voltage accuracy.  I have looked at hundreds of analog switches and other types of switches too.


The switching between the two DACs could be performed directly (by placing an analog switch in the signal path) between the DAC and the next stage or indirectly (by placing the analog switch between ground and the signal path) or even possibly (placing the switch between the inputs of the differential input of an op-amp, forcing it to common mode).


I know this is a very broad question, but I would like some suggestions on the best way of switching between the output these two DACs.