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Couple of questions re: AD5629R power-down behavior

Question asked by KE5FX on Mar 12, 2015
Latest reply on Mar 22, 2015 by KE5FX

Hi -- I've got two questions on the data sheet for the AD5629R (Rev. D).


1) Page 21 says that "Individual channel power-down is not supported while using the internal reference."  Does this mean that none of the 0100 commands (Power down/power up DAC) are supported in that case?  If not, what exactly are the power-control features that aren't available when using the internal reference?


2) Is it possible to mix and match various power down modes across individual channels?  In other words, can I issue a series of commands like the following:


   0100xxxx xxxxxx01 00010100 (Power down channels C and E with 1K to GND)

   0100xxxx xxxxxx11 00100001 (Power down channels A and F with three-state outputs)

   0100xxxx xxxxxx01 00100000 (Change power-down mode on channel F only to 1K)


... without changing the output impedance of any previously-powered-down channels?


Similarly, I assume that the only way to power a channel back up is to set its bitmask to '1' with mode bits 00, correct?   Am I correct in that this sequence will not power channel A back on?


   0100xxxx xxxxxx01 00000001 (Power down channel A with 1K to GND)

   0100xxxx xxxxxx01 00000000 (Clearing the bit for channel A does/does not power it back up...?)


I'm 99% sure I understand the underlying logic but wanted to make sure, especially with regard to whether any of the commands still work with the internal reference enabled.  I don't understand why there would be a connection between the choice of reference sources and the output control bits.