Where can I get information on interfacing the AD5700 HART Modem and the AD5410/20 current output DAC?
There is both an Application Note and Circuit Note available on this topic, describing two alternative methods of interfacing the AD5420 with the AD5700 HART Modem. Web links have been included below:
Could you explain the pros and cons of either approach?
AD5421 seems can only take HART input from Cin, right?
The AD5422 is a 16 bit Vo & Io DAC (AD5412 is the 12 bit option) and the AD5420 is a 16 bit Io only DAC (AD5410 is the 12 bit option). Both products have the option of coupling the HART signal into either the CAP2 pin or the Rset pin. The CAP2 option is covered in AN-1065, while the Rset option is covered in CN-0270 & CN-0278.
The advantage of the Rset coupling option over the CAP2 option is that it is more immune to noise on the power-supply line coupling onto the loop but a disadvantage might be the fact that the design must use the external Rset option and also a high precision external Rset needs to be included in the BOM. On the otherhand, if the CAP2 option is used, either the Rset internal or external option can be used in the design.
The AD5421 is a 16-bit loop-powered Io DAC. In this case, the HART signal is generally coupled into the Cin pin of the AD5421, but should a design require that the slew rate control and the HART coupling functions be kept independent, the HART signal could be coupled into the Rext2 pin. Again, this option would force the design into using the external Rset resistor.
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