I'm attempting to interface a HART signal with the DAC161S997EVM and also need to modify how it connects. I noticed that the schematic in SNLU146.pdf is not complete and it appears the capacitors are not connected correctly. Namely C1 and C3 on the schematic are reversed compared to the DAC161S997 data sheet pinout.
I also have been simulating my desired circuit using the model in the dac161s997 data sheet, Figure 14. HART Signal Injection. If I simulate that circuit it appears to be correct. However if I test on the demo board, this does not seem to be totally accurate. My assumption, based on Figure 14, is that there is a virtual ground on the amplifier that mirrors the current to the output. The source current DAC is filtered with 3 15K resistors. It seems to me that the DC voltages on these nodes C1, C2, and C3 have a DC bias to them and don't match simulation or this model. Is there a more accurate model?
Is there anyway to get corrected schematic for the demo board, determine if the demo board is incorrectly wired, and if there is a better model for the HART filter stage. I have LTSpice circuit model I can make available. The simulation matches exactly what the data sheet shows in Figure 14. I just can't get the DEMO board to also match correctly.
In addition to the possible board errors, the capacitance added to the loop output attenuates HART signals and needed to be removed.