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DAC8742HEVM: Schematic vs Datasheet

Part Number: DAC8742HEVM
Other Parts Discussed in Thread: DAC8742H, PROFIBUS

Hello Team,

My customer noticed that in the datasheet for the DAC8742H it specifies a shunt 0.022uF cap to GND and a series 4700pF cap on the MOD_OUT line (page 29). However, in the user guide for the DAC8742H EVM it uses a series 2.2uF capacitor followed by a 0.022uF shunt cap to GND. Can you please explain why one topology was used in the datasheet and another on the EVM.



  • Renan,

    I'm not sure why the schematics are different. It's possible that one or the other was used to accommodate changes from HART and Fieldbus/PROFIBUS, or if we had made some changes in the schematic to tighten up the EVM for HART certification.

    In the end it shouldn't make much difference. The series 2.2uF capacitor is a big DC blocking capacitor that comes in at a very low frequency. The issue may be that the HART requires some sort of bandpass filtering. If you make the frequency too low, there may be more noise in the signal.

    I believe that the circuit in the DAC874xHEVM passed HART certification. There's more information in the following app note and TI Design, which you can review for the circuit.

    Joseph Wu