Other Parts Discussed in Thread: DAC161S997,
Hello All
I have designed schematic of isolated pressure transmitter with HART feature. Kindly please check and suggest whether it is OK or not.
Nakul Audeechya
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Hello All
I have designed schematic of isolated pressure transmitter with HART feature. Kindly please check and suggest whether it is OK or not.
Nakul Audeechya
Nakul,
I only have a few comments for you on this schematic. I've concentrated on mostly the DAC8740H and the DAC161S997 in this schematic.
For the cap on MOD_IN, 100nF for C10 seems high to me, and I would just recommend the same value as we use in the example schematic in the datasheet of 2200pF. Also on the MOD_OUT pin, you have C8 set to 220nF which is very high. The datasheet specifies a range for the MOD_OUT of 5nF to 22nF. However, it's best not to use the maximum because parasitic capacitance would increase the value even more. The MOD_OUT pin may have problems driving above 22nF of capacitance.
For the pull-up on ERRB for the DAC161S997, I think a 1MΩ resistor for R8 would be rather slow. I'd probably use a 10kΩ resistor.
What models of ferrites are you using for L3 and L4 for the power in the DAC161S997?
Joseph Wu
Hi Joseph
Thank you for carefully look in my circuit.
I have used Ferrite Bead, 1000 ohm @ 100 MHz, 0.25 A 0402 for L3,L4 and Ferrite Bead, 600 ohm @ 100 MHz, 1.5 A, 1206 for L1, L2.
What do you think about C9 and C17? Because C8 is already in the same path.
Nakul
Nakul,
The ferrites should be fine in your circuit.
For the C8, C9, and C17, I generally will go by the capacitors outlined in the EVMs. For C9 and C17, I would leave them as 6800pF and 0.22uF as in the DAC161S977EVM. For C8, earlier, I had recommended reducing it and I would still do that, but I don't think the capacitor is strictly necessary. I would still reduce it and leave it as uninstalled.
Joseph Wu