I have an existing circuit using the AD5421 as a 2-wire loop-powered transmitter. It has a CPU, LCD display, sensor ADC, and an AD5700 for Hart transmission. Works great.
My customer wants to add additional circuitry that would only be used if the device was connected in a 3-wire configuration, since it would draw too much current for loop power. So the device would be able to operate as either a loop-powered (2-wire) device or as an externally powered 3-wire device with additional capabilities.
Can I accomplish this with the AD5421?
If so, what do I need to change?
If not, is there another part that I can use?
You will have to look for another part which is AD5420.
So the 3 wires are:
The goal is to also be able to operate as a 2-wire device without the extra features. It looks to me like the AD5420 does not operate in this mode.
I'm trying to create a dual mode device that operates as a simple 2-wire loop-powered unit AND/OR as a 3-wire device with additional features.
Any suggestions on how to implement a combination 2-wire / 3-wire device? AD parts I can use? Any way to do it with the AD5421 so I can re-use my existing design?