I am implementing 4~20mA Transmitter that consist of a MCU, a current DAC, and an ADC for measuring an analog signal.
I would like to electrically isolate the analog signal from the loop current so that the higher end control system (i.e master system) is not damaged by some outrageous condition on the lower end (i.e sensor) side.
I've searched various solutions on-line and found that I could either use isolated ADC or digital isolator for I2C or SPI.
However, my device is loop powered, so everything must be done within about 3mA to be safe.
The isolation devices I found on major IC makers normally consume more than 1.6mA per channel.
Anybody have better idea or parts that I could use?
Best Answer
The ADuM1441 can be used to implement an isolated SPI interface, and dissipates less than 1 mA at 2 Mbps. Quiescent power dissipation can be lower than 1 uA, making this product ideal for isolated 4-20 mA loop applications.