A single-chip 4-20mA temperature transmitter at embedded world 2015

Feb 25, 2015

Last week I wrote about the number of Industrial Communication Solutions supported by MSP430 microcontrollers (MCUs), the most popular among them being the 4-20 mA current loop. We will be showcasing this solution at the embedded world tradeshow in Germany this week. So what exactly is the 4-20 mA solution?

The current solutions can be either 2-wire current loops that provides the communication channel and power to the field transmitter or the 3-wire current loops that have a separate power line not associated directly with the 4-20mA current loop. In this kind of communication, the resolution is by voltage controlled current source and the total current budget for 2-wire field transmitter is less than 3-3.5mA. This makes the ultra-low-power MCUs extremely suitable for 2-wire communication loop solutions.

Many solutions use external ADCs, Op Amps, and DACs to achieve the current loop solution as shown below :

However integration of signal conditioning and current control have significant benefits as compared to discrete solutions. TI's single-chip 4-20mA temperature transmitter solution features an ultra-low-power MSP430F2274 MCU is such a solution that:

• provides full turnkey solution for RTD temperature transmitter over current loop

• provides single chip cost effective system solution

• provides for simplified board designs

TI Design: TIDA-00247

This complete solution features :

• Single-chip 4-20mA and RTD solution

• RTD signal conditioning with integrated OpAmp

• 4-20mA modulation of external transistor circuit established by PWM using 16-Bit Timer

• Less than 1mA system current operation

• 12-Bit resolution of output 4-20mA signal

• Full software solution

This is good for the following industrial applications:

• Factory automation and process control

• Sensors and field transmitters

• Building automation

If you're lucky enough to be at embedded world 2015, check out more details at the TI Booth!