SLYT847 May   2024 DAC161S997 , DAC8551 , TVS3301

 

  1.   1
  2. 1 Introduction
  3. 2 4mA to 20mA transmitter basics
  4. 3 4mA to 20mA transmitter design aspects
  5. 4 Design performance metrics
  6. 5 Transmitter circuit implementations
  7. 6 Dedicated loop converter
  8. 7 Loop transmitter device
  9. 8 MCU integrated DAC
  10. 9 PWM-based DAC
  11. 10Stand-alone low power DAC
  12. 11Implementations Comparison
  13. 12Conclusion
  14. 13Related websites

7 Loop transmitter device

Another implementation uses a low-power DAC such as the DAC8551, followed by a dedicated loop transmitter such as the XTR115 with an integrated LDO, voltage reference and output amplifier. This approach minimizes noise and has less than 1% gain error.

There are a couple of limitations: the XTR115 operating temperature is limited to 85°C, and the integrated LDO has a maximum input of 36V. As an alternative, the XTR117 comes in a smaller package, consumes lower quiescent current, and operates at temperatures as high as 125°C. The XTR117’s integrated LDO works up to 40V. The XTR117 does not integrate a voltage reference, so counting an external reference, the solution becomes a three-device solution: an LDO, a DAC and a voltage reference, as shown in Figure 5.

Two-wire 4mA to 20mA transmitter using the XTR117. Figure 5 Two-wire 4mA to 20mA transmitter using the XTR117.