システムボード 6792

MAXREFDES1161: Small Form Factor, High Accuracy, 2-Wire, 4mA to 20mA Current Loop Transmitter


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Input Type VIN (MIN)
(V)
VIN (MAX)
(V)
IOUT
(A)
Single/Multiple
Output
VOUT
(V)
POUT
(W)
Isolated/Non-Isolated Topology
DC 4 36 0.02 Single     Non-Isolated  

The MAXREFDES1161 is a small form factor, high accuracy, 2-wire 4mA to 20mA transmitter which integrates all functional and protection blocks in a small 1.0in x 0.6in dual-row header footprint that is compatible with breadboards and off-the-shelf peripheral expansion boards. The function block is implemented with the MAX12900, which is an ultra-low power, highly integrated analog front end (AFE) for a 4mA to 20mA sensor transmitter that includes 10 building blocks in a small package. The wide input supply voltage LDO generates the low noise power rail for the device and can also be used to power an external low power microcontroller found in a typical smart sensor application. Two general purpose amplifiers and one low drift amplifier are used to achieve the current loop control in combination with a discrete transistor and a current monitor. Two pulse-width modulated (PWM) conditioner circuits receive two 8-bit PWM signals from a microcontroller and output stable PWM amplitude over the voltage supply and temperature variation. Two comparators can be used for diagnostic functions or as general-purpose comparators. A low drift voltage reference can provide offset loop current and a power-up sequencer allows for a smooth power up. The MAXREFDES1161 uses the MAX12900 to achieve a total solution for industrial loop-powered current transmitters which convert the microcontroller 16-bit PWM signal to current without using a DAC, greatly reducing total system cost without degrading the accuracy. The 4mA to 20mA current loop transmitter can achieve a 1μA resolution and provide diagnostic functionality, such as loop power monitoring and current readback. The reference design integrates protection functions, such as loop power reverse protection and overvoltage protection, and can support up to 40V loop power input at 4mA current output. The MAXREFDES1161 can be used to evaluate the performance of the MAX12900 and can be directly used in final products to simplify the current loop transmitter design and shorten development cycles.

Key Features

  • Robust operation with wide range of input voltage
  • Small form factor
  • Complete solution without external components needed
  • Reverse voltage protection
  • Overcurrent protection
  • Additional available comparator
  • Dual PWM input
  • Power supply for external low-power microcontroller
  • Power-up sequencing
MAXREFDES1161 Board 拡大表示+


This board is not available for purchase.

Designed, Built, Tested

This document describes the hardware design shown in Figure 1. It provides a detailed systematic technical guide to designing a loop-powered 4mA to 20mA transmitter using Maxim’s MAX12900.

Design Resources

 
Status:
Package:
Temperature:

MAX12900
超低電力4~20mAセンサートランスミッタ

  • 広い入力電源範囲:4.0V~36V
  • 超低消費電力:170µA (typ)
  • 高リニアリティ:0.01% (最大誤差)