SMT172 to I²C Interface Board

Function: I²C Interface and Conversion from SMT172 to SMT160-30 Temperature sensor output

Introduction

Regularly Smartec is asked for a temperature sensor with an I2C output. Because of the low power consumption of the SMT172 sensor itself, the self heating of the sensor is negligible, which contributes to its precision. An on chip integrated I2C interface would produce too much heat. The only way to preserve the sensors precision and still have an I2C interface, is to combine them on a tiny pcb. This board also does the calculations on the sampled duty-cycle and converts the result in ASCII data with an accuracy in the range of mK.

The board can be used in PWM mode (instead of I2C mode), to meet compatibility requirements with some existing (obsolete) SMT160-30 applications.

The output signal

The output signal is a standard compatible I2C signal (slave) and the standard address is 111 (0x6F). A secondary address (7 bits) with the default value of 115 (0x73) is available. The value of this secondary address can be changed by the user. This process will be explained below.

Highlights

  • Accurate measurement in full SMT172 temperature range
  • Measures the output of the SMT172 in 0.001 °C steps
  • Both I2C and PWM (SMT16030 like) output
  • Board temperature range 0 – 75 °C
  • Programmable secondary address, allowing for multiple sensors with interfaces on the same I2C bus
  • 3.3 V. regulator for powering the SMT172
  • Powered by the I2C bus itself
  • Can be used for all housings of the SMT172

PDF: SMT172TOIIC.

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