SLAA835B May   2018  – August 2018 MSP430FR2353 , MSP430FR2355

 

  1.   Smart Analog Combo Enables Tomorrow's MCU-Based Sensing and Measurement Applications
    1.     Trademarks
    2. 1 Introduction
    3. 2 Smart Analog Combo Applications
      1. 2.1 Smoke Detection
      2. 2.2 Gas or PM2.5 Detector
      3. 2.3 Blood Glucose Meter or Oximeter
      4. 2.4 Current-Loop Transmitter
      5. 2.5 Small Form-factor Pluggable (SFP) optical transceivers
      6. 2.6 Audio Applications
    4. 3 Conclusion
    5. 4 References
  2.   Revision History

2.1 Smoke Detection

There are two methods for smoke detection using ACmeasurement or DC measurement.

For AC measurement, a general voltage signal conditioner measures the photodiode current, through a DC blocker (usually a large capacitor) before analog-to-digital conversion. Figure 1 shows an AC measurement-based smoke detector implemented using two smart analog combo SAC-L3 configurations.

block-diagram-ac-measurement-smoke-detector.pngFigure 1. Block Diagram Showing AC Measurement in a Smoke Detector Application Using the MSP430 Smart Analog Combo

For DC measurement, a current-to-voltage converter (usually a transimpedance amplifier (TIA) with low-leakage input) measures the photodiode current, with an optional second-stage voltage signal conditioner before analog-to-digital conversion. By replacing the feedback circuit with a diode or transistor, the application can include a logarithmic amplifier in parallel to extend the measurable dynamic range by compressing the large signal outputs The smart analog combo can act as a TIA, and internal connections with the ADC and a paired SAC can save more GPIOs. Figure 2 shows a DC measurement-based smoke detector implemented using the smart analog combo SAC-L3 configuration.

block-diagram-dc-measurement-smoke-detector.pngFigure 2. Block Diagram Showing DC Measurement in a Smoke Detector Application Using the MSP430 Smart Analog Combo