TIDUF16 December   2023

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Photodiode, TIA, and ADC
      2. 2.2.2 LED Driving
      3. 2.2.3 Power
      4. 2.2.4 Display, Orientation, and Communication Features
      5. 2.2.5 Software
        1. 2.2.5.1 Timing Structure
        2. 2.2.5.2 Oversampling and Digital Filtering to Increase Dynamic Range
        3. 2.2.5.3 Calculating Vitals
    3. 2.3 Highlighted Products
      1. 2.3.1 MSPM0L1306
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software Requirements
      1. 3.2.1 TI GUI
      2. 3.2.2 CCS Project
      3. 3.2.3 Analog Engineers Calculator
    3. 3.3 Test Setup
    4. 3.4 Test Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks

2.2.2 LED Driving

The AFE Block Diagram (Figure 2-2), shows that the power of each LED is managed by the MOSFET and controlled via the GPIO pins of the MSPM0L1306. These two MOSFETS control the on and off states of the LEDs respectively. TIDA-010267 uses single-part LEDs with wavelengths of 660 nm (red) and 940 nm (IR). LED brightness control is achievable thanks to the internal 8-bit DAC of the MSPM0L1306 and OPA voltage follower outputting to a common MOSFET that determines the current flow through the LEDs. Because the voltage of the battery can be monitored periodically with an internal ADC connection and internal voltage reference, it is possible to reliably attenuate the voltage output of the DAC to a known level and pinpoint the desired current flow through the LEDs.