SBAS650C May   2014  – April 2021 AFE4403

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Family Options
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Timing Requirements: Supply Ramp and Power-Down
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Receiver Channel
        1. 8.3.1.1 Receiver Front-End
        2. 8.3.1.2 Ambient Cancellation Scheme and Second Stage Gain Block
        3. 8.3.1.3 Receiver Control Signals
        4. 8.3.1.4 Receiver Timing
      2. 8.3.2 Clocking and Timing Signal Generation
      3. 8.3.3 Timer Module
        1. 8.3.3.1 Using the Timer Module
      4. 8.3.4 Receiver Subsystem Power Path
      5. 8.3.5 Transmit Section
        1. 8.3.5.1 Third LED Support
        2. 8.3.5.2 Transmitter Power Path
        3. 8.3.5.3 LED Power Reduction During Periods of Inactivity
        4. 8.3.5.4 LED Configurations
    4. 8.4 Device Functional Modes
      1. 8.4.1 ADC Operation and Averaging Module
        1. 8.4.1.1 Operation Without Averaging
        2. 8.4.1.2 Operation With Averaging
        3. 8.4.1.3 Dynamic Power-Down Mode
      2. 8.4.2 Diagnostics
        1. 8.4.2.1 Photodiode-Side Fault Detection
        2. 8.4.2.2 Transmitter-Side Fault Detection
        3. 8.4.2.3 Diagnostics Module
    5. 8.5 Programming
      1. 8.5.1 Serial Programming Interface
      2. 8.5.2 Reading and Writing Data
        1. 8.5.2.1 Writing Data
        2. 8.5.2.2 Reading Data
        3. 8.5.2.3 Multiple Data Reads and Writes
        4. 8.5.2.4 Register Initialization
        5. 8.5.2.5 AFE SPI Interface Design Considerations
    6. 8.6 Register Maps
      1. 8.6.1 AFE Register Map
      2. 8.6.2 AFE Register Description
  9. 9 Application Information Disclaimer
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Power Consumption Considerations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.5.4 LED Configurations

Multiple LED configurations are possible with the AFE4403.

Case 1: Red, IR LEDs in the common anode configuration for SPO2 and a Green LED for the HRM. Figure 8-21 shows the common anode configuration for this case. Figure 8-22 shows the configuration for HRM mode.

GUID-DB34F066-B91D-474F-82E0-7C1B59408D66-low.gifFigure 8-21 SPO2 Application, Common Anode Configuration

HRM mode: Set TX3_MODE = 1.

GUID-28363C1B-7B76-44B4-9276-199D45E09844-low.gifFigure 8-22 HRM Application Using the Third LED (Optional use of the IR LED)

Case 2: Red, IR LEDs in an H-bridge configuration for SPO2 and a Green LED for the HRM. The H-bridge configuration for this case is shown in Figure 8-23. Figure 8-24 shows the configuration for HRM mode.

SPO2 mode: Set TX3_MODE = 0.

GUID-40D1DC49-BA08-494E-ADD9-6C1AA8D35485-low.gifFigure 8-23 SPO2 Application, H-Bridge Configuration

HRM mode: Set TX3_MODE = 1.

GUID-C055679F-5457-4323-8A86-4276F4F0CFEE-low.gifFigure 8-24 HRM Application Using the Third LED

Case 3: Driving two LEDs simultaneously for HRM.

Some sensor modules have two LEDs on either side of the photodiode to make the illumination more uniform. The two LEDs can be connected in parallel, as shown in Figure 8-25.

The connection shown in Figure 8-25 results in an equal split of the current between the two LEDs if their forward voltages are exactly matched. High mismatch in the forward voltages of the two LEDs can cause one of them to consume the majority of the current.

GUID-5FD923B2-D0E7-4FF9-B253-52CD828509CA-low.gifFigure 8-25 Using Two Parallel LEDs for an HRM Application

Case 4: Driving two LEDs separated in time for HRM.

The two LEDs can also be driven as shown in Figure 8-26.

While this mode of driving the two LEDs does not drive them simultaneously, there are two advantages in this case. First, the full current is available for driving each LED. Secondly, the mismatch in the forward voltages between the two LEDs does not play a role.

GUID-FBD05DC7-8476-43EB-AFF8-E8D0F1B6BF14-low.gifFigure 8-26 Using Two Parallel LEDs for an HRM Application with Separation in Timing