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SP19436-Overview of PPG LEDs and sensors

Apple Watch 4’s PPG and ECG Health Sensors

Product code
EUR 6990
Medical Mobile & Consumer
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The first FDA approved multi-million produced Smart Watch for consumer market.

The  medical wearable market is forecasted to become worth an impressive $32B by 2024. We see a convergence of needs, where healthcare costs must fall, IT telecommunication is being deployed and patients want to be involved in monitoring their health. This convergence accelerates the demand for medical-grade wearables. The Apple Watch series 4 targets these needs as the first mass-produced consumer accessory receiving FDA approval for its ElectroCardioGram (ECG).

SP19436-Apple Watch Backside with ECG electrodes

The two main health sensors in the Apple Watch series 4 are an enhanced PhotoPlethysmoGram (PPG) and, for the first time in an Apple watch, an ECG.

The PPG is the core of the continuous heart beat sensor. A new, more compact, design reduces the surface area by 30%, while the number of components decreases from 14 to six. This enhances heartbeat measures. OSRAM supplies the watch’s green LEDs, and you can discover other component suppliers in the report.

The ECG electrically measures very small currents using three electrodes. Two wrist electrodes are integrated on the back side of the watch. The third electrode is in the digital crown. The signals are captured and amplified by Analog Devices circuits.

This report constitutes a thorough analysis of the Apple Watch 4’s health sensors and the back optical window. The electronic components are standard and can be readily found in the market. However, their integration and the optical window are unique to Apple. Apple has fully redesigned its watch to integrate more efficient health sensors. The report studies exactly how the sensors are integrated.

This report also analyzes the complete health sensor system, including a full analysis of the infrared LED from Epistar, green LEDs from OSRAM and the photodiodes from OSRAM for the PPG. For the ECG sensor, the integrated circuits and the three electrodes are also studied in the report. Moreover, the back window’s specific lenses, optical system and electrodes are analyzed.

Additionally, the report includes a physical and technical comparison with the PPG components present in the first Apple watches.

SP19436-Overview of PPG LEDs and sensorsSP19436-PPG PhotodiodeSP19436-ECG sensor IC
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  • Executive Summary
  • Reverse Costing Methodology

Company Profile

  • Apple
  • Apple Watch 4
  • Analog Devices

Physical Analysis

  • Summary of the Physical Analysis
  • Apple Watch 4 Teardown
  • ECG Module Assembly
    • Module views
    • Electrodes
  • ECG Analog Front End
    • IC die view and dimensions
    • IC delayering and main blocks
    • IC die process, cross-section
    • IC die process characteristic
  • PPM Module Assembly
    • Module views and cross-sections
    • Die overview and dimensions
    • Die process and cross-section and process characteristics
  • PPG Green LED
  • PPG Photodiode
    • Die view and dimensions, process and cross-section
    • Die process characteristic
  • Comparison of PPG Function between Apple Watch 3 and 4

Manufacturer Process

  • Analog Front End Component
  • IR and Green LED
  • Photodiodes
  • Sapphire Window

Cost Analysis

  • Yield Hypothesis
  • ECG Sensor IC
  • Sensor Component Cost
  • PPG IR LED Component Cost
  • PPG Green LED Component cost
  • PPG Photodiode Component cost
  • Sapphire Window Cost


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