AFE4403 - Ultra-Small Integrated Analog Front End (AFE) for Heart-Rate Monitors and Low-Cost Pulse Oximeters

The AFE4403 is a fully-integrated analog front-end (AFE) ideally suited for pulse oximeter applications. The device consists of a low-noise receiver channel with an integrated analog-to-digital converter (ADC), an LED transmit section, and diagnostics for sensor and LED fault detection. The device is a very configurable timing controller. This flexibility enables the user to have complete control of the device timing characteristics. To ease clocking requirements and provide a low-jitter clock to the AFE4403, an oscillator is also integrated that functions from an external crystal. The device communicates to an external microcontroller or host processor using an SPI™ interface.

The device is a complete AFE solution packaged in a single, compact DSBGA-36 (3.07 mm × 3.07 mm × 0.5 mm) and is specified over the operating temperature range of –20°C to 70°C.

• Fully-Integrated AFE for Pulse Oximeter and Heart Rate Monitoring Applications:
• Transmit:
  • Integrated Dual LED Driver
    (H-Bridge or Common Anode)
  • Option for a Third LED Support for Optimized SPO2, HRM, or Multi-Wavelength HRM
  • Up to 110-dB Dynamic Range
  • LED Current:
    • Programmable to 100 mA with 8-Bit Current Resolution
  • 30 µA + Average LED Current
  • Programmable LED On-Time
  • Independent LED2 and LED1 Current Reference
• Receive Channel with High Dynamic Range:
  • 22-Bit Output in Twos Complement Format
  • Up to 105-dB Dynamic Range
  • Low Power: < 650 µA
  • Dynamic Power-Down Mode to Reduce Current to 300 µA
  • Adaptable to a Very Wide Range of Signal Amplitudes:
    • Total Programmable Gain: 10 kΩ to 4 MΩ
  • Integrated Digital Ambient Estimation and Subtraction
• Flexible Clocking by External Clock or Crystal:
  • Pulse Frequency: 62.5 SPS to 2000 SPS
  • Flexible Pulse sequencing and Timing Control
  • Input Clock Range: 4 MHz (Min) to 60 MHz (Max)
• Integrated Fault Diagnostics:
  • Photodiode and LED Open and
    Short Detection
• Supplies:
  • Rx = 2.0 V to 3.6 V
  • Tx = 3.0 V to 5.25 V
• Package: Compact DSBGA-36
  (3.07 mm × 3.07 mm × 0.5 mm)
• Specified Temperature Range: –20°C to 70°C