AFE4420 Ultra-Small Integrated AFE With FIFO for Multisensor Wearable Optical Heart-Rate Monitoring | TI.com

AFE4420 (ACTIVE)

Ultra-Small Integrated AFE With FIFO for Multisensor Wearable Optical Heart-Rate Monitoring

Ultra-Small Integrated AFE With FIFO for Multisensor Wearable Optical Heart-Rate Monitoring - AFE4420
 

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Description

The AFE4420 is an analog front-end for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports up to four switching light-emitting diodes (LEDs) and up to four photodiodes. Up to 16 signal phases can be defined and the signal can be acquired from each phase in a synchronized manner and stored in a 128-sample First in, First out (FIFO) block. The FIFO can be read out using either an I2C or a SPI interface. The AFE also has a fully- integrated LED driver with an 8-bit current control. The device has a high dynamic range transmit-and- receive circuitry that helps with the sensing of very small signal levels.

Features

  • Supports Signal Acquisition of up to 16 Phases
  • Flexible Allocation of LEDs and PDs in Each Phase
  • Accurate, Continuous Heart-Rate Monitoring:
    • Up to 100-dB Dynamic Range
    • Low Current for Continuous Operation on a Wearable Device with a Typical Value
      • 15 µA for an LED, 20 µA for the Receiver
  • Transmitter:
    • Supports Common Anode LED Configuration
    • 8-Bit Programmable LED Current with Range Adjustable from 50 mA to 200 mA
    • Mode to Fire Two LEDs in Parallel
    • Programmable LED On-Time
    • Simultaneous Support of 4 LEDs for Optimized SpO2, HRM, or Multi-Wavelength HRM
    • Programmable Control Signals to Extend Operation to 8 LEDs using External SPDT Switches
  • Receiver:
    • Supports 4 Time-Multiplexed Photodiode Inputs
    • Individual DC Offset Subtraction DAC at TIA Input for each LED, Ambient with 7-bit Control and Range up to ±254 µA
    • Transimpedance Gain: 10 kΩ to 2 MΩ
    • Digital Ambient Subtraction at ADC Output to Suppress Ambient Tones
    • Noise Filtering with Programmable Bandwidth
  • Supports External Clock and Internal Oscillator Modes
  • Automatic Ambient Cancellation Mode (AACM) to Increase Receiver Dynamic Range
  • Two Programmable GPIO Pins with Flexible Interrupt Generation
  • FIFO with 128-sample Depth
  • I2C, SPI Interfaces: Selectable by Pin
  • Operating Temperature Range: –40°C to +85°C
  • 2.6-mm × 2.1-mm DSBGA, 0.4-mm Pitch
  • Supplies:
    • Rx:
      • 1.7 V to 1.9 V (LDO Bypass)
      • 1.9 V to 3.6 V (LDO Enabled)
    • Tx: 3 V to 5.5 V
    • IO: 1.7 V to RX_SUP

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Parametrics Compare all products in Biosensing AFEs

 
# Input Channels
Resolution (Bits)
Interface
Number of LEDs
Features
Operating Temperature Range (C)
Package Group
Package Size: mm2:W x L (PKG)
Approx. Price (US$)
AFE4420 AFE4404 AFE4405 AFE4410
4     1     2     3    
24     24     24     24    
I2C     I2C     I2C
SPI    
SPI
I2C    
  3     3     4    
Optical Biosensing     Optical biosensing     Optical biosensing     Optical biosensing    
-40 to 85     -20 to 70     -20 to 70     -20 to 70    
  DSBGA        
  See datasheet (DSBGA)        
4.10 | 1ku     2.28 | 1ku     2.50 | 1ku     2.65 | 1ku