AFE4420 Ultra-small integrated AFE with FIFO for multisensor wearable optical heart-rate monitoring |

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Ultra-small integrated AFE with FIFO for multisensor wearable optical heart-rate monitoring


Recommended alternative parts

  • AFE4405  - The device has SIMILAR FUNCTIONALITY but is not functionally equivalent to the compared device. 

More Information

Full data sheet and other design resources are available under NDA. Request now


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.


  • 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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Compare all products in Biosensing AFEs Email Download to Excel
Part number Order Number of 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 Order now 4     24     I2C     4     Optical Biosensing     -40 to 85         4.10 | 1ku    
AFE4404 Order now 1     24     I2C     3     Optical biosensing     -20 to 70     DSBGA | 15     See datasheet (DSBGA)     2.28 | 1ku    
AFE4405 Samples not available 2     24     I2C
3     Optical biosensing     -20 to 70         2.50 | 1ku    
AFE4410 Samples not available 3     24     SPI
4     Optical biosensing     -20 to 70         2.65 | 1ku