Product details

Applications Optical-HRM Number of input channels 4 Resolution (Bits) 24 Number of LEDs 4 Interface type I2C Operating temperature range (C) -40 to 85
Applications Optical-HRM Number of input channels 4 Resolution (Bits) 24 Number of LEDs 4 Interface type I2C Operating temperature range (C) -40 to 85
  • 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
  • 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

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.

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.

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Technical documentation

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Type Title Date
* Data sheet AFE4420 Ultra-Small, Integrated AFE With FIFO for Multi-sensor Wearable, Optical Heart-rate Monitoring and Bio-sensing datasheet (Rev. A) 30 Jul 2019
Technical article Designing compact, efficient and high performing multiparameter patient monitors 25 Jun 2019
Technical article Going beyond traditional SpO2 measurement with multiwavelength optical measurements 12 Feb 2019
Technical article Offset correction improves the next generation of heart-rate smart watches 24 Aug 2015
Technical article A new way to illuminate the human condition 30 Dec 2013

Design & development

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Evaluation board

AFE4420EVM — AFE4420 integrated AFE with FIFO for wearable optical heart-rate monitoring evaluation module

The AFE4420 evaluation module (EVM) is a platform for evaluating the AFE4420 device, which is an analog front end (AFE) for optical biosensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). AFE4420 supports four switching (...)

Simulation tool

PSPICE-FOR-TI — PSpice® for TI design and simulation tool

PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
Reference designs

TIDA-010029 — Wearable, 16-phase multi-sensor SpO2 and heart rate monitor (HRM) reference design with Bluetooth® 5

This reference design enables a wearable, optimized saturation of peripheral capillary oxygen (SpO2) and multi-sensor, multi-wavelength optical heart rate monitor (HRM). It uses AFE4420 device, which is a single-chip, bio-sensing front end for photoplethysmography (PPG) measurements. It supports up (...)
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