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  • AFE4404 Ultra-Small, Integrated AFE for Wearable, Optical, Heart-Rate Monitoring and Bio-Sensing

    • SBAS689D June   2015  – December 2016 AFE4404

      PRODUCTION DATA.  

  • CONTENTS
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  • AFE4404 Ultra-Small, Integrated AFE for Wearable, Optical, Heart-Rate Monitoring and Bio-Sensing
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 TIA and Switched RC Filter
        1. 8.3.1.1 Operation with Two and Three LEDs
          1. 8.3.1.1.1 LED Current Setting
        2. 8.3.1.2 TIA Gain Settings
        3. 8.3.1.3 TIA Bandwidth Settings
      2. 8.3.2 Power Management
        1. 8.3.2.1 Transmitter Supply (TX_SUP)
        2. 8.3.2.2 Receiver Supply (RX_SUP)
        3. 8.3.2.3 I/O Supply (IO_SUP)
        4. 8.3.2.4 Boost Converters Selection
      3. 8.3.3 Offset Cancellation DAC
        1. 8.3.3.1 Offset Cancellation DAC Controls
      4. 8.3.4 Analog-to-Digital Converter (ADC)
      5. 8.3.5 I2C Interface
      6. 8.3.6 Timing Engine
        1. 8.3.6.1 Timer and PRF Controls
        2. 8.3.6.2 Timing Control Registers
        3. 8.3.6.3 Receiver Timing
        4. 8.3.6.4 Dynamic Power-Down Timing
        5. 8.3.6.5 Sample Register Values
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power Modes
      2. 8.4.2 RESET Modes
      3. 8.4.3 Clocking Modes
      4. 8.4.4 PRF Programmability
      5. 8.4.5 Averaging Modes
      6. 8.4.6 Decimation Mode
        1. 8.4.6.1 Decimation Mode Power and Performance
    5. 8.5 Register Map
      1. 8.5.1  Register 0h (address = 0h) [reset = 0h]
      2. 8.5.2  Register 1h (address = 1h) [reset = 0h]
      3. 8.5.3  Register 2h (address = 2h) [reset = 0h]
      4. 8.5.4  Register 3h (address = 3h) [reset = 0h]
      5. 8.5.5  Register 4h (address = 4h) [reset = 0h]
      6. 8.5.6  Register 5h (address = 5h) [reset = 0h]
      7. 8.5.7  Register 6h (address = 6h) [reset = 0h]
      8. 8.5.8  Register 7h (address = 7h) [reset = 0h]
      9. 8.5.9  Register 8h (address = 8h) [reset = 0h]
      10. 8.5.10 Register 9h (address = 9h) [reset = 0h]
      11. 8.5.11 Register Ah (address = Ah) [reset = 0h]
      12. 8.5.12 Register Bh (address = Bh) [reset = 0h]
      13. 8.5.13 Register Ch (address = Ch) [reset = 0h]
      14. 8.5.14 Register Dh (address = Dh) [reset = 0h]
      15. 8.5.15 Register Eh (address = Eh) [reset = 0h]
      16. 8.5.16 Register Fh (address = Fh) [reset = 0h]
      17. 8.5.17 Register 10h (address = 10h) [reset = 0h]
      18. 8.5.18 Register 11h (address = 11h) [reset = 0h]
      19. 8.5.19 Register 12h (address = 12h) [reset = 0h]
      20. 8.5.20 Register 13h (address = 13h) [reset = 0h]
      21. 8.5.21 Register 14h (address = 14h) [reset = 0h]
      22. 8.5.22 Register 15h (address = 15h) [reset = 0h]
      23. 8.5.23 Register 16h (address = 16h) [reset = 0h]
      24. 8.5.24 Register 17h (address = 17h) [reset = 0h]
      25. 8.5.25 Register 18h (address = 18h) [reset = 0h]
      26. 8.5.26 Register 19h (address = 19h) [reset = 0h]
      27. 8.5.27 Register 1Ah (address = 1Ah) [reset = 0h]
      28. 8.5.28 Register 1Bh (address = 1Bh) [reset = 0h]
      29. 8.5.29 Register 1Ch (address = 1Ch) [reset = 0h]
      30. 8.5.30 Register 1Dh (address = 1Dh) [reset = 0h]
      31. 8.5.31 Register 1Eh (address = 1Eh) [reset = 0h]
      32. 8.5.32 Register 20h (address = 20h) [reset = 0h]
      33. 8.5.33 Register 21h (address = 21h) [reset = 0h]
      34. 8.5.34 Register 22h (address = 22h) [reset = 0h]
      35. 8.5.35 Register 23h (address = 23h) [reset = 0h]
      36. 8.5.36 Register 29h (address = 29h) [reset = 0h]
      37. 8.5.37 Register 2Ah (address = 2Ah) [reset = 0h]
      38. 8.5.38 Register 2Bh (address = 2Bh) [reset = 0h]
      39. 8.5.39 Register 2Ch (address = 2Ch) [reset = 0h]
      40. 8.5.40 Register 2Dh (address = 2Dh) [reset = 0h]
      41. 8.5.41 Register 2Eh (address = 2Eh) [reset = 0h]
      42. 8.5.42 Register 2Fh (address = 2Fh) [reset = 0h]
      43. 8.5.43 Register 31h (address = 31h) [reset = 0h]
      44. 8.5.44 Register 32h (address = 32h) [reset = 0h]
      45. 8.5.45 Register 33h (address = 33h) [reset = 0h]
      46. 8.5.46 Register 34h (address = 34h) [reset = 0h]
      47. 8.5.47 Register 35h (address = 35h) [reset = 0h]
      48. 8.5.48 Register 36h (address = 36h) [reset = 0h]
      49. 8.5.49 Register 37h (address = 37h) [reset = 0h]
      50. 8.5.50 Register 39h (address = 39h) [reset = 0h]
      51. 8.5.51 Register 3Ah (address = 3Ah) [reset = 0h]
      52. 8.5.52 Register 3Dh (address = 3Dh) [reset = 0h]
      53. 8.5.53 Register 3Fh (address = 3Fh) [reset = 0h]
      54. 8.5.54 Register 40h (address = 40h) [reset = 0h]
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 System-Level ESD Considerations
        2. 9.2.2.2 Reducing Sensitivity to Ambient Light Modulation
      3. 9.2.3 Application Curves
        1. 9.2.3.1 Choosing the Right AFE Settings
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information
  14. IMPORTANT NOTICE

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • YZP|15
Thermal pad, mechanical data (Package|Pins)
Orderable Information
  • sbas689d_oa
  • sbas689d_pm
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DATA SHEET

AFE4404 Ultra-Small, Integrated AFE for Wearable, Optical, Heart-Rate Monitoring and Bio-Sensing

1 Features

  • Transmitter:
    • Supports Common Anode LED Configuration
    • Dynamic Range: 100 dB
    • 6-Bit Programmable LED Current to 50 mA (Extendable to 100 mA)
    • Programmable LED On-Time
    • Simultaneous Support of 3 LEDs for Optimized SpO2, HRM, or Multi-Wavelength HRM
  • Receiver:
    • 24-Bit Representation of the Current Input from a Photodiode in Twos Complement Format
    • Individual DC Offset Subtraction DAC at TIA Input for Each LED and Ambient Phase
    • Digital Ambient Subtraction at ADC Output
    • Programmable Transimpedance Gain:
      10 kΩ to 2 MΩ
    • Dynamic Range: 100 dB
    • Average Current Less Than 200 μA for PPG Signal Acquisition
  • Pulse Frequency: 10 SPS to 1000 SPS
  • Flexible Pulse Sequencing and Timing Control
  • Flexible Clock Options:
    • External Clocking:
      4-MHz to 60-MHz Input Clock
    • Internal Clocking: 4-MHz Oscillator
  • I2C Interface
  • Operating Temperature Range: –20°C to 70°C
  • 2.6-mm × 1.6-mm DSBGA Package, 0.5-mm Pitch
  • Supplies: Rx: 2 V to 3.6 V, Tx: 3 V to 5.25 V,
    IO: 1.8 V to 3.6 V

2 Applications

  • Optical Heart-Rate Monitoring (HRM)
  • Heart-Rate Variability (HRV)
  • Pulse Oximetry (SpO2 Measurement)
  • VO2 Max
  • Calorie Expenditure

3 Description

The AFE4404 is an analog front-end (AFE) for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports three switching light-emitting diodes (LEDs) and a single photodiode. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and digitized using an analog-to-digital converter (ADC). The ADC code can be read out using an I2C interface. The AFE also has a fully-integrated LED driver with a 6-bit current control. The device has a high dynamic range transmit and receive circuitry that helps with the sensing of very small signal levels.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
AFE4404 DSBGA (15) 2.60 mm × 1.60 mm(2)
  1. For all available packages, see the orderable addendum at the end of the datasheet.
  2. Refers to dimensions D × E in Figure 99.

Simplified Block Diagram

AFE4404 frontpage_sbas689.gif

4 Revision History

Changes from C Revision (May 2016) to D Revision

  • Changed last sub-bullet of Receiver Features bullet Go
  • Changed test conditions of dynamic power-down mode rows in Current Consumption subsection of Electrical Characteristics tableGo

Changes from B Revision (October 2015) to C Revision

  • Changed specifications of t1 and t4 rows in Table 7 to improve rejection of ambient lightGo
  • Changed Description column in Table 10 Go
  • Changed Table 11Go
  • Changed Table 12Go
  • Added Reducing Sensitivity to Ambient Light Modulation sectionGo

Changes from A Revision (August 2015) to B Revision

  • Changed TX_SUP pin number to E3 in Pin Functions table Go
  • Added Figure 9Go
  • Added Decimation Mode section Go
  • Added rows 3Dh, 3Fh, and 40h to Table 16Go
  • Added Register 3Dh description to Register Map sectionGo
  • Added Register 3Fh and Register 40h descriptions to Register Map sectionGo
  • Added System-Level ESD Considerations section Go
  • Added input-referred current paragraph associated to Figure 9 in Application Curves sectionGo

Changes from * Revision (June 2015) to A Revision

  • Deleted Diagnostics Mode sectionGo
  • Changed bit 2 of address 00h to 0 in Table 16 Go
  • Deleted row 30h from Table 16 Go
  • Changed bit 2 name and description in Register 0h Go
  • Deleted Register 30h Go

5 Device Comparison Table

PRODUCT PACKAGE-LEAD LED DRIVE CONFIGURATION LED DRIVE CURRENT
(mA, Max)		 OPERATING TEMPERATURE RANGE OPTIMIZED APPLICATION
AFE4400 VQFN-40 H-bridge,
common anode		 50 0°C to 70°C Finger-clip pulse oximeters
AFE4490 VQFN-40 H-bridge,
common anode		 200 –40°C to 85°C Clinical-grade pulse oximeters
AFE4403 DSBGA-36 H-bridge,
common anode		 100 –20°C to 70°C Clinical pulse oximeter patches, wearables
AFE4404 DSBGA-15 Common anode 50(1) –20°C to 70°C Wearable optical bio-sensing
(1) Mode that doubles the range to 100 mA with additional restrictions.

6 Pin Configuration and Functions

YZP Package
15-Ball DSBGA
Bottom View
AFE4404 po_sbas689.gif

Pin Functions

PIN I/O DESCRIPTION
NAME NO.
ADC_RDY B2 Digital ADC ready interrupt signal (output)
CLK C2 Digital Clock input or output, selectable based on register. Default is input (external clock mode). Can be set via a register to output the clock when the oscillator is enabled.(3)(2)
DNC C1 Do not connect (leave floating)
GND D3 Ground Common ground for transmitter and receiver
I2C_CLK E2 Digital I2C clock input, external pullup resistor to IO_SUP (for example, 10 kΩ)
I2C_DAT E1 Digital I2C data, external pullup resistor to IO_SUP (for example, 10 kΩ)
INM A1 Analog Connect only to anode of photodiode(1)
INP B1 Analog Connect only to cathode of photodiode(1)
IO_SUP A3 Supply Separate supply for digital I/O. Must be less than or equal to RX_SUP.
Can be tied to RX_SUP.
RESETZ D1 Digital RESETZ or PWDN: function based on (active low) duration of RESETZ pulse(4).
A 25-µs to 50-µs duration = RESETZ active.
A > 200-µs duration = PWDN active.
RX_SUP A2 Supply Receiver supply; 1-µF decapacitor to GND
TX1 B3 Analog Transmit output, LED1
TX2 D2 Analog Transmit output, LED2
TX3 C3 Analog Transmit output, LED3
TX_SUP E3 Supply Transmitter supply; 1-µF decapacitor to GND
(1) Maintain the indicated polarity of photodiode connections to the AFE input pins.
(2) In both hardware power-down (PWDN) and software power-down (PDNAFE) modes, the CLK pin is driven by the AFE to 0 V. Therefore, if operating in external clock mode, take care to shut off the external clock to the AFE when in these power-down modes.
(3) Depending on whether external clock mode or internal oscillator mode is used, extra series or shunt resistors are recommended on the CLK pin. For more details, see the Typical Application section.
(4) A RESET pulse must be applied after power-up to ensure that the registers are all reset to their default values.

 
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