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AFE4404
SBAS689D – JUNE 2015 – REVISED DECEMBER 2016
AFE4404 Ultra-Small, Integrated AFE for
Wearable, Optical, Heart-Rate Monitoring and Bio-Sensing
1 Features
1
2 Applications
•
•
•
•
•
Optical Heart-Rate Monitoring (HRM)
Heart-Rate Variability (HRV)
Pulse Oximetry (SpO2 Measurement)
VO2 Max
Calorie Expenditure
•
•
•
•
•
•
•
•
•
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
I
2
C 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
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 I
2
C 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
AFE4404
PACKAGE
DSBGA (15)
BODY SIZE (NOM)
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
TX_SUP
RX_SUP
Offset
Cancellation
DAC
LDO
I-V Amplifier (TIA)
C
f
ILED
TX_SUP
TX1
TX2
TX3
LED
Driver
IO_SUP
INP
R
f
Noise-
Reduction
Filter
R
f
Buffer
ADC
I
2
C Interface
IO
Buffer
I2C_CLK
I2C_DAT
RESETZ
INM
CLK
C
f
Internal,
External
Clock
Timing
Engine
GND
ADC_RDY
Copyright © 2016, Texas Instruments Incorporated
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
AFE4404
SBAS689D – JUNE 2015 – REVISED DECEMBER 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features
..................................................................
Applications
...........................................................
Description
.............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions
.........................
Specifications.........................................................
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ...............................................
Typical Characteristics ..............................................
1
1
1
2
4
4
6
6
6
6
6
7
8
9
8.3 Feature Description.................................................
14
8.4 Device Functional Modes........................................
29
8.5 Register Map...........................................................
33
9
Application and Implementation
........................
68
9.1 Application Information............................................
68
9.2 Typical Application ..................................................
68
10 Power Supply Recommendations
.....................
75
11 Layout...................................................................
77
11.1 Layout Guidelines .................................................
77
11.2 Layout Example ....................................................
77
12 Device and Documentation Support
.................
78
12.1
12.2
12.3
12.4
12.5
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
78
78
78
78
78
8
Detailed Description
............................................
13
8.1 Overview .................................................................
13
8.2 Functional Block Diagram .......................................
13
13 Mechanical, Packaging, and Orderable
Information
...........................................................
78
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (May 2016) to Revision D
•
•
Page
Changed last sub-bullet of
Receiver
Features bullet .............................................................................................................
1
Changed test conditions of
dynamic power-down mode
rows in
Current Consumption
subsection of
Electrical
Characteristics
table ...............................................................................................................................................................
8
Changes from Revision B (October 2015) to Revision C
•
•
•
•
•
Page
Changed specifications of t
1
and t
4
rows in Table 7 to improve rejection of ambient light...................................................
24
Changed
Description
column in Table 10 ...........................................................................................................................
26
Changed Table 11 ................................................................................................................................................................
27
Changed Table 12 ................................................................................................................................................................
28
Added
Reducing Sensitivity to Ambient Light Modulation
section........................................................................................
70
Changes from Revision A (August 2015) to Revision B
•
•
•
•
•
•
•
•
Page
Changed TX_SUP pin number to E3 in
Pin Functions
table .................................................................................................
5
Added
Figure 9
.....................................................................................................................................................................
10
Added
Decimation Mode
section .........................................................................................................................................
32
Added rows 3Dh, 3Fh, and 40h to
Table 16
........................................................................................................................
35
Added Register 3Dh description to
Register Map
section....................................................................................................
66
Added Register 3Fh and Register 40h descriptions to
Register Map
section......................................................................
67
Added
System-Level ESD Considerations
section .............................................................................................................
69
Added input-referred current paragraph associated to
Figure 9
in
Application Curves
section...........................................
72
2
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AFE4404
Copyright © 2015–2016, Texas Instruments Incorporated
AFE4404
www.ti.com
SBAS689D – JUNE 2015 – REVISED DECEMBER 2016
Changes from Original (June 2015) to Revision A
•
•
•
•
•
Page
Deleted
Diagnostics Mode
section .......................................................................................................................................
31
Changed bit 2 of address 00h to 0 in
Table 16
...................................................................................................................
33
Deleted row 30h from
Table 16
...........................................................................................................................................
34
Changed bit 2 name and description in
Register 0h
...........................................................................................................
36
Deleted
Register 30h
...........................................................................................................................................................
59
Copyright © 2015–2016, Texas Instruments Incorporated
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Product Folder Links:
AFE4404
3
AFE4404
SBAS689D – JUNE 2015 – REVISED DECEMBER 2016
www.ti.com
5 Device Comparison Table
PRODUCT
PACKAGE-LEAD
LED DRIVE
CONFIGURATION
H-bridge,
common anode
H-bridge,
common anode
H-bridge,
common anode
Common anode
LED DRIVE
CURRENT
(mA, Max)
50
200
100
50
(1)
OPERATING
TEMPERATURE
RANGE
0°C to 70°C
–40°C to 85°C
–20°C to 70°C
–20°C to 70°C
OPTIMIZED APPLICATION
AFE4400
AFE4490
AFE4403
AFE4404
VQFN-40
VQFN-40
DSBGA-36
DSBGA-15
Finger-clip pulse oximeters
Clinical-grade pulse oximeters
Clinical pulse oximeter patches, wearables
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
I2C_DAT
E
I2C_CLK
TX_SUP
RESETZ
D
TX2
GND
DNC
C
CLK
TX3
INP
B
ADC_RDY
TX1
INM
A
RX_SUP
IO_SUP
1
2
3
4
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AFE4404
Copyright © 2015–2016, Texas Instruments Incorporated
AFE4404
www.ti.com
SBAS689D – JUNE 2015 – REVISED DECEMBER 2016
Pin Functions
PIN
NAME
ADC_RDY
CLK
DNC
GND
I2C_CLK
I2C_DAT
INM
INP
IO_SUP
RESETZ
RX_SUP
TX1
TX2
TX3
TX_SUP
(1)
(2)
(3)
(4)
NO.
B2
C2
C1
D3
E2
E1
A1
B1
A3
D1
A2
B3
D2
C3
E3
Ground
Digital
Digital
Analog
Analog
Supply
Digital
Supply
Analog
Analog
Analog
Supply
I/O
Digital
Digital
ADC ready interrupt signal (output)
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.
(1) (2)
Do not connect (leave floating)
Common ground for transmitter and receiver
I
2
C clock input, external pullup resistor to IO_SUP (for example, 10 kΩ)
I
2
C data, external pullup resistor to IO_SUP (for example, 10 kΩ)
Connect only to anode of photodiode
(3)
Connect only to cathode of photodiode
(3)
Separate supply for digital I/O. Must be less than or equal to RX_SUP.
Can be tied to RX_SUP.
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.
Receiver supply; 1-µF decapacitor to GND
Transmit output, LED1
Transmit output, LED2
Transmit output, LED3
Transmitter supply; 1-µF decapacitor to GND
DESCRIPTION
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.
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.
Maintain the indicated polarity of photodiode connections to the AFE input pins.
A RESET pulse must be applied after power-up to ensure that the registers are all reset to their default values.
Copyright © 2015–2016, Texas Instruments Incorporated
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Product Folder Links:
AFE4404
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