AFE4405 Datasheet, PDF (1/11 Pages) Texas Instruments – AFE4405 Ultra-Small, Integrated AFE with FIFO for Wearable, Optical Heart-Rate Monitoring and Bio-Sensing

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AFE4405
SBAS768B – APRIL 2016 – REVISED MAY 2016
AFE4405 Ultra-Small, Integrated AFE with FIFO for
Wearable, Optical Heart-Rate Monitoring and Bio-Sensing
1 Features
•1 Transmitter:
– Supports Common Anode LED Configuration
– Dynamic Range: 100 dB
– 8-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:
– Supports 2 Time-Multiplexed Photodiode
Inputs
– 24-Bit Representation of the Current Input from
the Photodiode in Twos Complement Format
– Individual DC Offset Subtraction DAC
(±15.75-µA Range) at TIA Input for Each LED,
Ambient
– Digital Ambient Subtraction at ADC Output
– Transimpedance Gain: 10 kΩ to 2 MΩ
– Dynamic Range: 100 dB
– Dynamic Power-Saving Mode to Reduce
Receiver Current to 200 µA
• Pulse Frequency: 5 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
• FIFO with 240 Sample Depth:
– Programmable Partitioning Across Phases
• I²C, SPI™ Interfaces: Selectable by Pin
• Operating Temperature Range: –20°C to +70°C
• 2.6-mm × 2.1-mm DSBGA, 0.4-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) for
Wearables, Hearables
• Heart-Rate Variability (HRV)
• Pulse Oximetry (SpO₂) Measurements
• Maximum Oxygen Consumption (VO₂ Max)
• Calorie Expenditure
3 Description
The AFE4405 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 up to two
photodiodes. 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 stored in a
240-sample first in, first out (FIFO) block with
programmable depth. The FIFO depth can be
partitioned to accommodate the phases that must be
stored. 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.
To request a full data sheet or other design
resources: request AFE4405
Device Information⁽¹⁾
PART NUMBER PACKAGE
BODY SIZE (NOM)
AFE4405
DSBGA (30)
2.60 mm × 2.10 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Block Diagram
RX_SUP
LED1
TX1
TX_SUP
LED2
TX2
LED3
TX3
TX_SUP
INP
PD1
INM
INP2
PD2
INM2
Offset
DAC
CF
LDO
RF
TIA
RF
Noise-
Reduction
+
Filter (x4)
CF
ADC
ILED
FIFO
SPI, I²C
Interface
Timing Engine
4-MHz Oscillator
I2C_SPI_SEL
SPI Interface
I²C Interface
RESETZ
ADC_RDY
PROG_OUT1
CLK
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.