AFE4900 Datasheet, PDF (1/10 Pages) Texas Instruments – Ultra-Low Power, Integrated AFE for Wearable Optical, Electrical Bio-Sensing With FIFO

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AFE4900 Ultra-Low Power, Integrated AFE for
Wearable Optical, Electrical Bio-Sensing With FIFO
AFE4900
SBAS861 – AUGUST 2017
1 Features
•1 Synchronized PPG, ECG Signal Acquisition at
Data Rates Up to 1 kHz
• ECG Signal Chain:
– Standalone ECG Acquisition Up to 4 kHz
– Input Bias: 1-Lead ECG With RLD Bias
– Programmable INA Gain: 2 to 12
– Input Noise (1 Hz to 150 Hz): 2.5 µVrms at
1 kHz, 1.25 µVrms at 4-kHz Data Rate
– AC, DC Lead-Off Detect: 12.5-nA to 100-nA
• PPG Receiver:
– Supports Three Time-Multiplexed PD Inputs
– 24-Bit Representation of Current From PD
– DC Offset Subtraction DAC (Up to ±126-µA) at
TIA Input for Each LED, Ambient
– Digital Ambient Subtraction at ADC Output
– Noise Filtering With Programmable Bandwidth
– Transimpedance Gain: 10 kΩ to 2 MΩ
– Dynamic Range Up to 100 dB
– Receiver Operates in PPG-Only mode at
Approximately 1-μA/Hz Sampling Rate
– Power-Down Mode: Approximately 0 μA
• PPG Transmitter:
– Four LEDs in Common Anode Configuration
– 8-Bit LED Current Up to 200 mA
– Mode to Fire Two LEDs in Parallel
– Programmable LED On-Time
– Simultaneous Support of Three LEDs for
SpO₂, or Multiwavelength HRM
– Average Current of 30 μA Adequate for a
Typical Heart-Rate Monitoring Scenario:
– 20-mA Setting, 60-μs Pulse Duration,
25-Hz Sampling Rate
• Clocking Using an External or Internal Clock
• FIFO With 128-Sample Depth for ECG and PPG
• I²C, SPI^™ Interfaces: Selectable by Pin
• Operating Temperature Range: –20°C to +70°C
• 2.6-mm × 2.1-mm, 0.4-mm Pitch DSBGA Package
• Supplies:
– Rx: 1.8 V to 1.9 V (LDO Bypass),
2.0 V to 3.6 V (LDO Enabled)
– Tx: 3 V to 5.25 V
– IO: 1.7 V to Rx_SUP
2 Applications
• Synchronized PPG, ECG for Blood Pressure
Estimation
• HRM for Wearables, Hearables
• Heart-Rate Variability (HRV)
• Pulse Oximetry (SpO₂) Measurements
3 Description
The AFE4900 device is an analog front-end (AFE) for
synchronized
electrocardiogram
(ECG),
photoplethysmogram (PPG) signal acquisition. The
device can also be used for optical bio-sensing
applications, such as heart-rate monitoring (HRM)
and saturation of peripheral capillary oxygen (SpO₂).
The PPG signal chain supports up to four switching
light-emitting diodes (LEDs) and up to three
photodiodes (PDs). The LEDs can be switched on
using a fully integrated LED driver. The current from
the photodiode is converted into voltage by the
transimpedance amplifier (TIA) and digitized using an
analog-to-digital converter (ADC). The ECG signal
chain has an instrumentation amplifier (INA) with a
programmable gain that interfaces to the same ADC.
A right-leg drive (RLD) amplifier set can be used to
the bias for the ECG input pins. AC and dc lead-off
detect schemes are supported. The ADC codes from
the PPG and ECG phases can be stored in a 128-
sample first in, first out (FIFO) block and read out
using either an I²C or a serial programming interface
(SPI) interface.
Device Information⁽¹⁾
PART NUMBER PACKAGE
BODY SIZE (NOM)
AFE4900
DSBGA (30)
2.60 mm × 2.10 mm
(1) For all available packages, see the package option addendum
at the end of the datasheet.
SPACE
Simplified Block Diagram
PD1
PD2
PD3
INP1
INM1
INP2
INM2
INP3
INM3
INP_ECG
INM_ECG
RLD_OUT
Offset DAC
Cf
Rf
TIA
Rf
Cf
INA
AC/DC
Lead-off
Detect
RX_SUP
CONTROL1
TX_SUP
TX_ SUP
LED1
LED2
LED3
LED4
TX1
TX2
TX3
TX4
1.8-V LDOs
ALDO_1V8, DLDO_1V8
Noise Reduction
filter (x4)
ADC
ILED
Decimation
Threshold
Detection
FIFO
THR_DET_RDY
SPI/
I2C Interface
4 MHz
Oscillator
ENABLE_PTT
Timing Engine
128 kHz
Oscillator
I2C_SPI_SEL
SPI
I2C
RESETZ
ADC_RDY
PROG_OUT1
CLK
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.