Texas Instruments AFE4460 Manual

AFE4460 Ultra-Small, Integrated AFE for Optical Bio-Sensing
1 Features
• Supports signal acquisition of up to 16 phase sets
• Supports up to 32 LEDs, 4 PDs
• Flexible allocation of LEDs, PDs in each phase
• Simultaneous signal acquisition from different
sensors at different data rates
• Accurate, continuous PPG monitoring:
– Low current for continuous heart-rate
monitoring on a wearable device with a typical
value: 15 μA for an LED, 15 μA for the receiver
– Peak system SNR of 115 dB
• Transmitter:
– 8-Bit Programmable LED current with range
adjustable from 25 mA to 250 mA
– Mode to fire two LEDs in parallel with
independent per-phase current control
– Programmable LED on-time per-phase
– Simultaneous support of 32 LEDs for SpO2,
Multi-Wavelength HRM, and Spectroscopy
• Receiver:
– Supports 4 Time-Multiplexed PD Inputs
– 4 parallel receivers (4 sets of TIA/filter)
– Individual ambient offset subtraction DAC at
each TIA Input with 8-bit per-phase control and
range adjustable up to 255-µA
– Individual LED offset subtraction DAC at each
TIA input with 9-bit per-phase control and 64-
µA range
– Digital ambient subtraction at ADC output
– Noise filtering with programmable bandwidth
– Transimpedance gain: 3.7 kΩ to 1 MΩ
• Supports external clock or internal oscillator
• Option to acquire data synchronized with a system
clock
• Automatic cancellation of DC from Ambient, LED
• FIFO with 256-sample depth
• SPI™ interface/ I2C interface
• 2.6-mm × 2.6-mm DSBGA, 0.4-mm Pitch
• Supplies: Rx:1.7 - 1.9 V (LDO Bypass); 1.9 - 3.6 V
(LDO Enabled), Tx: 3-5.5 V, IO: 1.7-RX_SUP
2 Applications
• Optical Heart-Rate Monitoring (HRM) for
wearables, hearables
• Heart-Rate Variability (HRV)
• Pulse Oximetry (SpO2) measurements
• Optical Spectroscopy
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.
3 Description
The AFE4460 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 32 switching light-
emitting diodes (LEDs) and up to four photodiodes
(PDs). The AFE has two LED drivers each with 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. Up to 16
signal phase sets can be defined, each phase
set comprising a combination of LED and Ambient
phases. Low noise offset DACs at the receiver inputs
can be automatically controlled to cancel DC from
Ambient and LED light. The current from each of
the 4 PDs in each phase is converted into voltage
by TIAs, filtered, and then digitized using a common
ADC. The ADC code can be stored in a 256-sample
FIFO block. The FIFO can be read out using a SPI or
2
I C interface.
Device Information
PART NUMBER PACKAGE
AFE4460 DSBGA (36)
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
TX_SUP TXN1 TXN2 TXN3 TXN4 TXN5 TXN6 TXN7
TI Gray Alternate
LED_DRV2
LED_DRV1
INP1
INM1
Cf1
INP2 Rf1
INM2
+
TIA1 Reduction
TI Gray Alternate
–
INP3
INM3
Rf1
Cf1
INP4
AACM
INM4
4 PPG RX Channels
AFE4460
SBASAL6 – JUNE 2022
(1)
BODY SIZE (NOM)
2.60 mm × 2.60 mm
TXN8 TXP1 TXP2 TXP3 TXP4
VDD_INT
LDO
TX_SUP
SPI, I2C
SPI, I2C
FIFO
M
Noise Processing,
U ADC
Decimation
X
Filter
Filters
ADC_RDY
8 MHz Timing
GPIO
Oscillator Engine
256 kHz
Oscillator
CLK