1 Features
• Supports simultaneous and synchronized
acquisition of up to 24 PPG and a single-lead ECG
signal.
• Flexible allocation of 8 LED, 4 PD in each phase
• ECG signal chain:
– 1-lead ECG signal acquisition up to 2 kHz
– RLD output to drive a third electrode
– Input noise : 0.7 μV-rms
– Supports up to ±0.65 V differential DC offset
and +/-0.55 V common mode range
– Programmable INA gain: 11, 21
– High-pass filter with quick saturation recovery
– Integrated 300 Hz anti-aliasing low pass filter
– AC, DC lead-off detect: 2.9 nA to 92.5 nA
– Low power continuous lead-on detection
• Impedance signal chain
– Continuous low-power monitoring of impedance
between 2 electrodes
– 7 MΩ range
– 300 Ω noise on 620 kΩ
• PPG Transmitter:
– 8-Bit Programmable LED Current with range
adjustable from 25 mA to 250 mA
– Mode to fire two LEDs in parallel
– Support of 8 LEDs in Common Anode
configuration for SpO2, Multi-Wavelength HRM
• PPG Receiver:
– 2 parallel receivers (two sets of TIA/ filter)
– Supports 4 Time-Multiplexed Photodiode Inputs
to each Receiver
– 8-bit Ambient Offset subtraction at each TIA
input with 256 μA range
– 8-bit LED Offset Subtraction DAC with 64 μA
range
– Automatic ambient cancellation and dynamic
LED DC cancellation at TIA input
– Ambient rejection close to 100 dB up to 10 Hz
– Noise filtering with programmable bandwidth
– Trans-impedance Gain: 3.7 kΩ to 1 MΩ
• Accurate, Continuous Heart-Rate Monitoring:
– System SNR up to 109-dB at 16 μA PD current
– Low Current for Continuous Operation on a
Wearable Device with a Typical Value: 15-μA
for an LED, 20-μA for the Receiver
• External clock and internal oscillator modes
• Acquire data synchronized with system master
clock
• FIFO with 256-sample Depth
• SPI, I2C interfaces: Selectable by pin
• 2.6-mm × 2.5-mm DSBGA, 0.4-mm Pitch
• Supplies: Rx:1.7-1.9V (LDO Bypass); 1.9-3.6V
(LDO Enabled), Tx:3-5.5V, IO:1.7-RX_SUP

2 Applications
• Optical Heart-Rate Monitoring (HRM) for
Wearables, Hearables
• High performance ECG signal acquisition
• Synchronized PPG, ECG for BP estimation
• Heart-rate variability (HRV)
• Pulse oximetry (SpO2) measurements

3 Description
The AFE4950 device is an analog front-end (AFE)
for synchronized signal acquisition of PPG and ECG
signals. The device can also be used for optical biosensing
applications, such as heart-rate monitoring
(HRM) and saturation of peripheral capillary oxygen
(SpO2). The ECG signal chain supports 2- and 3-
electrode configurations and has an integrated Right
leg drive (RLD) buffer. The ECG signal chain can also
be used to do a continuous, low-power monitoring of
the impedance between pair of electrodes.