AFE4950

• Supports simultaneous & 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: 2.6-nA to 85-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

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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 bio-sensing 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.