AFE4900YZR

The AFE4900 device is an analog front - end (AFE) for synchronous electrocardiogram (ECG) and photoplethysmogram (PPG) signal acquisition. This device can also be used in optical biosensing applications, such as heart rate monitoring (HRM) and peripheral capillary oxygen saturation (SpO₂) measurement. The PPG signal chain supports up to four switchable light - emitting diodes (LEDs) and up to three photodiodes (PDs). The LEDs can be turned on using a fully integrated LED driver. The current of the photodiodes is converted to voltage through a transimpedance amplifier (TIA) and digitized using an analog - to - digital converter (ADC). The ECG signal chain has an instrumentation amplifier (INA) with programmable gain connected to the same ADC. A right - leg drive (RLD) amplifier group can be used to bias the ECG input pins. Both AC and DC lead - off detection 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 using the I²C or serial peripheral interface (SPI).

Applications

• Synchronous PPG & ECG for blood pressure estimation
• HRM (wearables and smart hearables)
• Heart rate variability (HRV) analysis
• Pulse oximetry (SpO₂) measurement

Key features

• Synchronous PPG and ECG signal acquisition at data rates up to 1kHz
• ECG signal chain:
• Standalone ECG acquisition up to 4kHz
• Input bias: single-lead ECG with RLD bias
• Programmable INA gain: 2.15 to 12.92
• Input noise (1Hz to 150Hz): 2.5μVrms at 1kHz data rate, 1.25μVrms at 4kHz data rate
• AC/DC lead-off detection: 12.5nA to 100nA
• IEC 60601 test report applied for
• PPG receiver:
• Supports three time-division multiplexed PD inputs
• 24-bit representation of current from PD
• DC offset cancellation DAC at TIA input (up to ±126μA) for each LED and ambient
• Digital ambient cancellation at ADC output
• Noise filter with programmable bandwidth
• Transimpedance gain: 10kΩ to 2MΩ
• Dynamic range up to 100dB
• Receiver operates at approximately 1μA/Hz sample rate in PPG-only mode
• Power-down mode: approximately 0μA
• PPG transmitter:
• Four LEDs in common-anode configuration
• 8-bit LED current up to 200mA
• Mode for simultaneously driving two LEDs
• Programmable LED on-time
• Simultaneous support for three LEDs for SpO₂ or multi-wavelength HRM
• Average current 30μA for typical heart rate monitoring: 20mA setting, 60μs pulse duration, 25Hz sample rate
• Timing using external or internal clock
• FIFO with 128-sample depth for ECG and PPG
• I²C and SPI interfaces: pin-selectable
• Power supply:
• Rx: 1.8V to 1.9V (LDO bypass), 2.0V to 3.6V (LDO enabled)
• Tx: 3V to 5.25V
• IO: 1.7V to Rx_SUP