The AFE4404 is an analog front-end (AFE) for optical bio-sensing applications, such as heart-rate monitoring (HRM) and saturation of peripheral capillary oxygen (SpO2). The device supports three switching light-emitting diodes (LEDs) and a single photodiode. The current from the photodiode is converted into voltage by the transimpedance amplifier (TIA) and digitized using an analog-to-digital converter (ADC). The ADC code can be read out using an I2C interface. The AFE also has a fully-integrated LED driver with a 6-bit current control. The device has a high dynamic range transmit and receive circuitry that helps with the sensing of very small signal levels.
● Transmitter:
● Supports Common Anode LED Configuration
● Dynamic Range: 100 dB
● 6-Bit Programmable LED Current to 50 mA (Extendable to 100 mA)
● Programmable LED On-Time
● Simultaneous Support of 3 LEDs for Optimized SPO2, HRM, or Multi-Wavelength HRM
● Receiver:
● 24-Bit Representation of the Current Input from a Photodiode in Twos Complement Format
● Individual DC Offset Subtraction DAC at TIA Input for Each LED and Ambient Phase
● Digital Ambient Subtraction at ADC Output
● Programmable Transimpedance Gain:
●10 kΩ to 2 MΩ
● Dynamic Range: 100 dB
● Average Current Less Than 200 µA for PPG Signal Acquisition
● Pulse Frequency: 10 SPS to 1000 SPS
● Flexible Pulse Sequencing and Timing Control
● Flexible Clock Options:
● External Clocking:
●4-MHz to 60-MHz Input Clock
● Internal Clocking: 4-MHz Oscillator
● I2C Interface
● Operating Temperature Range: –20°C to 70°C
● 2.6-mm × 1.6-mm DSBGA Package, 0.5-mm Pitch
● Supplies: Rx: 2 V to 3.6 V, Tx: 3 V to 5.25 V,
●IO: 1.8 V to 3.6 V
