AFE4420 Texas instruments

AFE4420

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AFE4420

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Описание

The AFE4420 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 four switching light-emitting diodes (LEDs) and up to four photodiodes. Up to 16 signal phases can be defined and the signal can be acquired from each phase in a synchronized manner and stored in a 128-sample First in, First out (FIFO) block. The FIFO can be read out using either an I2C or a SPI interface. The AFE also has a fully integrated LED driver with an 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.

Supports signal acquisition of up to 16 phases
Flexible allocation of LEDs and PDs in each phase
Accurate, continuous heart-rate monitoring:
- Up to 100-dB dynamic range
- Low current for continuous operation on a wearable device with a typical value
  - 15 µA for an LED, 20 µA for the receiver
Transmitter:
- Supports common anode LED configuration
- 8-Bit programmable LED current with range adjustable from 50 mA to 200 mA
- Mode to fire two LEDs in parallel
- Programmable LED on-time
- Simultaneous support of 4 LEDs for optimized SpO2, HRM, or multi-wavelength HRM
- Programmable control signals to extend operation to 8 LEDs using external SPDT switches
Receiver:
- Supports 4 time-multiplexed photodiode inputs
- Individual DC offset subtraction DAC at TIA input for each LED, ambient with 7-bit control and range up to ±254 µA
- Transimpedance gain: 10 kΩ to 2 MΩ
- Digital ambient subtraction at ADC output to suppress ambient tones
- Noise filtering with programmable bandwidth
Supports external clock and internal oscillator modes
Automatic ambient cancellation mode (AACM) to increase receiver dynamic range
Two programmable GPIO pins with flexible interrupt generation
FIFO with 128-sample depth
I²C, SPI interfaces: selectable by pin
Operating temperature range: –40°C to +85°C
2.6-mm × 2.1-mm DSBGA, 0.4-mm pitch
Supplies:
- Rx:
  - 1.7 V to 1.9 V (LDO bypass)
  - 1.9 V to 3.6 V (LDO enabled)
- Tx: 3 V to 5.5 V
- IO: 1.7 V to RX_SUP

Applications	Optical-HRM
Number of input channels	4
Resolution (Bits)	22
Number of LEDs	4
Interface type	I2C
Operating temperature range (°C)	-40 to 85
Rating	Catalog