Texas Instruments'
AFE4403 is a fully-integrated analog front-end (AFE) ideally suited for pulse oximeter applications. The device consists of a low-noise receiver channel with an integrated analog-to-digital converter (ADC), an LED transmit section, and diagnostics for sensor and LED fault detection. The device is a very configurable timing controller. This flexibility enables the user to have complete control of the device timing characteristics. To ease clocking requirements and provide a low-jitter clock to the AFE4403, an oscillator is also integrated that functions from an external crystal. The device communicates to an external microcontroller or host processor using an SPI™ interface.
The device is a complete AFE solution packaged in a single, compact DSBGA-36 (3.07 × 3.07 × 0.5 mm) and is specified over the operating temperature range of –20°C to 70°C.
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- Transmit:
- Integrated dual LED driver (H-bridge or common anode)
- Option for a third LED support for optimized SPO2, HRM, or multi-wavelength HRM
- Up to 110 dB dynamic range
- LED current: programmable to 100 mA with 8-bit current resolution
- 30 µA + average LED current
- Programmable LED on-time
- Independent LED2 and LED1 current reference
- Flexible clocking by external clock or crystal:
- Pulse frequency: 62.5 SPS to 2000 SPS
- Flexible pulse sequencing and timing control
- Input clock range: 4 MHz (min) to 60 MHz (max)
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- Receive channel with high dynamic range:
- 22-bit output in twos complement format
- Up to 105 dB dynamic range
- Low power: < 650 µA
- Dynamic power-down mode to reduce current to 300 µA
- Adaptable to a very wide range of signal amplitudes: total programmable gain: 10 kΩ to 4 MΩ
- Integrated digital ambient estimation and subtraction
- Integrated fault diagnostics: photodiode and LED open and short detection
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