Texas Instruments AFE4490RHAR

Overview

AFE4490RHAR from Texas Instruments is a fully-integrated analog front-end IC designed for medical pulse oximeter systems, featuring dual LED drivers (LED1/LED2), two ambient-cancellation photodiode receiver channels (INP/INN), 22-bit ADC, programmable timing control, and integrated diagnostics. It delivers 110-dB dynamic range, 50 pARMS input-referred noise at 5-µA PD current, and operates from 2.0–3.6 V Rx and 3.0/5.25 V Tx supplies.

For engineers reviewing the AFE4490RHAR datasheet, AFE4490RHAR pinout, AFE4490RHAR application, or AFE4490RHAR equivalent, this device supports precise photoplethysmography (PPG) signal acquisition in wearable and clinical oximetry designs requiring ambient subtraction, fault detection, and low-noise analog signal conditioning with SPI interface control.

Technical Context

The AFE4490RHAR implements a dual-path transimpedance amplifier (TIA) architecture with independent programmable feedback R/C networks for LED1 and LED2 channels, plus selectable ambient current sources (1–10 µA) for real-time ambient cancellation. Its timing controller supports flexible pulse sequencing with LED on-times from 50 µs + settle time to 4 ms and programmable PRF up to 1200 Hz.

It integrates an 8-MHz crystal oscillator, digital ambient estimation and subtraction logic, and diagnostics for photodiode open/short, LED open/short, and cable disconnect detection. The 22-bit ADC operates with configurable sample time (50 µs–4 ms) and delivers 13.5 noise-free bits at 5-µA photodiode current.

Key Specifications

Pinout & Package

VQFN-40 (6 mm × 6 mm) package with wettable flanks, 0.5-mm pitch, and exposed thermal pad. RoHS-compliant, moisture-sensitive level 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar analog front-end applications.

Compared with AFE4400RHA and AFE4403YFFR, the AFE4490RHAR provides broader LED current range (200 mA), full –40°C to +85°C qualification, integrated 8-MHz oscillator, and comprehensive diagnostics-making it the only option qualified for clinical-grade pulse oximetry with ambient cancellation and fault resilience.

Availability

AFE4490RHAR is available at Aetrix Electronics and suitable for wearable pulse oximeters, clinical patient monitors, and portable vital sign sensors requiring stable component supply, long-term lifecycle support, and medical-grade reliability assurance.

Supply support for AFE4490RHAR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog, embedded processing, and connectivity technologies, with leadership in precision analog signal chains and medical-grade ICs.

The AFE4490RHAR belongs to TI's medical analog front-end product line, engineered specifically for photoplethysmography-based physiological sensing-prioritizing low-noise performance, ambient immunity, integrated diagnostics, and regulatory-ready design.

FAQ

What is the primary function of the AFE4490RHAR in a pulse oximeter system?

The AFE4490RHAR serves as the complete analog signal acquisition engine in pulse oximeters, performing synchronized LED driving (red and IR), ambient-cancelled photodiode current amplification, 22-bit digitization, and real-time diagnostics. Its dual-channel architecture, 110-dB dynamic range, and integrated timing controller make the AFE4490RHAR essential for extracting accurate AC/DC PPG ratios used in SpO₂ computation.

Does the AFE4490RHAR include an internal oscillator, and what is its purpose?

Yes, the AFE4490RHAR integrates an 8-MHz crystal oscillator using external XIN/XOUT pins. This oscillator provides a low-jitter clock source for the ADC, timing controller, and digital logic-eliminating the need for an external clock generator and reducing system BOM count and EMI risk. The AFE4490RHAR oscillator ensures deterministic timing for LED pulsing and ADC sampling critical to motion-robust PPG acquisition.

How does ambient light cancellation work in the AFE4490RHAR?

The AFE4490RHAR implements analog ambient cancellation by injecting a programmable 1–10 µA current into the photodiode node during ambient-only sampling phases, then digitally estimating and subtracting ambient contribution from active LED-driven samples. This dual-stage method-combining analog current injection and digital subtraction-enables robust operation under varying ambient light conditions without requiring external optical filters or mechanical shielding. The AFE4490RHAR achieves this with no additional external components.

What diagnostic capabilities does the AFE4490RHAR provide, and how are they signaled?

The AFE4490RHAR detects photodiode open/short, LED open/short, and cable disconnect conditions using internal current comparators and state-machine logic. These faults are reported via dedicated digital output pins: LED_ALM, PD_ALM, and DIAG_END. Each flag can trigger interrupts on an external MCU, enabling immediate system response-such as disabling LED drive or initiating recalibration-without polling. The AFE4490RHAR diagnostics operate autonomously during normal operation and require no host intervention.

What are the power supply requirements for the AFE4490RHAR, and why are they split?

The AFE4490RHAR requires two independent supplies: RX_ANA_SUP/RX_DIG_SUP (2.0–3.6 V) for analog and digital receiver circuitry, and LED_DRV_SUP/TX_CTRL_SUP (3.0 V or 5.25 V) for LED drivers and transmit control. This separation prevents switching noise from high-current LED pulses from coupling into the sensitive analog receive path-preserving SNR and ensuring clean PPG waveform acquisition. The AFE4490RHAR specifies < 2.3 mW total power at 3.0-V supply, including both analog and LED drive contributions.