AFE4490 Datasheet, PDF (1/70 Pages) Texas Instruments – Integrated Analog Front-End for Pulse Oximeters

AFE4490
www.ti.com
SBAS602B – DECEMBER 2012 – REVISED FEBRUARY 2013
Integrated Analog Front-End for Pulse Oximeters
Check for Samples: AFE4490
FEATURES
1
•23 Fully-Integrated Analog Front-End for
Pulse Oximeter Applications:
– Flexible Pulse Sequencing and
Timing Control
• Transmit:
– Integrated LED Driver
(H-Bridge or Push/Pull)
– 110-dB Dynamic Range Across Full Range
(Enables Low Noise at Low LED Current)
– LED Current:
– Programmable Ranges of 50 mA, 75 mA,
100 mA, 150 mA, and 200 mA,
Each with 8-Bit Current Resolution
– Low Power:
– 100 µA + Average LED Current
– LED On-Time Programmability from
(50 µs + Settle Time) to 4 ms
– Independent LED2 and LED1 Current
Reference
• Receive Channel with High Dynamic Range:
– Input-Referred Noise:
13 pA_RMS (0.1-Hz to 5-Hz Bandwidth)
– 13.5 Noise-Free Bits (0.1 Hz to 5 Hz)
– Analog Ambient Cancellation Scheme with
Selectable 1-µA to 10-µA Ambient Current
– Low Power: < 2.3 mA at 3.0-V Supply
– Rx Sample Time: 50 µs to 250 µs
– I-V Amplifier with Seven Separate LED2 and
LED1 Programmable Feedback R and C
Settings
– Integrated Digital Ambient Estimation and
Subtraction
• Integrated Fault Diagnostics:
– Photodiode and LED Open and
Short Detection
– Cable On/Off Detection
• Supplies:
– Rx = 2.0 V to 3.6 V
– Tx = 3.0 V or 5.25 V
• Package: Compact QFN-40 (6 mm × 6 mm)
• Specified Temperature Range: –40°C to +85°C
APPLICATIONS
• Medical Pulse Oximeter Applications
• Industrial Photometry Applications
DESCRIPTION
The AFE4490 is a fully-integrated analog front-end
(AFE) that is ideally suited for pulse-oximeter
applications. The device consists of a low-noise
receiver channel with a 22-bit analog-to-digital
converter (ADC), an LED transmit section, and
diagnostics for sensor and LED fault detection. The
AFE4490 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
AFE4490, 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 AFE4490 is a complete AFE solution packaged
in a single, compact QFN-40 package (6 mm ×
6 mm) and is specified over the operating
temperature range of –40°C to +85°C.
2.2-V Supply
Rx
CPD
+
TIA
+
Stage 2
Gain
Photodiode
Diagnostic
PD Open or Short
Cable Off
LED Open or Short
LED2
AMBLED2
LED1
AMBLED1
+
Buffer
û ADC
Timing
Controller
LED2 Data
Amb (LED2) Data
(LED2 t Amb) Data
LED1 Data
Amb (LED1) Data
(LED1 t Amb) Data
AFE
SPI
SPI Interface
LED
Driver
LED
Tx Driver
Supply
LED Current
Control
DAC
5-V Supply
OSC
8 MHz
AFE
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Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SPI is a trademark of Motorola.
2
All other trademarks are the property of their respective owners.
3
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2012–2013, Texas Instruments Incorporated