Technologies for High Performance Portable Healthcare Devices Contents MEMS Inertial Sensors............................................... 3 MEMS Microphones................................................... 4 Photocurrent-to-Voltage Amplifiers............................ 5 Impedance Converter System................................... 6 Capacitive-to-Digital Controllers................................. 7 Low Power, High Performance Analog Interface......................................................... 8 Amplifiers.............................................................. 8 Data Converters..................................................... 9 Traditional high performance vital sign monitoring devices and blood analysis instruments currently found in hospitals and clinical laboratories are being redesigned for point-of-care (POC) home use. This market trend is driven by the need to lower the overall cost of healthcare while improving patient diagnosis, care, and comfort. High performance point-of-care healthcare devices must be designed to address a number of the same requirements as their hospital or clinical counterparts, such as safety from electrical shock, fail-safe features for reliable operation, and user-friendly human interfaces. These devices have additional requirements that impact design, including low power consumption, smaller form factors, measurement sensitivities due to environmental conditions, industry-standard wired or wireless communication, and lower overall system cost. Voltage References.............................................. 10 Small, Highly Accurate Temperature Sensing.............................................. 10 Analog Microcontrollers and Digital Signal Processors......................................... 11 Wireless Transfer of Data......................................... 12 iCoupler Digital Isolator Technology......................... 13 Power Management................................................. 14 www.analog.com/healthcare Portable Home Healthcare Device Functional Block Diagram LCD DISPLAY CAPACITIVE SENSORS CAPACITIVE TO DIGITAL RESISTIVE TO DIGITAL LCD BACKLIGHTING ANALOG INTERFACE (RECEIVE AND TRANSMIT) USB D+ SENSORS ACCELEROMETERS (ANALOG OUTPUT) ISOLATION USB D− ADC AMP USB 5V PHOTODIODES ELECTRODES PRECISION REFERENCE LED ARRAYS DAC PROCESSOR WIRELESS COMMUNICATION AMP IMPEDENCE TO DIGITAL ACCELEROMETERS (DIGITAL OUTPUT) MEMS MICROPHONE POWER MANAGEMENT TEMPERATURE SENSING Analog Devices offers the following technologies to meet the requirements and challenges of high performance portable home healthcare devices, including vital sign monitors, such as heart rate monitors, eldercare activity monitors, and pedometers; blood analysis/glucose meters; hearing aids; and drug/insulin delivery systems. • MEMS inertial sensors for motion detection and measurement • Photocurrent-to-voltage precision amplifiers for photodetection measurement • High precision impedance-to-digital system for blood coagulation and fluid analysis • Capacitive sensing for hermetically sealed user interfaces and body worn sensor contact • Low power, high performance components that interface to electrodes, optical sensors, and inertial sensors • Low cost, high performance microcontrollers and digital signal processors • ISM band radio system on a chip (SoC) and transceivers for reliable wireless transfer of data • iCoupler® isolation technology for safety from hazardous line voltages • High efficiency power management for battery operated devices • Small, highly accurate temperature sensors | Technologies for High Performance Portable Healthcare Devices 2 MEMS Inertial Sensors for Motion Detection and Precise Measurement MEMS inertial sensors can be used in a diverse variety of portable home healthcare and wellness applications. Eldercare activity monitors, fall detection monitors for workers at high risk, and pedometers for exercise enthusiasts rely on low-g accelerometers for motion detection, velocity, and positional measurements. Less obvious applications include device operation functions such as automatic wake-up that is triggered with a quick shake or tap of the device. ADI offers the industry’s broadest MEMS-based accelerometer portfolio available in 1-, 2-, and 3-axis configurations, with either analog or digital outputs, in low-g sensing ranges. The low power digital output devices are highly programmable to support a number of applications. Pedometers Full-featured pedometers rely on MEMS inertial sensors and software algorithms to reliably detect true steps under many use cases. For example, a user may be walking or running up and down a rough terrain or set of stairs. ADI’s MEMS inertial sensors permit more accurate detection of steps and fewer false positives combined with distance, speed, and calories burned. By taking advantage of the low cost, low power, and space requirements of ADI’s low-g accelerometers, pedometers are being integrated into an increasing number of portable consumer electronic devices—such as MP3 players, mobile phones, and athletic shoes. Human Fall Detection A fall detector based on a 3-axis iMEMS® accelerometer detects changes in motion and body position of an individual wearing a sensor by tracking acceleration changes in three orthogonal directions. The data is continuously analyzed algorithmically to determine whether the individual’s body is falling or not. If an individual falls, the device can employ GPS and a wireless transmitter to determine their location and issue an alert in order to get assistance. The core element of fall detection is an effective, reliable detection principle and algorithm to judge the existence of an emergency fall situation. Low power consumption is critical for the algorithms and the sensor because the device must be on or “active” at all times. 1024 2 1: WEIGHTLESSNESS 2: IMPACT 3: MOTIONLESS 4: INITIAL STATUS 768 512 VALUE (256/g) Statistics show that the majority of serious consequences from an unobserved fall are not the direct result of falling but rather are due to a delay in assistance and treatment. Post-fall consequences can be greatly reduced if relief personnel can be alerted in time. This is especially the case for the elderly population, however, there are many other conditions and activities for which an immediate alert to a possible fall, especially from substantial height, would be quite helpful—for example, mountaineers, construction workers, window washers, painters, and roofers. 4 VECTOR SUM X-AXIS Y-AXIS Z-AXIS 1 3 256 0 –256 –512 1 51 101 SAMPLES (50/sec) 151 201 Acceleration change curves during the process of falling. Advanced Features: Automatic Wake-Up and Power-Down Modes ADI MEMS-based digital output accelerometers offer advanced functions for system power savings and quality user experience. The accelerometer can be programmed to automatically wake up the system controller of a device when applying a short rapid shake or two when the device needs to be activated. The host controller can be configured in shutdown mode while waiting for an interrupt from the accelerometer indicating the device has been shaken. Also, the accelerometer can be programmed to shut down the system controller based on a defined and configurable time of no activity (lack of motion or movement). iMEMS Accelerometers Part Number Number of Axes g Range Sensitivity/g ±3 300 mV Sensitivity Output BW Accuracy (%) Type (kHz) Noise Voltage Density Supply (V) (𝛍g√Hz) 300 1.8 to 3.6 Supply Current (𝛍A) 350 Temp Range (°C) –40 to +85 Package ADXL335 3 ±10 Analog 1.6 ADXL345 3 ±2/±4/±8/±16 Up to 256 LSB ±10 Digital 1.6 220 2.0 to 3.6 40 to 145 –40 to +85 LFCSP LGA ADXL346 3 ±2/±4/±8/±16 Up to 256 LSB ±10 Digital 1.6 220 1.7 to 2.75 40 to 145 –40 to +85 LGA www.analog.com/healthcare | 3 High Quality Audio Acquisition Using MEMS Microphones High performance, low power MEMS microphone technology is ideal for a variety of portable home healthcare applications, including medical alert bracelets, blood pressure monitoring devices, and hearing aids—any device requiring high acoustic performance in a small form factor. ADI MEMS microphones integrate a MEMS sensor and an ASIC, allowing for an increased level of integration in the signal chain. ADI's MEMS microphone portfolio includes traditional analog output as well as various digital output formats such as the increasingly popular pulse density modulation (PDM) output and the ubiquitous I2S output. MEMS technology offers greater reliability and design flexibility over traditional electret condenser microphone (ECM) technology. There is no performance degradation over time and less sensitivity to mechanical noise. Stability across temperature and after solder reflow enables the designer to place the microphone or multiple microphones virtually anywhere in a design. MEMS microphones enable functions not previously considered for audio capture due to size and/or performance. Lower power consumption supports an extended battery life. ADMP441: Low Power, Digital Output, Omnidirectional Microphone with Bottom Port The ADMP441 high performance MEMS microphone integrates a MEMS sensor, signal conditioning, an analog-to-digital converter (ADC), antialiasing filters, power management, and an industry-standard 24-bit I2S interface. This level of integration allows the audio output from the device to feed directly into any DSP or microcontroller with an I2S port. The ADMP441 offers a flat wideband frequency response resulting in a highly intelligible, natural sound. A built-in particle filter provides high reliability. The ADMP441 has a high SNR and a high sensitivity, making it an excellent choice for far field applications. ADMP441 Features • Digital I2S interface with high precision 24-bit data ADMP441 • High SNR: 61 dBA ADC FILTER • High sensitivity: –26 dBFS SCK I2S SERIAL PORT • Flat frequency response: 100 Hz to 15 kHz POWER MANAGEMENT • Low current consumption: <1.5 mA HARDWARE CONTROL SD WSI L/R CHIPEN GND GND VDD • Package: 4.72 mm × 3.76 mm × 1.00 mm surface-mount GND • High PSRR: 80 dBFS High Performance MEMS Microphones Part Number Output Type ADMP401 Analog 62 32 100 Hz to 15 KHz –42 dBV LGA 4.72 × 3.76 × 1 ADMP404 Analog 62 32 100 Hz to 15 KHz –38 dBV LGA 3.35 × 2.5 × 0.88 ADMP405 Analog 62 32 200 Hz to 15 KHz –38 dBV LGA 3.35 × 2.5 × 0.88 ADMP421 Digital (PDM) 61 33 100 Hz to 15 KHz –26 dBFS LGA 3×4×1 ADMP441 Digital (I S) 61 33 100 Hz to 15 KHz –26 dBFS LGA 4.72 × 3.76 × 1 2 Signal-to-Noise Min Equivalent Input Ratio, SNR (dB) Noise, EIN (dB) | Technologies for High Performance Portable Healthcare Devices 4 Frequency Response Range Sensitivity @ Package 1 kHz Type Package Size (mm) Photocurrent-to-Voltage Amplifiers for Photodetection Measurement Photodetectors are commonly used in point-of-care healthcare devices, including pulse oximeters (SPO2) to measure heart rate and blood oxygen level, blood glucose test meters, flow cytometers to measure microscopic particles, and body fluid analyzers. An LED or multiple LEDs of selected wavelengths are generally pulsed through the object (for example, body tissue or fluid) while the photodetector measures the resultant transmissive or reflective signal that is proportional to the desired measurement. In all cases, the photocurrent from the photodetector is very small. Nanoamp magnitudes are not uncommon. A transimpedance amplifier (TIA) with a large value feedback resistor is most often used to convert the photocurrent to a voltage. Since the photocurrent is very small, it can get buried in noise, and careful attention must be given to system noise sources and operational amplifier selection. When selecting an op amp for measuring a very small photocurrent in a TIA configuration, choose: • Very low input bias current to prevent the op amp from bleeding off the photodetector current signal C • Low voltage and current noise to prevent adding additional noise Rf PHOTODIODE • Low offset voltage to prevent dark current from being generated in the photodetector ADC BAND-PASS FILTER The op amp voltage supplies will depend on how much dynamic range is required. TRANSIMPEDANCE AMPLIFIER ADC DRIVER Typical LED + photodetector system. Operational Amplifiers for Photocurrent Detection Measurement Voltage Noise (nV/√Hz) @ 1 kHz Current Noise (fA/√Hz) @ 1 kHz Offset Voltage (Vos /mV) AD8505 45 15 0.5 1 95 kHz AD8506 45 15 0.5 1 95 kHz AD8508 45 15 0.5 1 95 kHz ADA4691 16 N/A 0.5 0.5 3.6 MHz ADA4528 5.6 0.7 0.3 μV 220 4 MHz AD8657 60 0.1 0.35 1 200 kHz AD8641 29 0.5 0.05 1 3.5 MHz AD8625 17 0.4 0.05 1 5 MHz AD8626 17 0.4 0.05 1 5 MHz AD8627 17 0.4 0.05 1 5 MHz AD8665 10 N/A 0.7 1 4 MHz AD8666 10 N/A 0.7 1 4 MHz AD8668 10 N/A 0.7 1 4 MHz AD8605 AD8606 AD8608 8 8 8 0.01 0.01 0.01 0.08 0.08 0.08 1 1 1 10 MHz 10 MHz 10 MHz ADA4505-1 65 20 0.5 0.5 50 kHz ADA4505-2 65 20 0.5 0.5 50 kHz ADA4505-4 65 20 0.5 0.5 50 kHz Amplifier Input Bias GBWP Current (pA) Supply Voltage (V) Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Single: 2.7 to 5 Dual:±1.35 to ±2.5 Single: 2.2 to 5 Dual: ±1.10 to ±2.75 Single: 2.7 to 18.0 Dual: ±1.35 to ±9.0 Single: 5 to 26 Dual: ±2.5 to ±13 Single: 5 to 26 Dual: ±2.5 to ±13 Single: 5 to 26 Dual: ±2.5 to ±13 Single: 5 to 26 Dual: ±2.5 to ±13 Single: 5 to 16 Dual:±2.5 to ±8 Single: 5 to 16 Dual:±2.5 to ±8 Single: 5 to 16 Dual:±2.5 to ±8 Single: 2.7 to 5.5 Single: 2.7 to 5.5 Single: 2.7 to 5.5 Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Single: 1.8 to 5 Dual: ±0.9 to ±2.5 Supply Current (Per Channel) Package 16.5 μA WLCSP 16.5 μA MSOP, WLCSP 16.5 μA TSSOP, WLCSP 180 μA LFCSP, WCCSP 1.4 mA MSOP 18 μA MSOP, LFCSP 195 μA MSOP, SOIC, LFCSP 630 μA SOIC, TSSOP 630 μA SOIC, MSOP 630 μA SOIC, SC70 1.1 mA SOT-23, SOIC 1.1 mA SOIC, MSOP 1.1 mA TSSOP, SOIC 1.0 mA 1.0 mA 1.0 mA SOT-23, WLCSP MSOP, WLCSP SOIC, TSSOP 10.0 μA WLCSP, SOT-23 10.0 μA WLCSP, MSOP 10.0 μA WLCSP, TSSOP www.analog.com/healthcare | 5 High Precision Impedance-to-Digital Converter for Blood Coagulation and Fluid Analysis Blood coagulation is a complex, dynamic physiological process by which clots are formed to end bleeding at an injured site. Blood coagulation in the body is modulated by a number of cellular and other active components. The coagulation cascade describes the components of blood and how they are involved in the process of clot formation. As the cascade becomes activated, the blood progresses from a nonclotting to a clotting state, causing changes in both molecular charge states and effective charge mobility. By monitoring the global impedance of a clotting blood sample, the changes in conductivity associated with clot formation are measured. Fully Integrated, Single-Chip Impedance Converter Analyzer The AD5933 is a high precision impedance converter analyzer that combines an on-board frequency generator with a 12-bit, 1 MSPS, analog-to-digital converter (ADC). The frequency generator provides an excitation voltage to an external complex impedance at a known frequency. The response signal (current) is sampled by the on-board ADC, and a discrete Fourier transform (DFT) is processed by an on-board DSP engine. The DFT algorithm returns real (R) and imaginary (I) data words at each output frequency. The magnitude and relative phase of the impedance at each frequency point along the sweep can be easily calculated. MCLK AVDD DVDD SCL I2C INTERFACE DAC ROUT TEMPERATURE SENSOR VOUT Z(𝛚) AD5933 REAL IMAGINARY REGISTER REGISTER RFB 1024-POINT DFT VIN ADC (12 BITS) CHANGE IN RESONANCE DUE TO APPROACHING OBJECT V (Volts) DDS CORE (27 BITS) OSCILLATOR SDA RESONANT FREQUENCY LPF fo f (Hz) Special plot created by sweeping sample with different frequencies. GAIN VDD/2 AGND DGND The AD5933 block diagram illustrates the advanced level of integration contained in its single-chip form factor. Impedance-to-Digital Converters AD5933 16.776 12-bit (1 MSPS) Tuning Word Width 27 bits AD5934 16.776 12-bit (250 kSPS) 27 bits Part Master fclk Number (MHz) Resolution Impedance Internal I Supply I/O Interface Measurement Temperature Total Max Nominal Supply (V) Package Range Sensor (∙C) (mA) Serial 15 Single (+5) 16-lead SSOP 1 kΩ to MΩ ±2 Serial 1 Single (+2.7), Single (+5) 16-lead SSOP 1 kΩ to MΩ — | Technologies for High Performance Portable Healthcare Devices 6 Capacitive Sensing for Hermetically Sealed User Interfaces and Body Worn Sensor Contact The human interface must also support a wide range of individuals with varied intellectual and physical capacities including eyesight, manual dexterity, and hearing. The interface also must offer smart, closed-loop, fail-safe features that will ensure proper, reliable, and safe device operation under all conditions. Capacitive sensing is an ideal solution for developing a complete hermetically sealed device that is secure against the entry of water vapor and foreign bodies in order to maintain proper function levels and reliability under all conditions. Furthermore, a sealed capacitive sensing human interface eliminates the traditional mechanical buttons that are prone to collecting bacteria or subject to harsh cleaning liquids. Additional benefits of replacing traditional mechanical buttons with capacitive sensing include eliminating the mechanical buttons from the bill of materials and easier product assembly during product manufacturing. It is often beneficial to have information about the quality of contact between the device’s surface area and the skin before the device is activated or a measurement is taken. The range of devices could include a medical probe that needs to rest flush on the skin, a biopotential electrode sensor, or the housing holding a catheter tube in place. To achieve this additional performance, several capacitive sensor electrodes, shown in green, could be embedded directly into the device’s plastic housing at the injection molding stage during manufacturing. Once the electrode information is available, a simple algorithm running on the host controller can be applied to determine if all sensor electrodes are making proper contact with the skin. Selecting a Capacitive Sensor Controller Selecting a capacitive sensor controller should start by selecting a controller that: • Does not require external RC sensor tuning components. ACSHIELD VCC 8 GND BIAS 10 9 11 POWER-ON RESET LOGIC CIN0 19 • Includes an analog front end (AFE) that supports accurate measurements to detect the small energy on the capacitive sensors. CIN1 20 CIN2 21 • Offers on-chip environmental tracking and calibration to correct for environmental baseline drift errors. CIN3 22 • Includes on-chip parasitic capacitance offset adjustment and low latency periods from touch to response. CIN5 24 EXCITATION SOURCE CIN4 23 SWITCH MATRIX CIN6 1 CIN7 2 SENSOR OR PROBE HEAD CALIBRATION RAM AD7147/AD7147A CIN8 3 16-BIT 𝚺-𝚫 CDC CIN9 4 CALIBRATION ENGINE CIN10 5 CIN11 6 CONTROL AND DATA REGISTERS CIN12 7 VDRIVE 12 INTERRUPT AND GPIO LOGIC SERIAL INTERFACE AND CONTROL LOGIC 13 14 15 16 18 GPIO 17 SDO/ SDI/ SCLK CS/ SDA ADD0 ADD1 INT BODY WORN SENSOR Capacitive-to-Digital Controllers (CDCs) Part Resolution Number of Rate (ms) Number (Bits) Channels AD7148 16 9 8 AD7147A 16 9 13 AD7147 16 9 13 AD7156 12 10 2 Supply Voltage (V) Multi (+3.3 analog, +3.3 digital) Single (+3), Single (+3.3) Single (+3), Single (+3.3) 1.8 to 3.6 Power Dissipation 3.3 mW = full power 71 μW = low power 3.3 mW = full power 71 μW = low power 3.3 mW = full power 71 μW = low power 0.25 mW = full power 0.7 μW = shut down (3.6 V supplies) Input Base C (pF Max) CIN Range (pF) Package 20 ±8 LFCSP 20 ±8 LFCSP 20 ±8 WLCSP 12.5 0.0 to 4.0 LFCSP www.analog.com/healthcare | 7 Low Power, High Performance Analog Interface For designs that interface to electrodes, photodiodes, or analog output sensors, Analog Devices offers the industry’s broadest portfolio of low power, high performance operational amplifiers (op amps), analog-to-digital converters (ADCs), and digital-to-analog converters (DACs.) For designs requiring a higher level of integration, ADI offers a variety of application-specific standard products (ASSPs) and ASIC solutions. Contact your ADI sales representative for more information. Low Power, Precision Amplifiers High performance amplifiers provide the critical analog interface between the device and external sensors (electrodes, photodiodes, chemical assays, etc.). In portable battery-powered applications, these amplifiers must support a lower power budget and small footprint without sacrificing the performance found in higher power, clinical-level devices. The types of amplifiers and specifications required vary depending on the sensor used and the end device. Below are a few guidelines: • ECG and EEG applications including heart rate monitors: instrumentation amplifiers with a high common-mode rejection ratio; high performance operational amplifiers for the gain and filter stages employed in the device. • Photodiode applications including glucose meters (amperometric and photometric): traditional operational amplifiers as buffers; low noise, low input bias current, and low offset voltage amplifiers. • Blood pressure applications: low power, high precision instrumentation amplifiers for the bridge sensor application. Instrumentation Amplifiers Part Number Description Supply AD8220 AD8223 AD8226 AD8235 AD8236 AD627 R-R JFET Single supply R-R Wide supply R-R Small, low power Ultralow power, RRIO Micropower Single/dual Single/dual Single/dual Single Single Single/dual Gain Bandwidth Min CMRR Min CMRR @ VNOISE RTI Gain Gain Setting G = 10 Typ 1 Hz to @ 60 Hz Min 60 Hz Max Min Max Method (kHz) Gain (dB) Gain (dB) 10 Hz (𝛍V p-p) 4.6 to 36 750 μA Resistor 800 1 1000 78 94 0.8 3 to 25 0.6 mA Pin 200 5 1000 70 105 2 2.2 to 36 350 μA Resistor 160 1 1000 80 105 2 1.8 to 5.5 40 μA Resistor 8.8 5 200 60 60 5 1.8 to 5.5 40 μA Resistor 8.8 5 200 60 60 5 2.2 to 36 0.06 mA Resistor 30 5 1000 77 77 1.2 Vcc to VEE (V) Supply Current Operational Amplifiers Part Number AD8500 AD8502 AD8504 ADA4505-1 ADA4505-2 ADA4505-4 AD8505 AD8506 AD8508 AD8603 AD8607 AD8609 AD8613 AD8617 AD8619 AD8541 AD8542 AD8544 AD8538 AD8539 ADA4092-4 AD8641 AD8642 AD8643 Supply Number Voltage Process of Min/ Amps Max (V) CMOS 1 1.8/5.5 2 CMOS 1.8/5.5 4 1 CMOS 2 1.8/5.5 4 1 CMOS 2 1.8/5.5 4 1 CMOS 2 1.8/6 4 1 CMOS 2 1.8/5.5 4 1 CMOS 2 2.7/6 4 2 CMOS 2.7/5.5 4 ±1.35/ Bipolar 4 ±18 1 ±2.5/ JFET 2 ±13 4 IS/ BW @ Slew VOS Amp Rail- ACL Rate Max Max to-Rail Min (V/𝛍s) (mV) (MHz) (mA) 0.001 RRIO 0.007 0.004 1 TcVOS IB CMRR PSRR AVO Noise Typ Min Min Min @ 1 kHz Max (𝛍V/ (dB) (dB) (dB) (nV/√Hz) (pA) ºC) 3 75 90 98 190 10 Package SC70 SOT-23 TSSOP WLCSP/SOT-23 WLCSP/MSOP WLCSP/TSSOP WLCSP/SOT-23 WLCSP/MSOP WLCSP/TSSOP SOT-23 MSOP/SOIC SOIC/TSSOP SC70/SOT-23 MSOP/SOIC SOIC/TSSOP SC70/SOT-23/SOIC MSOP/SOIC/TSSOP SOIC/TSSOP SOT-23/SOIC MSOP/SOIC 0.001 RRIO 0.007 0.004 3 5 67 85 98 190 10 0.010 RRIO 0.050 0.006 3 2 90 100 105 65 2 0.020 RRIO 0.095 0.013 2.5 2 90 100 105 45 10 0.040 RRIO 0.4 0.1 0.3 1 85 80 112 25 1 0.040 RRIO 0.4 0.1 2.2 1 68 67 107 25 1 0.045 RRIO 1 0.92 6 4 40 65 86 40 60 0.180 RRIO 0.43 0.35 0.013 0.03 115 105 115 50 25 0.250 RRIO 1.4 0.4 1.5 2.5 90 98 116 30 60 TSSOP 0.290 3.5 3 0.75 2.5 90 90 106 27.5 1 SC70/SOIC MSOP/SOIC SOIC/LFCSP SS | Technologies for High Performance Portable Healthcare Devices 8 Low Power, High Performance Analog Interface (Continued) In addition to some of the amplifiers listed in the table, designers can select op amps by parameters, find expert system-level advice on design problems with our amplifier reference circuits (Circuits from the Lab™), and download design tools, selection guides, calculators, and SPICE models at www.analog.com/amplifiers. Data Converters As the world’s leading provider of data converters, Analog Devices offers digital-to-analog and analog-to-digital converters from 8 bits to 24 bits. ADI converters are unmatched in their ability to deliver performance and value, and they are supported by design tools and technical documentation engineers need to accelerate time to market. Whether the data conversion challenge is high speed or precision, engineers will find an ADC or DAC to suit every specification: accuracy, resolution, sample rate, bandwidth, power, size, and value. Low Voltage Precision Digital-to-Analog Converters (DACs) Part Number Channels Bits AD5320 1 12 AD5621 1 12 AD5622 1 12 AD5620 AD5640 AD5660 AD5322 AD5623R AD5627R AD5643R AD5663R AD5324 AD5624R AD5625R AD5644R AD5664R 1 1 1 2 2 2 2 2 4 4 4 4 4 Interface SPI SPI I 2C 1.25/2.5 1.25/2.5 1.25/2.5 No 1.25/2.5 1.25/2.5 1.25/2.5 1.25/2.5 No 1.25/2.5 1.25/2.5 1.25/2.5 1.25/2.5 SPI SPI SPI SPI SPI I2C SPI SPI SPI SPI I2C SPI SPI 12 14 16 12 12 12 14 16 12 12 12 14 16 Analog-to-Digital Converters (ADCs) Part Resolution INL THD Channels Number (Bits) (Typ) (dB) ±0.5 –82 @ AD7298 12 8 50 kHz LSB ±0.75 –80 @ AD7476A 12 1 LSB 100 kHz ±0.6 –80 @ AD7476 12 1 LSB 100 kHz On-Chip Reference (V) No No No Throughput 1 MSPS 1 MSPS 1 MSPS Supply (V) Analog: 2.8 to 3.6 Digital: 1.65 to 3.6 Analog: 2.35 to 5.25 Digital: 2.35 to 5.25 Analog: 2.35 to 5.25 Digital: 2.35 to 5.25 Package SOT-23, MSOP SC70 SC70 SOT-23, MSOP SOT-23, MSOP SOT-23, MSOP MSOP LFCSP, MSOP LFCSP, MSOP MSOP LFCSP, MSOP LFCSP, MSOP LFCSP, MSOP LFCSP, TSSOP LFCSP, MSOP LFCSP, MSOP Power Dissipation 17.4 mW 3.6 mW Package LFCSP (QFN) sc70, MSOP 3.6 mW sot-23 AD7942 14 1 ±0.4 LSB –100 @ 20 kHz 250 kSPS Analog: 2.3 to 5.5 Digital: 1.8 to 5.0 1.25 mW @ 2.5 V/100 kSPS 3.6 mW @ 5 V/100 kSPS 1.25 μW @ 2.5 V/100 SPS MSOP, QFN (LFCSP) AD7171 16 1 ±0.4 LSB n/a 125 Hz 2.7 to 5.25 0.33 mW LFCSP AD7980 16 1 ±0.6 LSB –110 @ 10 kHz 1 MSPS Analog: 2.5 to 5.0 Digital: 1.8 to 5.0 7.0 mW @ 1 MSPS 70 μW @ 10 kSPS MSOP, QFN (LFCSP) AD7685 16 1 ±0.6 LSB –110 @ 20 kHz 250 kSPS Analog: 2.3 to 5.5 Digital: 1.8 to 5.0 AD7682/ AD7689 16 4/8 ±0.4 LSB –100 @ 20 kHz 250 kSPS Analog: 2.3 to 5.5 Digital: 1.8 to 5.5 AD7986 18 1 ±0.6 LSB –115 @ 2 MSPS (TURBO = high), 20 kHz 1.5 MSPS (TURBO = low) AD7767 24 1 ±3 ppm –115 @ 1 kHz 32 kSPS 64 kSPS 128 kSPS Analog: 2.3 to 2.6 Digital: 1.8 to 2.7 Analog: 2.3 to 2.6 Digital: 1.8 to 3.6 1.4 μW @ 2.5 V/100 SPS MSOP, QFN 1.35 mW @ 2.5 V/100 kSPS (LFCSP) 4 mW @ 5 V/100 kSPS 3.5 mW @ 2.5 V/200 kSPS LFCSP 12.5 mW @ 5 V/250 kSPS 15 mW @ 2 MSPS, with external reference QFN 26 mW @ 2 MSPS, (LFCSP) with internal reference 8.5 mW @ 32 kSPS (AD7767-2) 10.5 mW @ 64 kSPS (AD7767-1) TSSOP 15 mW @ 128 kSPS (AD7767) www.analog.com/healthcare | 9 Low Power, High Performance Analog Interface (Continued) Data Conversion Knowledge Resource Analog Devices’ Data Conversion Knowledge Resource is an easy-to-navigate library of in-depth technical material focusing on key aspects of conversion stage design. Clicking on the individual blocks within the Data Conversion Knowledge Resource home page diagram serves up design and applications engineering content relevant to that specific subject. Put ADI’s 45 year span of pioneering work in data conversion to work for you. Visit the Data Conversion Knowledge Resource for design-relevant handbooks, applications notes, tutorials, webcasts, tools, and more at www.analog.com/theKnowledgeResource. Voltage References ADI’s precision micropower voltage reference products provide class-leading specification in an affordable budget. These parts feature ≤±0.1% initial accuracy, low operating current, and low output noise in small packages, ideal for battery-operated portable devices. Precision Voltage References ADR3425 2.5 Initial Accuracy (%) 0.1 100 μA max Tempco (ppm/∙C) 8 AD1580 1.225 0.08, 0.8 50 μA to 10 mA 50, 100 5 SC70/SOT-23 ADR5043 3 0.1, 0.2 50 μA to 15 mA 75, 100 25.8 SC70/SOT-23 Part Number Output Voltage (V) Operating Current 0.1 Hz to 10 Hz Noise (𝛍V p-p) 18 Package SOT-23 Small, Highly Accurate Temperature Sensing ADI’s high performance digital temperature sensors measure temperature to an accuracy of ±0.25°C over a range of –20°C to +105°C and ±0.5°C from –40°C to +125°C. These devices offer breakthrough accuracy and a high level of integration offering designers an alternative to thermistors and the peripheral parts these devices require. There is no extra signal processing, characterization, or calibration required. The sensors offer stable and reliable temperature measurement with a typical drift specification of ±0.0072°C and repeatability of ±0.015°C Digital Temperature Sensors Temperature Resolution Part Number (°C/LSB) ADT7310 0.0078°C 25°C Temperature Error (°C) 0.5 Resolution (Bits) 16 Serial Interface SPI Temperature Range (∙C) –55 to +150 Supply Voltage Range (V) +2.7 to +5.5 Package SOIC ADT7320 0.0078°C 0.0017 16 SPI –40 to +150 +2.7 to +5.5 LFCSP ADT7410 0.0078°C 0.5 16 I2C –55 to +150 +2.7 to +5.5 SOIC ADT7420 0.0078°C 0.2 16 IC –40 to +150 +2.7 to +5.5 LFCSP 10 | Technologies for High Performance Portable Healthcare Devices 2 Low Power, Low Cost Precision Analog Microcontrollers and Digital Signal Processors Analog Devices has an extensive portfolio of digital signal processors (DSPs) and analog microcontrollers for portable home healthcare device design requirements. Precision Analog Microcontroller: ARM Cortex-M3 with ISM Band Transceiver For those portable home healthcare designs requiring a high level of integration, the ADuCRF101 system on a chip (SoC) integrates high performance converter technology, an ARM Cortex-M3 processor, on-chip memory, and the added functionality of an RF transceiver for wireless communications on a single chip. It offers low operating power (190 μA/MHz) and can power down to under 1.6 μA with a state retained, making it ideal for mains and battery operated medical devices, including infusion pumps and vital sign monitors. ADuCRF101 Features XOSC26N ADC0 ADC5 MUX 14-BIT SARADC 500kSPS TEMP SENSOR BAND GAP REFERENCE UHF TRANSCEIVER PACKET HANDLER AND WAKE UP CONTROL LFXTAL1 LFXTAL2 WAKE-UP TIMER OSC AVDD LVDD ADuCRF101 IOVDD RFIO_1N ARM CORTEX M3-BASED MCU WITH ADDITIONAL PERIPHERALS 2 × GENERAL PURPOSE TIMERS POR RFIO_1P RFO2 VREF RESET XOSC26P LOW POWER RADIO INTERRUPT CONTROLLER SERIAL WIRE SPI WATCHDOG TIMER 16K BYTES SRAM (4k × 32 BITS) I2C UART 2 KBYTES 128 KBYTES FLASH/EE (32k × 32 BITS) PWM GPIOS GPIOS ADuCRF101 functional block diagram. • High performance ISM band RF transceiver • ARM Cortex-M3 32-bit RISC MCU, 128 kB Flash/EE memory, 16 kB RAM ADC0 • Operates directly from 3.6 V battery MUX • 6-channel, 14-bit, 500 kSPS SAR ADC ADC15 • 9 mm × 9 mm, 64-lead LFCSP TEMP SENSOR Precision Analog Microcontrollers with 12-Bit ARM7TDMI MCU Analog Devices precision analog microcontrollers combine precision analog functions, such as high resolution ADCs and DACs, voltage reference, temperature sensor, and a host of other peripherals, with an industry-standard microcontroller and flash memory. The ADuC712x ARM7TDMI® family integrates 12-bit ADCs, 12-bit DACs, flash, SRAM, and a host of digital peripherals designed for medical applications. Precision Analog Microcontrollers Part MCU Speed MCU Core Number (MIPS) ADuC7021 ARM7TDMI 40 ADuC7022 ARM7TDMI 40 ADuC7024 ARM7TDMI 40 ADuC7025 ARM7TDMI 40 ADuC7026 ARM7TDMI 40 ADuC7027 ARM7TDMI 40 ADuC7028 ARM7TDMI 40 ADuC7124 ARM7TDMI 40 ADuCRF101 Cortex-M3 20 1MSPS 12-BIT ADC ADuC7124/ADuC7126 CMP0 CMP1 BAND GAP REF CMPOUT VECTORED INTERRUPT CONTROLLER VREF XCLKI OSC AND PLL RST POR DAC0 12-BIT DAC DAC1 12-BIT DAC DAC2 12-BIT DAC DAC3 ARM7TDMI-BASED MCU WITH ADDITIONAL PERIPHERALS XCLKO PSM 12-BIT DAC PLA 8k × 32 SRAM 63k × 16 FLASH/EEPROM 4 GENERALPURPOSE TIMERS SPI, 2 × I2C, 2 × UART GPIO PWM JTAG EXTERNAL MEMORY INTERFACE ADuC7124 functional block diagram. Flash (kB) 62 62 62 62 62 62 62 128 128 SRAM (kB) 8 8 8 8 8 8 8 32 16 GPIO Pins 13 13 30 30 40 40 40 40 28 Resolution (Bits) 12 12 12 12 12 12 12 12 14 ADC Speed (kSPS) 1000 1000 1000 1000 1000 1000 1000 1000 500 ADC Channels 8 10 10 12 12 16 8 16 6 Other — — PWM PWM PWM PWM — PWM PWM, radio, DMA 12-Bit DAC Outputs 2 — 2 — 4 — 4 4 — Digital Signal Processors The ADSP-BF52x and ADSP-BF592 Blackfin® processors deliver the computational power required for fast, accurate results for in-home medical systems, including wearable monitoring devices and portable diagnostic systems. In addition to providing the signal processing for real-time analysis, Blackfin processors can provide control of the user interface (LCD, button, touch screen). A range of connectivity options (network wired/wireless, USB) are available to enable the transfer of data from device to patient and doctor. www.analog.com/healthcare | 11 Reliable Wireless Communication for Transfer of Data To maximize patient comfort and mobility, wireless connectivity is becoming ubiquitous. Open standards such as Bluetooth and Zigbee provide low cost options for those applications with multiple band requirements, including the 2.4 GHz band. For near-body or body worn sensors, the sub-1 GHz ISM band offers an alternative and can provide maximum design flexibility, including the ability to trade off range against power, optimize data security, and minimize software and memory overhead. To address applications utilizing ISM bands, ADI offers standalone transceivers, as well as a fully integrated system on a chip (SoC) solution. Low Power ISM Band Transceivers The ADF7023 is a low power, high performance, highly integrated 2FSK/GFSK/OOK/MSK/GMSK transceiver designed for operation in the 862 MHz to 928 MHz and 431 MHz to 464 MHz frequency bands, which cover the worldwide license-free ISM bands at 433 MHz, 868 MHz, and 915 MHz. It is suitable for circuit applications that operate under the European ETSI EN 300-220, the North American FCC (Part 15), the Chinese short-range wireless regulatory standards, or other similar regional standards. Data rates from 1 kbps to 300 kbps are supported. ADF7023 Features • Data rates supported: 1 kbps to 300 kbps • Frequency bands • 862 MHz to 928 MHz • 1.8 V to 3.6 V power supply • 431 MHz to 464 MHz • Single-ended and differential PAs • Low IF receiver with programmable IF bandwidths: 100 kHz, 150 kHz, 200 kHz, 300 kHz ADCIN_ATB3 LNA RSSI/ LOGAMP 8-BIT ADC MUX RFIO_1P RFIO_1N FSK ASK DEMOD CDR AFC AGC PA PA RFO2 DIVIDER LOOP FILTER CHARGE PUMP 8-BIT RISC PROCESSOR DIVIDER PA RAMP PROFILE 𝚺-𝚫 MODULATOR LDO4 LDO3 LDO2 SPI 64 BYTE BBRAM GPIO 256 BYTE MCR RAM TEST DAC IRQ_GP3 CS MISO SCLK MOSI GPIO1 fDEV ADF7023 LDO1 2kB RAM 256 BYTE PACKET RAM 26MHz OSC PFD IRQ CTRL 4kB ROM MAC BIAS GAUSSIAN FILTER ANALOG TEST CREGRFx CREGVCO CREGSYNTH CREGDIGx RBIAS REFERS TO PINS 17, 18, 19, 20, 25, AND 27. TEMP SENSOR BATTERY MONITOR WAKE-UP TIMER UNIT CONTROL CLOCK DIVIDER 32kHz OSC 26MHz OSC 32kHz RCOSC XOSC32KN_ATB2 XOSC32KP_GP5_ATB1 XOSC26N XOSC26P 1GPIO ADF7023 functional block diagram. ISM Band Transceiver with Microcontroller System on a Chip (SoC) The ADuCRF101 is a fully integrated SoC solution that includes an energy efficient 431 MHz to 464 MHz and 862 MHz to 928 MHz internal UHF transceiver, low power ARM Cortex-M3 core, and Flash/EE memory. The transceiver consumes only 12.8 mA in receive mode, while maintaining a typical sensitivity of –107.5 dB at 38.4 kbps (2FSK). The transmit mode is equally efficient, with supply current as low as 9 mA, depending on the user programmed RF power level. The device operates directly from a 3.6 V battery and utilizes an autonomous packet handler to minimize system current consumption during wireless communications. RF Transceivers Part Number ADF7023 ADF7242 ADuCRF101 Frequency Range (MHz) 431 to 464, 862 to 928 2400 to 2483.5 431 to 464, 862 to 928 Max Data Rate 300 kbps Phase Noise Tx Current Rx Rx Min Pos Max Pos Output Floor for Current Sensitivity Supply Supply Power (dBc/Hz) 0 dBm (mA) (mA) (dBm) (V) (V) (dBm) GFSK/FSK/MSK, –16 to 196 13 12.8 116 1.8 3.6 GMSK, OOK +13.5 DSSS-OQPSK, –20 to 2 Mbps 145 19.6 19 — 1.8 3.6 FSK/GFSK +4.8 GFSK/FSK/MSK, 300 –16 to 196 13 12.8 116 1.8 3.6 GMSK, OOK kbps +13.5 Modulation Mode 12 | Technologies for High Performance Portable Healthcare Devices Package 32-lead LFCSP 32-lead LFCSP 64-lead LFCSP iCoupler Digital Isolator Technology for Safety from Hazardous Line Voltages Portable point-of-care medical devices are using the PC USB port to upload data and in some cases to also recharge Li-Ion batteries. Since the PC is also connected to the main ac power lines, it is not uncommon to provide some extra safety precaution by either disabling the device from being used when connected to the USB port or to include electrical isolation between the USB port and the user. ADuM4160: Full/Low Speed 5 kV rms USB Digital Isolator The ADuM4160 offers 5 kV rms isolation that is ideal as an alternative to optocouplers for medical applications (IEC 60601-1 medical safety approval). The isolation provided by the ADuM4160 will electrically isolate patients and equipment protecting them from harmful surges or spikes. The isolation also eliminates the need to disconnect during defibrillation. PERIPHERAL ADuM4160 Features VDD2 • Reinforced isolation for medical applications per IEC 60601-1 VBUS1 DD+ • 5 kV rms isolation rating (1 minute) per UL 1577 USB HOST • Class 3 contact ESD performance per ANSI/ESD STM5.1-2007 DD– GND1 3.3V VBUS2 DD+ ADuM4160 DD– PIN MICROCONTROLLER POWER SUPPLY • High common-mode transient immunity (>25 kV/μs) • Direct isolation of USB D+/D− data lines supporting USB low speed and full speed data rates ADuM6000: Isolated Power for Isolated USB Applications The ADuM4160 is designed to be integrated into a USB peripheral with an upstream facing USB port. Isolated power is needed on either side of the isolation barrier in USB applications. Each side can provide its own power. For example, a patient monitor is plugged into the wall, and a laptop is powered by its own battery. Another way to achieve power on either side of the isolation barrier is for the system to use an isolated dc-to-dc converter. Designers can use the ADuM6000 with an isolated power supply, or another source to provide power. ADuM6000 Features • isoPower® integrated, isolated dc-to-dc converter • Regulated 5 V or 3.3 V output • Up to 400 mW output power • 16-lead SOIC package with >7.6 mm creepage • High temperature operation: 105°C maximum • High common-mode transient immunity: >25 kV/μs VDD1 1 OSCILLATOR RECTIFIER REGULATOR 16 VISO GND1 2 15 GNDISO NC 3 14 NC RCIN 4 13 VSEL RCOUT 5 12 NC RCSEL 6 11 NC 10 VISO 9 GNDISO VDD1 7 GND1 8 ADuM6000 ADuM6000 functional block diagram. www.analog.com/healthcare | 13 High Efficiency Power Management for Battery Operated Devices Standard lithium coin cell batteries used in point-of-care healthcare devices provide a typical output voltage in the range of 2.0 V to 3.0 V. Some high performance portable systems are also powered by rechargeable Li-Ion batteries with a 3.0 V to 4.2 V output. The two main design challenges with battery operated systems with regards to power are the battery life and the battery output voltage. Battery life can be extended by selecting components with very low quiescent and shutdown currents and by keeping the main power consuming devices, such as the host processor, in a sleep state as much as possible. The battery output level has to comply with all the IC operating voltages in the system, generally consisting of a mixture of components developed on different processes, thus different compliance voltages. ICs used for high performance portable devices operate on a wide range of voltage rails. Even if all of the ICs can operate directly off the battery, some form of regulation, such as step-up regulator, step-down regulator, or both, will be required to maintain the highest system efficiency and longest battery life. Linear Regulators Description Vout (V) Iout Max (mA) VIN Range Vmin to Vmax CMOS, low quiescent CMOS, low quiescent CMOS, 0.8 to 5 V CMOS, ultralow noise CMOS, low dropout Dual, low noise, high PSRR 9 options: 1.2 to 3.3 7 options: 2.5 to 3.3 n/a 7 options: 1.8 to 3.3 5 options: 1.2 to 2.8 7 options: 1.2 to 2.8 150 300 500 150 300 200 2.5 to 5.5 2.3 to 5.5 2.3 to 5.5 2.2 to 5.5 1.6 to 3.6 2.5 to 5.5 Part Number ADP121 ADP122 ADP125 ADP150 ADP170 ADP220 Supply Current (𝛍A) 40 45 45 10 260 220 VDROPOUT @ Rated Iout (mV) Package 90 to 120 85 130 105 66 150 WLCSP, TSOT LFCSP LFCSP WLCSP, TSOT TSOT WLCSP Switching DC-to-DC Regulators Description Vin Range (V) Vout Options (V) Iout Max (A) ADP1612 Step-up 1.8 to 5.5 VIN to 20, adjustable — 1.4 1350 650 kHz, 1.3 MHz MSOP ADP2108 Synchronous step-down 2.3 to 5.5 ADP2138 Synchronous step-down Synchronous step-down with load discharge switch Synchronous buck-boost Part Number ADP2139 ADP2504 Isw Peak Supply Current Switch (A) (𝛍A) Frequency Package 0.6 1.3 30 3 MHz WLCSP 2.3 to 5.5 1.0, 1.1, 1.2, 1.3, 1.5, 1.82, 1.8, 2.3, 2.5, 3.0, 3.3 8 options: 0.8 to 3.3 0.8 1.5 30 3 MHz WLCSP 2.3 to 5.5 8 options: 0.8 to 3.3 0.8 1.5 30 3 MHz WLCSP 2.3 to 5.5 2.8, 3.3, 3.5, 4.2, 4.5, 5.0 1 1.3 50 2.5 MHz LFCSP Buck (mA) LDO (mA) Key Features Package Multioutput Regulators Number of Switching Outputs Frequency (MHz) Part Number Product Description Vin Range (V) ADP2140 Low quiescent current buck converter with 300 mA LDO regulator 2.3 to 5.5 (LDO: 1.7 to 5.5) 2 3 600 300 Auto sequence; power good LFCSP ADP5020 General-purpose PMU 2.4 to 5.5 3 3 300, 600 150 I2C, programmable outputs LFCSP 2.4 to 5.5 3 3 150, 500 150 — WLCSP 2.45 to 5.5 9 2.5 700, 900 2.5 to 5.5 3 — — ADP5022 ADP5025 ADP5030 Dual buck regulator with 150 mA LDO System PMU for digital still cameras Dual LDO (VOUT = 1.2 V, 2.8 V) with load switch 14 | Technologies for High Performance Portable Healthcare Devices I2C, RTC, back-batt WLCSP charger 200, Load switch and WLCSP 200 level shifters 50 High Efficiency Power Management for Battery Operated Devices (Continued) Display Backlight Controllers ADI backlight drivers (controllers) are appropriate for display backlighting, keypad control, and status indicators. They extend battery life by reducing processor interaction and ambient light sensing (ALS) complexity. These intelligent state-machine products improve battery life by reducing processor interaction and improve time to market by reducing software complexities. User interface is also enhanced by the on-chip built-in controllers for automatic light adjustment based on ambient conditions. Backlight Controllers Part Number Description LED LED I 2C Topology Application Support Number Configuration ADP5501 WLED driver with ALS, RGB ADP5520 WLED driver with ALS, RGB, KBRD ADP8860 WLED driver with ALS ADP8861 WLED driver ADP8863 Fun lighting LED driver ADP8870 WLED driver with ALS and CABC 6 6 7 7 7 7 Serial Serial Parallel Parallel Parallel Parallel Inductive Inductive Capacitive Capacitive Capacitive Capacitive Backlighting Backlighting Backlighting Backlighting Backlighting Backlighting Yes Yes Yes Yes Yes Yes Max Peak Switching Brightness Iout Efficiency Frequency Control (mA) (%) (MHz) — 1 30 I2C — 1 30 I2C 89 1 60 I2C 60 PWM 89 1.32 89 1.32 60 I2C 89 1.2 60 I2C For More Information Visit Our Healthcare Website Additional healthcare device design resources and tools, including signal chains, recommended products, application notes, webcasts, technical articles, and more, are available at www.analog.com/healthcare. Subscribe to Our Healthcare eNewsletter The “Stay Tuned” healthcare eNewsletter, intended for the healthcare design engineer, will keep you informed of the latest products and tools available from ADI. Subscribe today at www.analog.com/subscribe. www.analog.com/healthcare | 15 Analog Devices, Inc. Worldwide Headquarters Analog Devices, Inc. One Technology Way P.O. Box 9106 Norwood, MA 02062-9106 U.S.A. Tel: 781.329.4700 (800.262.5643, U.S.A. only) Fax: 781.461.3113 Analog Devices, Inc. Europe Headquarters Analog Devices, Inc. Wilhelm-Wagenfeld-Str. 6 80807 Munich Germany Tel: 49.89.76903.0 Fax: 49.89.76903.157 Analog Devices, Inc. Japan Headquarters Analog Devices, KK New Pier Takeshiba South Tower Building 1-16-1 Kaigan, Minato-ku, Tokyo, 105-6891 Japan Tel: 813.5402.8200 Fax: 813.5402.1064 Analog Devices, Inc. Southeast Asia Headquarters Analog Devices 22/F One Corporate Avenue 222 Hu Bin Road Shanghai, 200021 China Tel: 86.21.2320.8000 Fax: 86.21.2320.8222 i 2c refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors). ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. AH09519-0-11/11(A) www.analog.com/healthcare