Life Sciences & Medical Instrumentation

The AD7147 is an integrated CDC with on-chip environmental calibration. The CDC has 13 inputs channeled through a switch matrix to a 16-bit, 250 kHz sigma-delta (Σ-Δ) converter. The CDC is capable of sensing changes in the capacitance of the external sensors and uses this information to register a sensor activation. By programming the registers, the user has full control over the CDC setup.

High resolution sensors require minor software to run on the host processor.

The AD7147 is designed for single electrode capacitance sensors (grounded sensors). There is an active shield output to minimize noise pickup in the sensor.

The AD7147 has on-chip calibration logic to compensate for changes in the ambient environment. The calibration sequence is performed automatically and at continuous intervals as long as the sensors are not touched. This ensures that there are no false or non-registering touches on the external sensors due to a changing environment.

The AD7147 has an SPI-compatible serial interface, and the AD7147-1 has an I²C^®-compatible serial interface. Both parts have an interrupt output, as well as a GPIO. There is a V_DRIVE pin to set the voltage level for the serial interface independent of V_CC.

The AD7147 is available in a 24-lead, 4 mm × 4 mm LFCSP and operates from a 2.6 V to 3.6 V supply. The operating current consumption in low power mode is typically 26 μA for 13 sensors.

Applications

• Cell phones
• Personal music and multimedia players
• Smart handheld devices
• Television, A/V, and remote controls
• Gaming consoles
• Digital still cameras

The ADT7420 is a high accuracy digital temperature sensor offering breakthrough performance over a wide industrial range, housed in a 4 mm × 4 mm LFCSP package. It contains an internal band gap reference, a temperature sensor, and a 16-bit ADC to monitor and digitize the temperature to 0.0078°C resolution. The ADC resolution, by default, is set to 13 bits (0.0625°C). The ADC resolution is a user programmable mode that can be changed through the serial interface.

The ADT7420 is guaranteed to operate over supply voltages from 2.7 V to 5.5 V. Operating at 3.3 V, the average supply current is typically 210 μA. The ADT7420 has a shutdown mode that powers down the device and offers a shutdown current of typically 2.0 μA at 3.3 V. The ADT7420 is rated for operation over the −40°C to +150°C temperature range.

Pin A0 and Pin A1 are available for address selection, giving the ADT7420 four possible I²C addresses. The CT pin is an open-drain output that becomes active when the temperature exceeds a programmable critical temperature limit. The INT pin is also an open-drain output that becomes active when the temperature exceeds a programmable limit. The INT pin and CT pin can operate in comparator and interrupt event modes.

Product Highlights

1. Ease of use, no calibration or correction required by the user.
2. Low power consumption.
3. Excellent long-term stability and reliability.
4. High accuracy for industrial, instrumentation, and medical applications.
5. Packaged in a 16-lead, 4 mm × 4 mm LFCSP RoHS-compliant package.

Applications

• RTD and thermistor replacement
• Thermocouple cold junction compensation
• Medical equipment
• Industrial control and test
• Food transportation and storage
• Environmental monitoring and HVAC
• Laser diode temperature control

Many traditional operational amplifier pinouts have a supply pin that is next to the noninverting input. A guard trace must be routed between these pins to avoid leakage currents much larger than the bias current of a FET input op amp. Guard traces can be routed between pins for large packages, such as DIP or even SOIC; however, the board area consumed by these packages is prohibitive for many modern applications. The AD8244 solves this problem with a unique pinout that physically separates the high impedance inputs from the low impedance supplies and outputs of the other buffers. This configuration simplifies guarding while reducing board space, allowing high performance and high density in the same design.

The AD8244 design is focused on solving problems specific to buffers. This includes close channel-to-channel matching which allows channels of the AD8244 to be used in differential signal chains with minimal error. With its low voltage noise, wide supply range, and high precision, the AD8244 is also flexible enough to provide high performance anywhere a unity-gain buffer is needed, even with low source resistance.

The AD8244 is specified over the industrial temperature range of −40°C to +85°C. It is available in a 10-lead MSOP package.

APPLICATIONS

• Biopotential electrodes
• Medical instrumentation
• High impedance sensor conditioning
• Filters
• Photodiode amplifiers

The AD5933 and AD5934 are high precision impedance converter system solutions that combine an on-chipprogrammable frequency generator with a 12-bit, 1 MSPS (AD5933) or 250 kSPS (AD5934) analog-to-digital converter (ADC). The tunable frequency generator allows an external complex impedance to be excited with a known frequency.

The circuit shown in Figure 1 yields accurate impedance measurements extending from the low ohm range to several hundred kΩ and also optimizes the overall accuracy of the AD5933/AD5934.

The circuit shown in Figure 1 is a completely isolated low power pH sensor signal conditioner and digitizer with automatic temperature compensation for high accuracy.

The circuit gives 0.5% accurate readings for pH values from 0 to 14 with greater than 14-bits of noise-free code resolution and is suitable for a variety of industrial applications such as chemical, food processing, water, and wastewater analysis.

This circuit supports a wide variety of pH sensors that have very high internal resistance that can range from 1 MΩ to several GΩ, and digital signal and power isolation provides immunity to noise and transient voltages often encountered in harsh industrial environments.

The circuit in Figure 1 is a complete single-supply, low noise LED current source driver controlled by a 16-bit digital-to-analog converter (DAC). The system maintains ±1 LSB integral and differential nonlinearity and has a 0.1 Hz to 10 Hz noise of less than 45 nA p-p for a full-scale output current of 20 mA.

The innovative output driver amplifier eliminates the crossover nonlinearity normally associated with most rail-to-rail input op amps that can be as high as 4 LSBs or 5 LSBs for a 16-bit system.

This industry-leading solution is ideal for pulse oximetry applications where 1/f noise superimposed on the LED brightness levels affects the overall accuracy of the measurement.

Total power dissipation for the three active devices is less than 20 mW typical when operating on a single 5 V supply.

The circuit shown in Figure 1 is a dual-channel colorimeter featuring a modulated light source transmitter, programmable gain transimpedance amplifiers on each channel, and a very low noise, 24-bit Σ-Δ analog-to-digital converter (ADC). The output of the ADC connects to a standard FPGA mezzanine card. The FPGA takes the sampled data from the ADC and implements a synchronous detection algorithm.

By using modulated light and digital synchronous detection rather than a constant (dc) source, the system strongly rejects any noise sources at frequencies other than the modulation frequency, providing excellent accuracy.

The dual-channel circuit measures the ratio of light absorbed by the liquids in the sample and reference containers at three different wavelengths. This measurement forms the basis of many chemical analysis and environmental monitoring instruments used to measure concentrations and characterize materials through absorption spectroscopy.

The circuit in Figure 1 is a two-channel, bank isolated, wide bandwidth data acquisition (DAQ) system, implemented with a simultaneous sampling architecture using an analog-to-digital converter (ADC) per channel. The system achieves high channel density along with isolation between the bank and the digital backplane, all while delivering exceptional performance. The design also makes efficient use of isolation channels by configuring the ADCs in daisy-chain mode and utilizing an isolator product with a trimmed delay clock feature. Power generation is also simplified using an isolator with an integrated pulse width modulation (PWM) controller and transformer driver to perform dc-to-dc conversion across the isolation barrier. The system also includes many common features of a typical DAQ signal chain, including input circuit protection, programmable gain channels, high accuracy, and high performance.

The simultaneous sampling realizes multiple channels without sample rate limitations inherent in multiplexed DAQ signal chains. The analog front end (AFE) design is also simpler than the multiplexed option, because the settling performance requirements of the system are less demanding. Sampling occurs simultaneously for each channel, while sequential sampling systems have delays between channels.

Digital bank isolated DAQ designs provide protection for digital back end circuitry and reduce ground loop and common-mode interference between banks. They feature multiple DAQ signal chains per ground plane, and can be implemented with fewer digital isolation devices than channel-to-channel isolated systems.

The system functional diagram in Figure 1 is a precision analog front end for measurement of current down to the femtoampere range. This industry-leading solution is ideal for chemical analyzers and laboratory grade instrument where an ultrahigh sensitivity analog front end is required for signal conditioning current output sensors such as photodiodes, photomultiplier tubes, and Faraday cups. Applications that can use this solution include mass spectrometry, chromatography, and coulometry.

The EVAL-CN0407-SDPZ provides a reference design for real-world application by partitioning the system into a low-leakage mezzanine board and a data acquisition board. The input signal conditioning is implemented with the ADA4530-1 on the mezzanine board. The ADA4530-1 is an electrometer-grade amplifier with ultralow input bias current of 20 fA maximum at 85°C. A guard buffer is integrated on the chip to isolate the input pins from leakage to the printed circuit board (PCB). The default amplifier configuration is in the transimpedance mode with a 10 GΩ glass resistor and a metal shield that prevents leakage current from entering any of the high impedance paths on the board. In addition, the mezzanine board includes unpopulated resistor and capacitor pads to allow prototyping with surface-mount feedback resistors as well as other input configurations.

The data acquisition board uses an AD7172-2 24-bit Σ-Δ analog-to-digital-converter (ADC) and is powered from a single 9 V dc supply. The on-board supply generates all necessary voltages required to power both boards. The board connects to a PC via the SDP-S board (EVAL-SDP-CS1Z) and uses digital isolation to prevent noise from the USB bus or ground loops from degrading low current measurements.

The circuit shown in Figure 1 measures indoor air quality by using a metal-oxide sensor to detect gases composed of volatile organic compounds. The sensor is composed of a heating resistor and a sensing resistor. When the sense resistor is heated, its value changes as a function of the concentrations of different gases.

The circuit uses a 12-bit, current output digital-to-analog converter (DAC) for precision control of the heater current, and the flexible software allows the heater to operate in one of the following four modes: constant current, constant voltage, constant resistance, and constant temperature.

The circuit is able measure a wide range of sense resistance values by using a software-selectable, five range resistor divider. The board also includes a temperature and humidity sensor that is used for compensating the gas concentration value.

The circuit shown in Figure 1 is a portable gas detector, using a 4-electrode electrochemical sensor, for simultaneous detection of two distinct gases. The potentiostatic circuit uses an optimum combination of components designed to provide single-supply, low power, and low noise performance, while offering a high degree of programmability to accommodate a variety of sensors for different types of gases.

Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of many toxic gases. Most sensors are gas specific and have usable resolutions under one part per million (ppm) of gas concentration.

The Alphasense COH-A2 sensor, which detects carbon monoxide (CO) and hydrogen sulfide (H₂S), is used in this example.

The EVAL-CN0396-ARDZ printed circuit board (PCB) is designed in an Arduino-compatible shield form factor and interfaces to the EVAL-ADICUP360 Arduino-compatible platform board for rapid prototyping.

The circuit shown in Figure 1 is a cost effective, isolated, multi-channel data acquisition system that is compatible with standard industrial signal levels. The components are specifically selected to optimize settling time between samples, providing 18-bit performance at channel switching rates up to approximately 750 kHz.

The circuit can process eight gain-independent channels and is compatible with both single-ended and differential input signals.

The analog front end includes a multiplexer, programmable gain instrumentation amplifier (PGIA); precision analog-to-digital converter (ADC) driver for performing the single-ended to differential conversion; and an 18-bit, 2.0 MSPS precision PulSAR^® ADC for sampling the signal on the active channel. Gain configurations of 0.4, 0.8, 1.6, and 3.2 are available.

The maximum sample rate of the system is 2 MSPS in turbo mode, and 1.5 MSPS in normal mode. The channel switching logic is synchronous to the ADC conversions, and the maximum channel switching rate is 1.5 MHz. A single channel can be sampled at up to 2 MSPS with 18-bit resolution in turbo mode. Channel switching rates up to 750 kHz also provide 18-bit performance.

The circuit shown in Figure 1 provides a method to convert a high frequency single-ended input signal to a balanced differential signal used to drive the AD7626 16-bit, 10 MSPS PulSAR^® ADC. The circuit maximizes the AD7626 performance for high frequency input tones using the ADA4932-1 low power differential amplifier to drive the ADC. The true benefit of this combination of devices is high performance at low power.

The AD7626 industry breakthrough dynamic performance of 91.5 dB SNR at 10 MSPS with 16-bit INL performance, no latency, and LVDS interface, all coupled with power dissipation of only 136 mW. A key feature of the SAR architecture used in the AD7626 is the ability to sample at 10 MSPS without the latency, or "pipeline delay," typically incurred with pipeline ADCs coupled with the excellent linearity performance.

The ADA4932-1 has low distortion (100 dB SFDR @ 10 MHz), fast settling time (9 ns to 0.1%), high bandwidth (560 MHz, −3 dB, G = 1), and low current (9.6 mA). These characteristics make it the ideal choice for driving the AD7626. It also features the functionality to easily set the required output common- mode voltage.

The combination offers industry-leading dynamic performance and small board area with the AD7626 in a 5 mm × 5 mm, 32-lead LFCSP, the ADA4932-1 in a 3 mm × 3 mm, 16-lead LFCSP, and the AD8031 in a 5-lead SOT-23 package.

The circuit shown in Figure 1 is a high speed photodiode signal conditioning circuit with dark current compensation. The system converts current from a high speed silicon PIN photodiode and drives the inputs of a 20 MSPS analog-to-digital converter (ADC). This combination of parts offers spectral sensitivity from 400 nm to 1050 nm with 49 nA of photocurrent sensitivity, a dynamic range of 91 dB, and a bandwidth of 2 MHz. The signal conditioning circuitry of the system consumes only 40 mA of current from the ±5 V supplies making this configuration suitable for portable high speed, high resolution light intensity applications, such as pulse oximetry.

Other suitable applications for this circuit are as an analog opto-isolator. It can also be adapted to applications that require larger bandwidth and less resolution such as adaptive speed control systems.

This circuit note discusses the design steps needed to optimize the circuit shown in Figure 1 for a specific bandwidth including stability calculations, noise analysis, and component selection considerations.

The circuit shown in Figure 1 is a high speed FET input, gain of- 5 instrumentation amplifier (in-amp) with a wide bandwidth (35 MHz) and excellent ac common-mode rejection, CMR, (55 dB at 10 MHz). The circuit is ideal for applications where a high input impedance, fast in-amp is required, including RF, video, optical signal sensing, and high speed instrumentation. The high CMR and bandwidth also makes it ideal as a wideband differential line receiver.

Most discrete in-amps require expensive matched resistor networks to achieve high CMR; however, this circuit uses an integrated difference amplifier with on-chip matched resistors to improve performance, reduce cost, and minimize printed circuit board (PCB) layout area.

The composite in-amp circuit shown in Figure 1 has the following performance:

• Offset voltage: 4 mV maximum
• Input bias current: 2 pA typical
• Input common-mode voltage: −3.5 V to +2.2 V maximum
• Input differential voltage: ±3.5 V/G1 maximum, where G1 is the gain of the first stage
• Output voltage swing: 0.01 V to 4.75 V typical with 150 Ω load
• Bandwidth (−3 dB): 35 MHz typical for G = 5
• Common-mode rejection: 55 dB at 10 MHz typical
• Input voltage noise: 10 nV/√Hz at 100 kHz RTI typical
• Harmonic distortion: −60 dBc at 10 MHz, G = 5, V_OUT = 1 V p-p, R_L = 1 kΩ

Most fully integrated in-amps are fabricated on bipolar or complementary bipolar processes and are optimized for low frequency applications with high CMR at 50 Hz or 60 Hz. However, there is a growing need for wide bandwidth in-amps for video and RF systems to amplify high speed signals and provide common-mode rejection of unwanted high frequency signals.

When a very high speed, wide bandwidth in-amp is needed, one common approach is to use two discrete op amps with high input impedance to buffer and amplify the differential input signal in the first stage, and then configure a single amplifier as a difference amplifier in the second stage to provide a differential-to-single-ended conversion. This configuration is known generally as a 3-op-amp in-amp. This approach requires four relatively expensive precision-matched resistors for good CMR. Errors in matching produce errors at the final output.

The circuit shown in Figure 1 solves this problem by using the ADA4830-1 integrated high speed difference amplifier. The laser-trimmed thin film resistors are matched to very high precision, thereby eliminating the need for four relatively expensive precision-matched external resistors.

In addition, the use of the high speed, dual ADA4817-2 as the input stage amplifier allows the composite in-amp to provide a bandwidth as high as 80 MHz when the overall gain of the circuit is 2.5.

The use of the dual ADA4817-2 amplifiers in a single 4 mm × 4 mm LFCSP package and the integrated ADA4830-1 difference amplifier significantly reduces board space, thereby reducing design costs for large systems.

The circuit can be used in noisy environments because both the ADA4817-2 and ADA4830-1 offer low noise and excellent CMR performance at high frequencies.

The circuit shown in Figure 1 is a 16-bit, 100 kSPS successive approximation analog-to-digital converter (ADC) system that has a drive amplifier that is optimized for a low system power dissipation of 7.35 mW for input signals up to 1 kHz and sampling rates of 100 kSPS.

This approach is highly useful in portable battery powered or multichannel applications, or where power dissipation is critical. It also provides benefits in applications where the ADC is idle most of the time between conversion bursts.

Drive amplifiers for high performance successive approximation ADCs are typically selected to handle a wide range of input frequencies. However, when an application requires a lower sampling rate, considerable power can be saved because reducing the sampling rate reduces the ADC power dissipation proportionally.

To take full advantage of the power saved by reducing the ADC sampling rate, a low bandwidth, low power amplifier is required. For instance, the 80 MHz ADA4841-1 op amp (12 mW at 10 V) is recommended for operation with the AD7988-1 16-bit successive approximation register (SAR) ADC (0.7 mW at 100 kSPS). The total system power dissipation including the ADR435 reference (4.65 mW at 7.5 V) is 17.35 mW at 100 kSPS.

For input bandwidths up to 1 kHz and sampling rates of 100 kSPS, the 3 MHz AD8641 op amp (2 mW at 10 V) offers excellent signal-to-noise ratio (SNR) and total harmonic distortion (THD) performance and reduces total system power from 17.35 mW to 7.35 mW, which is a 58% power savings at 100 kSPS.

The circuit shown in Figure 1 is a 16-bit, 300 kSPS successive approximation analog-to-digital converter (ADC) system that has a drive amplifier that is optimized for a low system power dissipation of 10.75 mW for input signals up to 4 kHz and sampling rates of 300 kSPS.

This approach is highly useful in portable battery powered or multichannel applications, or where power dissipation is critical. It also provides benefits in applications where the ADC is idle most of the time between conversion bursts.

Drive amplifiers for high performance successive approximation ADCs are typically selected to handle a wide range of input frequencies. However, when an application requires a lower sampling rate, considerable power can be saved because reducing the sampling rate reduces the ADC power dissipation proportionally.

To take full advantage of the power saved by reducing the ADC sampling rate, a low bandwidth, low power amplifier is required.

For example, the 80 MHz ADA4841-1 op amp (12 mW at 10 V) is recommended for inputs up to approximately 100 kHz with the AD7988-5 16-bit successive approximation register (SAR) ADC (3.5 mW at 500 kSPS and 2.1 mW at 300 kSPS). The total system power dissipation including the ADR435 reference (4.65 mW at 7.5 V) is 18.75 mW at 300 kSPS.

For input bandwidths less than 4 kHz and sampling rates less than 300 kSPS, the 1.3 MHz OP1177 op amp (4 mW at 10 V) offers excellent signal-to-noise ratio (SNR) and total harmonic distortion (THD) performance and reduces total system power from 18.75 mW to 10.75 mW, which is a 43% power savings at 300 kSPS.

The universal serial bus (USB) is rapidly becoming the standard interface for most PC peripherals. It is displacing RS-232 and the parallel printer port because of superior speed flexibility and support of device hot swap. There has been a strong desire on the part of industrial and medical equipment manufacturers to use the bus as well, but adoption has been slow because there has not been a good way to provide the isolation required for connections to machines that control dangerous voltages or low leakage defibrillation proof connections in medical applications.

The ADuM4160 is designed primarily as an isolation element for a peripheral USB device. However, there are occasions when it is useful to create an isolated cable function. Several issues must be addressed to use the ADuM4160 for this application. Whereas the buffers on the upstream and downstream sides of the ADuM4160 are the same and capable of driving a USB cable, the downstream buffers must be capable of adjusting speed to a full or low speed peripheral that is connected to it. The upstream connection must act like a peripheral, and the downstream connection must behave like a host.

Unlike the case of building a dedicated peripheral interface where the speed is known and not changed, host applications must adapt to detect whether a low or full speed device has been connected. The ADuM4160 is intended to be hardwired to a single speed via pins; therefore, it works when the peripheral plugged into its downstream side is the correct speed, but it fails when the wrong speed peripheral is attached. The best way to address this is to combine the ADuM4160 with a hub controller.

The upstream side of a hub controller can be thought of as a standard fixed speed peripheral port that can be easily isolated with the ADuM4160, whereas the downstream ports are all handled by the hub controller. However, in many cases, while it is not certifiable as fully USB compliant, a single speed cable is acceptable from a practical standpoint, especially if custom connectors are used so that it cannot be confused with a compliant device. The hub chip can be eliminated, and the design becomes very small and simple.

The ADuM4160 provides an inexpensive and easy way to implement an isolation buffer for medical and industrial peripherals. The challenge that must be met is to use this to create a bus-powered cable isolator by pairing the ADuM4160 with a small isolated dc-to-dc converter such as the ADuM5000. As with isolating any device, the services that the ADuM4160 provides are as follows:

1. Directly isolates, in the upstream, the USB D+ and D− lines of a cable.
2. Implements an automatic scheme for data flow of control that does not require external control lines.
3. Provides medical grade isolation.
4. Supports full speed or low speed signaling rates.
5. Supports isolated power delivery through the cable.

The goal of the application circuit shown in Figure 1 is to isolate a peripheral device that already implements a USB interface. It is not possible to make a fully compliant bus-powered cable because there are no 100% efficient power converters to transfer the bus voltage across the barrier. In addition, the quiescent current of the converter does not comply with the standby current requirements of the USB standard. This is all in addition to the speed detection limitations of the ADuM4160. What can be achieved is a fixed speed or switch-controlled speed cable that can supply a modest power to the downstream peripheral. However, it is a custom application that is not completely compliant with the USB standard.

The universal serial bus (USB) is rapidly becoming the standard interface for most PC peripherals. It is displacing RS-232 and the parallel printer port because of superior speed, flexibility, and support of device hot swap. There has been a strong desire on the part of industrial and medical equipment manufacturers to use this bus as well, but adoption has been slow because there has not been a good way to provide the isolation required for connections to machines that control dangerous voltages or low leakage defibrillation proof connections in medical applications.

The ADuM4160 provides an inexpensive and easy to implement isolation buffer for medical and industrial peripherals. The challenges that need to be met are:

1. Isolate directly in the USB D+ and D− lines allowing the use of existing USB infrastructure in microprocessors.
2. Implement an automatic scheme for data flow of control that does not require external control lines.
3. Provide medical grade isolation.
4. Allow a complete peripheral to meet the USB-IF certifi-cation standards.
5. Support full speed (12 Mbps) and low speed (1.5 Mbps) signaling rates.
6. Support flexible power configurations.

The circuit shown in Figure 1 isolates a peripheral device that already supports a USB interface. Because the peripheral is not explicitly defined in this circuit, power to run the secondary side of the isolator has been provided as part of the solution. If the circuit is built onto the PCB of a peripheral design, power could be sourced from the peripheral’s off line supply, a battery, or the USB cable bus power, depending on the needs of the application.

The application circuit shown is typical of many medical and industrial applications.

The universal serial bus (USB) is rapidly becoming the standard interface for most PC peripherals. It is displacing RS-232 and the parallel printer port because of superior speed, flexibility, and support of device hot swap. There has been a strong desire on the part of industrial and medical equipment manufacturers to use the bus as well, but adoption has been slow because there has not been a good way to provide the isolation required for connections to machines that control dangerous voltages or low leakage defibrillation proof connections in medical applications.

The ADuM4160 is designed primarily as an isolation element for a peripheral USB device. However, there are occasions when it is useful to isolate a host device. Several issues must be addressed to use the ADuM4160 for this application. Whereas the buffers on the upstream and downstream sides of the ADuM4160 are the same and capable of driving a USB cable, the downstream buffers must be capable of adjusting speed to a full or low speed peripheral that is connected to it.

Unlike the case of building a dedicated peripheral interface where the speed is known and not changed, host applications must adapt. The ADuM4160 is intended to be hardwired to a single speed via pins; therefore, it works when the peripheral plugged into its downstream side is the correct speed, but it fails when the wrong speed peripheral is attached. The best way to address this is to combine the ADuM4160 with a hub controller.

The upstream side of a hub controller can be thought of as a standard fixed speed peripheral port that can be easily isolated with the ADuM4160, whereas the speed of the downstream ports is handled by the hub controller. The hub controller converts peripherals of different speeds to match the upstream port speed. The circuit shown in Figure 1 shows how a two-port hub chip can be used to isolate two downstream host ports in a design that can be made fully compliant with the USB specification.

The ADuM4160 provides an inexpensive and easy to implement isolation buffer for medical and industrial peripherals. The challenge that must be met is to use this to create a fully com-pliant host port by pairing the ADuM4160 with a hub chip. As with isolating any peripheral device, the services that the ADuM4160 and hub provide are as follows:

1. Directly isolates, in the upstream, the USB D+ and D− lines of a hub chip, allowing the hub to manage the downstream host port activity.
2. Implements an automatic scheme for data flow of control that does not require external control lines.
3. Provides medical grade isolation.
4. Allows creation of one or more host ports that meet the USB-IF certification standards.
5. Supports full speed signaling rates.
6. Supports flexible power configurations.

The goal of the application circuit is to isolate a hub as if it were a full speed peripheral device. The hub or host function requires that 2.5 W of power be available to each downstream port. Power to run the downstream side of the isolator and power the hub and ports is provided as part of the solution. The application circuit is typical of many medical and industrial applications.

Many systems require low jitter multiple system clocks for mixed signal processing and timing. The circuit shown in Figure 1 interfaces the ADF4351 integrated phase-locked loop (PLL) and voltage-controlled oscillator (VCO) to the ADCLK948, which provides up to eight differential, low voltage, positive emitter coupled logic (LVPECL) outputs from one differential output of the ADF4351.

Modern digital systems often require many high quality clocks at logic levels that are different from the logic level of the clock source. Extra buffering may be required to guarantee accurate distribution to other circuit components without loss of integrity. The interface between the ADF4351 clock source ADCLK948 clock fanout buffer is described, and measurements show that the additive jitter associated with the clock fanout buffer is 75 fs rms.

The circuit shown in Figure 1 demonstrates isolation of an analog front end (18-bit, 5 MSPS AD7960 analog-to-digital converter (ADC)) at 600 Mbps using the ADN4651 LVDS isolator. An interposer board with the ADN4651 connects to the standard AD7960 evaluation platform, isolating the analog front end board from the high speed SDP-H1 system demonstration platform (EVAL-SDP-CH1Z). The SDP-H1 contains a Xilinx Spartan 6 FPGA to capture acquisitions and a ADSP-BF527 DSP to communicate with the PC.

Galvanic isolation of external interfaces is required in harsh environments for safety, functionality, or improved noise immunity. This includes analog front ends used in data acquisition modules for industrial measurement and control. Bandwidth requirements for converter interfaces are increasing, as trends such as Industry 4.0 and the Internet of Things (IoT) demand far more ubiquitous measurement and control, with greater speed and precision. This poses a challenge for isolation, because even standard digital isolators are limited to 150 Mbps operation.

For measurement and control applications in industrial environments, the benefits of such an isolated analog front-end implementation include:

• Ease of design due to the drop-in LVDS isolator with fully compliant input/output and ultralow jitter.
• High bandwidth of 600 Mbps to support increased ADC resolution and speed.
• Galvanic isolation for protection from mains voltages, isolated measurement of power supplies, or noise immunity from digital or power supply circuits.

The circuit in Figure 1 demonstrates an industry-leading solution to LVDS isolation at 600 Mbps using the ADN4651 dual-channel isolator.

The circuit shown in Figure 1 uses three photodiodes that are sensitive to different wavelengths (red, green, and blue), to measure light intensity levels over the light spectrum where plants are photosynthetically active. The measured results can be used to optimize the light source to match the requirements of the specific plants, enhance the growth rate, and minimize energy losses.

This circuit uses three precision current to voltage conversion stages that drive a single-supply, low power, low noise, 16-bit, Σ-Δ analog-to-digital converter (ADC) with three differential inputs.

The circuit deviates from the traditional approach by eliminating all mechanical and optical components, and uses only electrical components to achieve the same goal.

The circuit consumes less than 10 mW typical, making it ideal for battery operated portable field applications.

The printed circuit board (PCB) is designed in an Arduino-compatible shield form factor and interfaces to the EVAL-ADICUP360 Arduino-compatible platform board for rapid prototyping.

The circuit shown in Figure 1 is a cost effective, low power, multichannel data acquisition system that is compatible with standard industrial signal levels. The components are specifically selected to optimize settling time between samples, providing 18-bit performance at channel switching rates up to approximately 750 kHz.

The circuit can process eight gain-independent channels and is compatible with both single-ended and differential input signals.

The analog front end includes a multiplexer, programmable gain instrumentation amplifier (PGIA); precision analog-to-digital converter (ADC) driver for performing the single-ended to differential conversion; and an 18-bit, 1 MSPS PulSAR^® ADC for sampling the signal on the active channel. Gain configurations of 0.4, 0.8, 1.6, and 3.2 are available.

The maximum sample rate of the system is 1 MSPS. The channel switching logic is synchronous to the ADC conversions, and the maximum channel switching rate is 1 MHz. A single channel can be sampled at up to 1 MSPS with 18-bit resolution. Channel switching rates up to 750 kHz also provide 18-bit performance. The system also features low power consumption, consuming only 240 mW at the maximum ADC throughput rate of 1 MSPS.

It is important to provide fast and high resolution conversion information when sampling industrial level signals. Traditionally, the highest resolution analog-to-digital converters (ADCs) available at sampling rates up to 500 kSPS were 14 bit to 18 bit. The circuit shown in Figure 1 is a single-supply system optimized for sampling industrial level signals with a 24-bit, 250 kSPS sigma- delta (Σ-Δ) ADC. Each of the two differential or four pseudodifferential channels can be scanned at a rate up to 50 kSPS with 17.2 bits of noise-free code resolution.

This circuit solves the problem of acquiring and digitizing the standard industrial signal levels of ±5 V, ±10 V, and 0 V to 10 V with precision ADCs having low supply voltages by using an innovative differential amplifier with internal laser trimmed resistors to perform the attenuation and level shifting. Applications for the circuit include process controls (PLC/DCS modules), medical, and scientific multichannel instrumentation and chromatography.

The circuit shown in Figure 1 is a complete thermopile-based gas sensor using the nondispersive infrared (NDIR) principle. This circuit is optimized for CO₂ sensing, but can also accurately measure the concentration of a large number of gases by using thermopiles with different optical filters.

The printed circuit board (PCB) is designed in an Arduino shield form factor and interfaces to the EVAL-ADICUP360 Arduino-compatible platform board. The signal conditioning is implemented with the AD8629 and the ADA4528-1 low noise amplifiers and the ADuCM360 precision analog microcontroller, which contains programmable gain amplifiers, dual 24-bit Σ-Δ analog-to-digital converters (ADCs), and an ARM Cortex-M3 processor.