Пьезоэлектрические акселерометры

A data acquisition (DAQ) system measures real-world physical phenomenon, such as temperature, force, acceleration, or vibration, converting measurements into digital values for data processing, storage, or transmission to a remote location. A typical DAQ system is comprised of a sensor, analog filtering and signal conditioning circuitry, an analog-to-digital converter (ADC), and a digital controller. Components for a DAQ solution are selected on a per application basis. Some DAQ systems are designed to minimize the overall system dc error from the sensor, with fast settling filters for control loop or multiplexed applications. Others are designed to provide superior ac performance, with low distortion and flat frequency response.

The DAQ system shown in Figure 1 has simplified many of these design challenges into a single, flexible DAQ platform that can be used across a wide range of ac and dc applications.

The wide input voltage range, high input impedance, and high input common-mode voltage allows most sensors and signal sources to be connected directly to the input, without additional signal conditioning. The system has a programmable gain block for attenuation or amplification of the input signal to optimally utilize the input range of the ADC.

The dc and ac performance of this system have been optimized to provide exceptional performance across the entire analog input bandwidth. The low input bias current minimizes the dc error due to the output impedance of the sensor, and the high common-mode rejection ratio (CMRR) minimizes the impact of the common-mode noise pickup from the environment, especially when the sensor is located far from the DAQ system, which keeps the dc errors to a minimum, while not making sacrifices to the ac performance of the converter.

The ADC has fully programmable digital filters with adjustable bandwidth and data rate that can be tailor fit to specific system requirements. The analog filter of the system rejects frequencies at multiples of the sampling frequency, eliminating aliasing concerns.

The reference design shown in Figure 1 shows a high resolution, wide bandwidth, high dynamic range, Integrated Electronics Piezoelectric (IEPE)-compatible interface data acquisition (DAQ) system that interfaces with IC Piezoelectric (ICP^®)/IEPE sensors. The most common IEPE sensors are usually found in applications measuring vibration, but there are many IEPE sensors that measure parameters such as temperature, strain, shock, and displacement.

The focus of this circuit note is on the application of this solution to vibration applications, especially in the area of condition-based monitoring, but there is a large set of applications in instrumentation and industrial automation that use IEPE sensors in a similar way and that are served by similar signal chains.

Condition-based monitoring, in particular, uses sensor information to help predict changes in the condition of a machine. There are many methods of tracking the condition of a machine, but vibration analysis is the most commonly used method. By tracking the vibration analysis data over time, a fault or failure can be predicted, along with the source of the fault.

Vibration sensing in an industrial environment adds additional challenges because of the need for robust and reliable sensing methods. Knowing the condition of a machine helps increase efficiency and productivity and creates a safer working environment.

Most solutions that interface with piezoelectric sensors in the market are ac-coupled, lacking dc and subhertz measurement capabilities. The CN-0540 reference design is a dc-coupled solution in which dc and subhertz precision are achieved.

By looking at the complete data set from an IEPE vibration sensor in the frequency domain (dc to 50 kHz), the type and source of a machine fault can be better predicted using the position, amplitude, and number of harmonics found in the fast Fourier transform (FFT) spectrum.

The data acquisition board is an Arduino-compatible form factor that can be interfaced and powered directly from most Arduino-compatible development boards.

The ADAQ7768-1 is a 24-bit precision data acquisition (DAQ) μModule® system that encapsulates signal conditioning, conversion and processing blocks into one system in package (SiP) design that enables rapid development of highly compact, high performance precision DAQ systems.

The ADAQ7768-1 consists of:

• A low noise, low bias current, high bandwidth programmable gain instrumentation amplifier (PGIA) that is also capable of signal amplification and signal attenuation while maintaining high input impedance
• A fourth order, low noise, linear phase anti-aliasing filter
• A low noise, low distortion, high bandwidth ADC driver plus an optional linearity boost buffer
• A high-performance medium bandwidth 24-bit sigma delta ADC with programmable digital filter
• A low noise, low dropout linear regulator
• A reference buffers
• Critical passive components required for the signal chain

The ADAQ7768-1 supports fully differential input signal with a maximum range of ±12.6V. It has an input common mode voltage range of ±12V with excellent common mode rejection ratio (CMRR).

The input signal is fully buffered with very low input bias current of 2 pA typical. This allows easy input impedance matching and enables the ADAQ7768-1 to directly interface to sensors with high output impedance.

The seven pin-configurable gain settings offer additional system dynamic range and improved signal chain noise performance with input signals of lower amplitude.

A 4^th order low-pass analog filter combined with the user programmable digital filter ensures the signal chain is fully protected against the high frequency noise and out of band tones presented at the input node from aliasing back into the band of interest. The analog low pass filter is carefully designed to achieve high phase linearity and maximum in-band magnitude response flatness. Constructed with Analog Devices’s iPASSIVES™ technology, the resistor network used within the analog low-pass filter possess superior resistance matching in both absolute values and over temperature. As a result, the signal chain performance is maintained with minimum drift over temperature and the ADAQ7768-1 has an excellent device to device phase matching performance.

A high-performance ADC driver amplifier ensures the full settling of the ADC input at the maximum sampling rate. The driver circuit is designed to have minimum additive noise, error and distortion while maintaining stability. The fully differential architecture helps maximizing the signal chain dynamic range.

The analog to digital converter (ADC) inside the ADAQ7768-1 is a high performance, 24-bit precision, single channel Sigma-Delta converter with excellent AC performance and DC precision and the throughput rate of 256 kSPS from a 16.384 MHz MCLK.

An optional linearity boost buffer can further improve the signal chain linearity.

The ADAQ7768-1 is specified with the input reference voltage of 4.096V, but the device can support reference voltages ranging from VDD_ADC down to 1V.

The ADAQ7768-1 has two types of reference buffers. A pre-charge reference buffer to ease the reference input driving requirement or a full reference buffer to provide high impedance reference input. Both buffers are optional and can be turned off through register configuration. ADAQ7768-1 supports three clock input types: crystal, CMOS or LVDS.

Three types of digital low pass filters are available on the ADAQ7768-1. The wideband filter offers a filter profile similar to an ideal brick wall filter, making it a great fit for doing frequency analysis. The Sinc5 filter offers a low latency path with a smooth step response while maintaining a good level of aliasing rejection. It also supports an output data rate up to 1.024 MHz from a 16.384 MHz MCLK, making the Sinc5 filter ideal for low latency data capturing and time domain analysis. The Sinc3 filter supports a wide decimation ratio and can produce output data rate down to 50 SPS from a 16.384 MHz MCLK. This combined with the simultaneous 50/60Hz rejection post filter makes Sinc3 filter especially useful for precision DC measurement. All the three digital filters on the ADAQ7768-1 are FIR filters with linear phase response. The bandwidth of the filters, which directly corresponds to the bandwidth of the DAQ signal chain are fully programable through register configuration.

The ADAQ7768-1 also supports two device configuration methods. The user has the option to choose to configure the device via register write through its SPI interface, or through a simple hardware pin strapping method to configure the device to operate under a number of pre-defined modes.

A single SPI interface supports both the register access and the sample data readback functions. The ADAQ7768-1 always acts as a SPI slave. Multiple interface modes are supported with a minimum of three IO channels required to communicate with the device.

ADAQ7768-1 also features a suite of internal diagnostic functions that can detect a broad range of errors during operation to help improving the system reliability. The ADAQ7768-1 device has an operating temperature range of −40°C to +105°C and is available in a 12mm x 6mm, 84-ball BGA package with 0.8mm ball pitch. The ADAQ7768-1 utilizes only 75sq mm of board space, 10 times less than the discrete solution that utilizes 750sq mm.

Applications

• Universal input measurement platform
• Electrical Test and Measurement
• Sound and Vibration, Acoustic and Material Science R&D
• Control and Hardware in Loop Verification
• Condition monitoring for predictive maintenance
• Audio Test

AD7768/AD7768-4 – это восьмиканальный и четырехканальный Σ-Δ аналого-цифровые преобразователи (АЦП) одновременной выборки с Σ-Δ модулятором и цифровым фильтром в каждом канале, которые обеспечивают синхронную дискретизацию статических и динамических сигналов.

AD7768/AD7768-4 способны поддерживать динамический диапазон 108 дБ при максимальной полосе входного сигнала 110.8 кГц и обладает типичной интегральной нелинейностью (INL) ±2 ppm, напряжением смещения ±50 мкВ и погрешностью коэффициента усиления ±30 ppm.

При работе с AD7768/AD7768-4 пользователь может управлять соотношением входной полосы, частотой обновления выходных данных и рассеиваемой мощностью, выбирая один из трех рабочих режимов с учетом требований к уровню шума и энергопотреблению. Возможности конфигурирования позволяют превратить AD7768/AD7768-4 в переиспользуемую платформу для малопотребляющих модулей измерения статических сигналов и высокопроизводительных модулей измерения динамических сигналов.

AD7768/AD7768-4 имеют три рабочих режима: высокоскоростной режим (256 kSPS максимум, ширина полосы аналогового входа 110.8 кГц, 51.5 мВт на канал), медианный режим (128 kSPS максимум, ширина полосы аналогового входа 55.4 кГц, 27.5 мВт на канал) и экономичный режим (32 kSPS максимум, ширина полосы аналогового входа 13.8 кГц, 9.375 мВт на канал).

AD7768/AD7768-4 предоставляют широкие возможности цифровой фильтрации при помощи широкополосного фильтра нижних частот для устранения спектральных наложений, который обладает неравномерностью в полосе пропускания ±0.005 дБ, быстрым спадом передаточной характеристики и ослаблением 105 дБ на частоте Найквиста.

Широкополосный фильтр с линейной фазой может использоваться для измерений в частотной области. Этот фильтр имеет плоскую вершину (неравномерность ±0.005 дБ) в полосе пропускания от нуля до 102.4 кГц при 256 kSPS, от нуля до 51.2 кГц при 128 kSPS, и от нуля до 12.8 кГц при 32 kSPS.

AD7768/AD7768-4 также содержат фильтр с характеристикой sinc (sinc5), который обеспечивает малую задержку при изменении узкополосных сигналов с низким уровнем шума. Выбор используемых фильтров может осуществляться независимо для каждого из каналов.

При работе с фильтрами пользователь может расширять динамический диапазон, устанавливая коэффициент децимация равный ×32, ×64, ×128, ×256, ×512 или ×1024. За счет управления коэффициентом децимации достигается оптимизация характеристик шума в соответствии с требуемой полосой обработки входного сигнала.

В каждом канале АЦП интегрированы аналоговые схемы, упрощающие проектирование системы, например, буфер предварительного заряда на каждом аналоговом входе, который сокращает ток во входном канале, и буфер предварительного заряда для опорного напряжения, который сокращает входной ток и уровень импульсных бросков на опорных входах.

Компонент работает с напряжениями питания AVDD1A и AVDD1B, равными 5 В, напряжениями питания AVDD2A и AVDD2B в диапазоне от 2.25 В до 5.0 В и напряжением питания IOVDD  в диапазоне от 2.5 В до 3.3 В, либо 1.8 В (конкретные требования при работе с напряжением IOVDD, равным 1.8 В, см. в разделе "IOVDD 1.8 V  Operation" технического описания).

Устройство требует использования внешнего источника опорного напряжения; абсолютный диапазон входного опорного напряжения от 1 В до AVDD1 − AVSS.

Области применения

• Системы сбора данных: USB/PXI/Ethernet
• Контуры управления в измерительных устройствах и промышленном оборудовании
• Контрольно-измерительная аппаратура для аудиосигналов
• Контроль уровня вибраций и состояния механизмов
• Анализ качества напряжения в трехфазных цепях
• Звуковая эхолокация
• Прецизионная медицинская техника (приборы ЭЭГ/ЭМГ/ЭКГ)

AD7768-1 — это малопотребляющий, высококачественный аналого-цифровой преобразователь (АЦП) на основе Σ-Δ модулятора и цифрового фильтра, предназначенный для прецизионного преобразования статических и динамических сигналов. Компонент представляет собой одноканальную версию восьмиканального Σ-Δ АЦП с одновременной выборкой AD7768. AD7768-1 предоставляет пользователю единую конфигурируемую, переиспользуемую платформу для сбора данных. Эта платформа устанавливает новый стандарт статических и динамических погрешностей измерений и позволяет разработчикам промышленных и измерительных систем создавать разнообразные варианты устройств для схем с гальванической развязкой и без нее.

При частоте дискретизации 256 kSPS и использовании цифрового фильтра с конечной импульсной характеристикой (КИХ), обладающего малым уровнем пульсаций и полосой пропускания 110.8 кГц, AD7768-1 способен поддерживать динамический диапазон 108.5 дБ в сочетании с уровнем интегральной нелинейности (INL) ±1.1 ppm, погрешностью смещения  ±30 мкВ и погрешностью коэффициента усиления ±30 ppm.

Для работы с сигналами в расширенной полосе частот, при частоте Найквиста до 500 кГц, компонент имеет фильтр sinc5 с частотой среза по уровню −3 дБ, равной 204 кГц.

При работе с AD7768-1 пользователь имеет возможность управлять соотношением входной полосы, частоты выходных данных и рассеиваемой мощности. Эта особенность AD7768-1 позволяет производить динамический анализ изменяющегося входного сигнала, что делает компонент особенно полезным для универсальных систем сбора данных. Выбирая один из трех доступных режимов энергопотребления разработчик может достигнуть требуемых показателей уровня шума, минимизируя при этом потребляемую мощность. Архитектура AD7768-1 является уникальной в том смысле, что компонент превращается в конфигурируемую, переиспользуемую платформу как для малопотребляющих модулей измерения статических сигналов, так и для высокопроизводительных модулей измерения динамических сигналов.

AD7768-1 поддерживает оптимальный баланс статических и динамических характеристик, с одной стороны, и превосходной энергоэффективности, с другой стороны. Компонент имеет три рабочих режима, позволяющих управлять соотношением полосы входного сигнала и потребляемой мощности:

• В высокоскоростном режиме пользователь может выбрать фильтр с характеристикой sinc, обеспечивающий быстродействие до 256 kSPS и ширину полосы 52.2 кГц при потребляемой мощности 26.4 мВт, либо КИХ фильтр, обеспечивающий быстродействие до 256 kSPS и ширину полосы 110.8 кГц при потребляемой мощности 36.8 мВт.
• В медианном режиме пользователю доступен КИХ фильтр с быстродействием до 128 kSPS и шириной полосы 55.4 кГц при потребляемой мощности 19.7 мВт.
• В режиме низкой мощности пользователю доступен КИХ фильтр с быстродействием до 32 kSPS и шириной полосы 13.85 кГц при потребляемой мощности 6.75 мВт.

AD7768-1 обеспечивает обширные возможности цифровой фильтрации для удовлетворения широкого диапазона системных требований. Используя встроенные фильтры, пользователь может конфигурировать компонент для проведения измерений с жестким контролем погрешности коэффициента усиления по частоте, с линейной фазовой характеристикой (прямоугольный фильтр) или с малой задержкой (фильтры sinc5 или sinc3) для применения в контурах управления. Кроме того компонент можно сконфигурировать для измерения статических входных сигналов при помощи фильтра sinc3 с подавлением частоты сети 50 Гц или 60 Гц. Все фильтры имеют программируемый коэффициент децимации.

Для пользователей, которым необходима частота выходных данных, превышающая доступную при работе с КИХ фильтром с малой неравномерностью, имеется тракт с фильтром sinc5, работающий на частоте 1.024 МГц. Данный тракт обладает высоким шумом квантования и, поэтому, наиболее подходит для пользователей, которым требуется минимальная задержка при использовании в контурах управления, или которые реализуют собственные схемы цифровой фильтрации во внешней микросхеме программируемой логики (FPGA) или цифровом сигнальном процессоре (DSP).

Компонент предоставляет следующие варианты цифровых фильтров:

• КИХ фильтр с малой неравномерностью (неравномерность в полосе пропускания ±0.005 дБ на частотах до 102.4 кГц).
• Фильтр sinc5 с малой задержкой, обеспечивающий частоту данных до 1.024 МГц для увеличения скорости отклика в контурах управления.
• Фильтр sinc3 с малой задержкой, который является полностью программируемым и обеспечивает возможность подавления частоты 50 Гц/60 Гц.

Встроенные в AD7768-1 аналоговые схемы значительно упрощают процесс проектирования во всех возможных областях применения. Буфер предварительного заряда на каждом аналоговом входе уменьшает аналоговый входной ток по сравнению с конкурирующими продуктами, облегчая задачу для внешнего входного усилителя-драйвера.

Полнофункциональный буфер на входе опорного напряжения уменьшает входной ток, обеспечивая высокий импеданс для внешнего источника и устраняя влияние на внешний измерительный резистор, используемый в цепи опорного напряжения в схемах с относительными измерениями.

Компонент работает с напряжениями питания AVDD1 − AVSS = 5.0 В, AVDD2 − AVSS = 2.0 В ... 5.0 В и IOVDD − DGND = 1.8 В ... 3.3 В.

В режиме малой мощности выводы питания AVDD1, AVDD2 и IOVDD можно подключить к одному источнику напряжения 3.3 В.

Для работы с компонентом необходимо внешнее опорное напряжение. Допустимый диапазон входного опорного напряжения (REF_IN) — от  1 В до AVDD1 − AVSS.

Гарантированный рабочий температурный диапазон составляет от −40°C до +125°C. Компонент выпускается в 28-выводном корпусе LFCSP, имеющем габариты 4 мм × 5 мм.

Обратите внимание, что для обозначения многофункциональных выводов, например, XTAL2/MCLK, в техническом описании может использоваться как полное наименование, так и наименование отдельно взятой обсуждаемой функции, например, MCLK.

Области применения

• Платформа аналого-цифрового преобразования для проведения разнообразных измерений с различными типами датчиков
  • Измерение вибраций, акустические измерения и исследование материалов
  • Схемы управления и программно-аппаратная верификация (hardware in loop)
  • Мониторинг рабочего состояния при диагностическом обслуживании
  • Контрольно-измерительная аппаратура для электросетей
  • Измерение тока, измерение напряжения и тестирование аудиосистем
  • Клинические аппараты мониторинга основных показателей жизнедеятельности (ЭЭГ, ЭМГ и ЭКГ)
  • Модульные системы сбора данных с интерфейсами USB, PXI и Ethernet
  • Модульные системы сбора данных с межканальной развязкой

The AD7134 is a quad channel, low noise, simultaneous sampling, precision analog-to-digital converter (ADC) that delivers on functionality, performance, and ease of use.

Based on the continuous time sigma-delta (CTSD) modulation scheme, the AD7134 removes the traditionally required switched capacitor circuitry sampling preceding the Σ-Δ modulator, which leads to a relaxation of the ADC input driving requirement. The CTSD architecture also inherently rejects signals around the ADC aliasing frequency band, giving the device its inherent antialiasing capability, and removes the need for a complex external antialiasing filter.

The AD7134 has four independent converter channels in parallel, each with a CTSD modulator and a digital decimation and filtering path. The AD7134 enables simultaneous sampling of four separate signal sources, each supporting a maximum input bandwidth of 391.5 kHz and achieving tight phase matching between these four signal measurements. The high level of channel integration, together with its simplified analog front-end requirement, enables the AD7134 to provide a high density multichannel data acquisition solution in a small form factor.

The signal chain simplification property of the AD7134 also improves the system level performance through the reduction of noise, error, mismatch, and distortion that is normally introduced by the analog front-end circuitry.

The AD7134 offers excellent dc and ac performance. The bandwidth of each ADC channel ranges from dc to 391.5 kHz, making the device an ideal candidate for universal precision data acquisition solutions supporting a breadth of sensor types, from temperature and pressure to vibration and shock.

The AD7134 offers a large number of features and configuration options, giving the user the flexibility to achieve the optimal balance between bandwidth, noise, accuracy, and power for a given application.

An integrated asynchronous sample rate converter (ASRC) allows the AD7134 to precisely control the decimation ratio and, in turn, the output data rate (ODR) using interpolation and resampling techniques. The AD7134 supports a wide range of ODR frequencies, from 0.01 kSPS to 1496 kSPS with less than 0.01 SPS adjustment resolution, allowing the user to granularly vary sampling speed to achieve coherent sampling. The ODR value can be controlled through the ODR_VAL_INT_x and ODR_VAL_FLT_x registers (Register 0x16 to Register 0x1C, ASRC master mode), or using an external clock source (ASRC slave mode). The ASRC slave mode operation enables synchronous sampling between multiple AD7134 devices to a single system clock. The ASRC simplifies the clock distribution requirement within a medium bandwidth data acquisition system because it no longer requires a high frequency, low jitter master clock from the digital back end to be routed to each ADC.

The ASRC acts as a digital filter and decimates the oversampled data from the Σ-Δ modulator to a lower rate to favor higher precision. The ADC data is then further processed by one of the AD7134 user-selectable digital filter profiles to further reject the out of band signals and noises, and reduce the data rate to the final desired ODR value.

The AD7134 offers three main digital filter profile options: a wideband low ripple filter with a brick wall frequency profile and an ODR range from 2.5 kSPS to 374 kSPS that is suitable for frequency domain analysis, a fast responding sinc3 filter with an ODR range from 0.01 kSPS to 1496 kSPS that is suitable for low latency time domain analysis and low frequency high dynamic range input types, and a balanced sinc6 filter with an ODR range from 2.5 kSPS to 1.496 MSPS, offering optimal noise performance and response time.

The AD7134 is also capable of performing on-board averaging between two or four of its input channels. The result is a near 3 dB, if two channels are combined, or 6 dB, if all four channels are combined, improvement in dynamic range while maintaining the bandwidth.

The AD7134 supports two device configuration schemes: serial peripheral interface (SPI) and hardware pin configuration (pin control mode). The SPI control mode offers access to all the features and configuration options available on the AD7134. SPI control mode also enables access to the on-board diagnostic features designed to enable a robust system design. Pin control mode offers the benefit of simplifying the device configuration, enabling the device to operate autonomously after power-up operating in a standalone mode.

In addition to the optional SPI, the AD7134 has a flexible and independent data interface for transmitting the ADC output data. The data interface can act as either a bus master or a slave with various clocking options to support multiple communication bus protocols. The data interface also supports daisy-chaining and an optional minimum input/output (I/O) mode designed to minimize the number of digital isolator channels required in isolated applications.

The AD7134 has an operating ambient temperature range from 0°C to 85°C. The device is housed in an 8 mm × 8 mm, 56-lead lead frame chip scale package (LFCSP).

Note that throughout this data sheet, multifunction pins, such as FORMAT1/SCLK, are referred to either by the entire pin name or by a single function of the pin, for example, SCLK, when only that function is relevant.

Applications

• Electrical test and measurement
• Audio test
• 3-phase power quality analysis
• Control and hardware in loop verification
• Sonars
• Condition monitoring for predictive maintenance
• Acoustic and material science research and development

The ADG5421F is a dual SPST, low on resistance switch that features overvoltage protection, power-off protection, and overvoltage detection on the source pins.

When no power supplies are present, the switch remains in the off condition, and the switch inputs are high impedance. When powered, if the analog input signal levels on either of the Sx pins exceed V_DD or V_SS by the threshold voltage, V_T, both switches turn off together, and the open-drain fault flag (FF) pin pulls to a logic low. Input signal levels up to +60 V or −60 V relative to ground are blocked in both the powered and unpowered condition.

The switches turn on with a Logic 1 input and conduct equally well in both directions. The digital input is compatible with 1.8 V logic inputs over the full operating supply range.

APPLICATIONS

• Analog input and output modules
• Process control and distributed control systems
• Data acquisition
• Instrumentation
• Avionics
• Automatic test equipment
• Communication systems
• Relay replacement

The LTC2606/LTC2616/LTC2626 are single 16-, 14- and 12-bit, 2.7V-to-5.5V rail-to-rail voltage output DACs in a 10-lead DFN package. They have built-in high performance output buffers and are guaranteed monotonic.

These parts establish new board-density benchmarks for 16- and 14-bit DACs and advance performance standards for output drive and load regulation in single-supply, voltage-output DACs.

The parts use a 2-wire, I²C compatible serial interface. The LTC2606/LTC2616/LTC2626 operate in both the standard mode (clock rate of 100kHz) and the fast mode (clock rate of 400kHz). An asynchronous DAC update pin (LDAC) is also included.

The LTC2606/LTC2616/LTC2626 incorporate a power-on reset circuit. During power-up, the voltage outputs rise less than 10mV above zero scale; and after power-up, they stay at zero scale until a valid write and update take place. The power-on reset circuit resets the LTC2606-1/LTC2616-1/LTC2626-1 to midscale. The voltage outputs stay at midscale until a valid write and update take place.

Applications

• Mobile Communications
• Process Control and Industrial Automation
• Instrumentation
• Automatic Test Equipment

The AD8605, AD8606, and AD8608 are single, dual, and quad rail-to-rail input and output, single-supply amplifiers. They feature very low offset voltage, low input voltage and current noise, and wide signal bandwidth. They use the Analog Devices, Inc. patented DigiTrim^® trimming technique, which achieves superior precision without laser trimming.

The combination of low offsets, low noise, very low input bias currents, and high speed makes these amplifiers useful in a wide variety of applications. Filters, integrators, photodiode amplifiers, and high impedance sensors all benefit from the combination of performance features. Audio and other ac applications benefit from the wide bandwidth and low distortion. Applications for these amplifiers include optical control loops, portable and loop-powered instrumentation, and audio amplification for portable devices.

The AD8605, AD8606, and AD8608 are specified over the extended industrial temperature range (−40°C to +125°C). The AD8605 single is available in 5-lead SOT-23 and 5-ball WLCSP packages. The AD8606 dual is available in an 8-lead MSOP, an 8-ball WLSCP, and a narrow SOIC surface-mounted package. The AD8608 quad is available in a 14-lead TSSOP package and a narrow 14-lead SOIC package. The 5-ball and 8-ball WLCSP offer the smallest available footprint for any surface-mounted operational amplifier. The WLCSP, SOT-23, MSOP, and TSSOP versions are available in tape-and-reel only.

Applications

• Photodiode amplification
• Battery-powered instrumentation
• Multipole filters
• Sensors
• Barcode scanners
• Audio

The ADA4945-1 is a low noise, low distortion, fully differential amplifier with two selectable power modes. The device operates over a broad power supply range of 3 V to 10 V. The low dc offset, dc offset drift, and excellent dynamic performance of the ADA4945-1 makes it well suited for a variety of data acquisition and signal processing applications. The device is an ideal choice for driving high resolution, high performance successive approximation register (SAR) and Σ-Δ analog-to-digital converters (ADCs) on 4 mA of quiescent current (full power mode). The device can also be selected to operate on 1.4 mA of quiescent current (low power mode) to scale the power consumption to the desired performance necessary for an ADC drive application. The adjustable common-mode voltage allows the ADA4945-1 to match the input common-mode voltage of multiple ADCs. The internal common-mode feedback loop provides exceptional output balance, as well as suppression of even order harmonic distortion products.

With the ADA4945-1, differential gain configurations are achieved with a simple external feedback network of four resistors determining the closed-loop gain of the amplifier. The ADA4945-1 is fabricated using Analog Devices, Inc., proprietary, silicon germanium (SiGe), complementary bipolar process, enabling the device to achieve low levels of distortion with an input voltage noise of only 1.8 nV/√Hz (full power mode).

The ADA4945-1 is available in a RoHS-complaint, 3 mm × 3 mm, 16-lead LFCSP. The ADA4945-1 is specified to operate from −40°C to +125°C.

Applications

• Low power Σ-Δ, PulSAR^®, and SAR ADC drivers
• Single-ended to differential converters
• Differential buffers
• Medical imaging
• Process control
• Portable electronics

The LT3092 is a programmable 2-terminal current source. It requires only two resistors to set an output current between 0.5mA and 200mA. A multitude of analog techniques lend themselves to actively programming the output current. The LT3092 is stable without input and output capacitors, offering high DC and AC impedance. This feature allows operation in intrinsically safe applications.

The SET pin features 1% initial accuracy and low temperature coefficient. Current regulation is better than 10ppm/V from 1.5V to 40V.

The LT3092 can operate in a 2-terminal current source configuration in series with signal lines. It is ideal for driving sensors, remote supplies, and as a precision current limiter for local supplies.

Internal protection circuitry includes reverse-battery and reverse-current protection, current limiting and thermal limiting. The LT3092 is offered in the 8-lead TSOT-23, 3-lead SOT-223 and 8-lead 3mm × 3mm DFN packages.

Applications

• 2-Terminal Floating Current Source
• GND Referred Current Source
• Variable Current Source
• In-Line Limiter
• Intrinsic Safety Circuits

The ADR440/ADR441/ADR443/ADR444/ADR445 series is a family of XFET^® voltage references featuring ultralow noise, high accuracy, and low temperature drift performance. Using Analog Devices, Inc., patented temperature drift curvature correction and XFET (eXtra implanted junction FET) technology, voltage change vs. temperature nonlinearity in the ADR440/ADR441/ADR443/ADR444/ADR445 is greatly minimized.

The XFET references offer better noise performance than buried Zener references, and XFET references operate off low supply voltage headroom (500 mV). This combination of features makes the ADR440/ADR441/ADR443/ADR444/ADR445 family ideally suited for precision signal conversion applications in high-end data acquisition systems, optical networks, and medical applications.

The ADR440/ADR441/ADR443/ADR444/ADR445 family has the capability to source up to 10 mA of output current and sink up to −5 mA. It also comes with a trim terminal to adjust the output voltage over a 0.5% range without compromising performance.

The ADR440/ADR441/ADR443/ADR444/ADR445 family is available in 8-lead MSOP and narrow SOIC packages and offered in two electrical grades. All versions are specified over the extended industrial temperature range of −40°C to +125°C.

Applications

• Precision data acquisition systems
• High resolution data converters
• Battery-powered instrumentation
• Portable medical instruments
• Industrial process control systems
• Precision instruments
• Optical control circuits

The LTC6373 is a precision instrumentation amplifier with fully differential outputs which includes a closely matched internal resistor network to achieve excellent CMRR, offset voltage, gain error, gain drift, and gain nonlinearity. The user can easily program the gain to one of seven available settings through a 3-bit parallel interface (A2 to A0). The 8th state puts the part in shutdown which reduces the current consumption to 220μA. Unlike a conventional voltage feedback amplifier, the LTC6373 maintains nearly the same bandwidth across all its gain settings.

The LTC6373 features fully differential outputs to drive high performance, differential-input ADCs. The output common mode voltage is independently adjustable via the V_OCM pin. The combination of high impedance inputs, DC precision, low noise, low distortion, and high-speed differential ADC drive makes the LTC6373 an ideal candidate for optimizing data acquisition systems.

The LTC6373 is available in a 12-lead 4mm × 4mm DFN (LFCSP) package and is fully specified over the −40°C to 125°C temperature range.

Applications

• Data Acquisition Systems
• Biomedical Instrumentation
• Test and Measurement Equipment
• Differential ADC Drivers
• Single-Ended-to-Differential Conversion
• Multiplexed Applications