Precision Signal Analyzers

The AD7768/AD7768-4 are 8-channel and 4-channel, simultaneous sampling sigma-delta (Σ-Δ) analog-to-digital converters (ADCs), respectively, with a Σ-Δ modulator and digital filter per channel, enabling synchronized sampling of ac and dc signals.

The AD7768/AD7768-4 achieve 108 dB dynamic range at a maximum input bandwidth of 110.8 kHz, combined with typical performance of ±2 ppm integral nonlinearity (INL), ±50 μV offset error, and ±30 ppm gain error.

The AD7768/AD7768-4 user can trade off input bandwidth, output data rate, and power dissipation, and select one of three power modes to optimize for noise targets and power consumption. The flexibility of the AD7768/AD7768-4 allows them to become reusable platforms for low power dc and high performance ac measurement modules.

The AD7768/AD7768-4 have three modes: fast mode (256 kSPS maximum, 110.8 kHz input bandwidth, 51.5 mW per channel), median mode (128 kSPS maximum, 55.4 kHz input bandwidth, 27.5 mW per channel) and low power mode (32 kSPS maximum, 13.8 kHz input bandwidth, 9.375 mW per channel).

The AD7768/AD7768-4 offer extensive digital filtering capabilities, such as a wideband, low ±0.005 dB pass-band ripple, antialiasing low-pass filter with sharp roll-off, and 105 dB attenuation at the Nyquist frequency.

Frequency domain measurements can use the wideband linear phase filter. This filter has a flat pass band (±0.005 dB ripple) from dc to 102.4 kHz at 256 kSPS, from dc to 51.2 kHz at 128 kSPS, or from dc to 12.8 kHz at 32 kSPS.

The AD7768/AD7768-4 also offer sinc response via a sinc5 filter, a low latency path for low bandwidth, and low noise measurements. The wideband and sinc5 filters can be selected and run on a per channel basis.

Within these filter options, the user can improve the dynamic range by selecting from decimation rates of ×32, ×64, ×128, ×256, ×512, and ×1024. The ability to vary the decimation filtering optimizes noise performance to the required input bandwidth.

Embedded analog functionality on each ADC channel makes design easier, such as a precharge buffer on each analog input that reduces analog input current and a precharge reference buffer per channel reduces input current and glitches on the reference input terminals.

The device operates with a 5 V AVDD1A and AVDD1B supply, a 2.25 V to 5.0 V AVDD2A and AVDD2B supply, and a 2.5 V to 3.3 V or 1.8 V IOVDD supply (see the 1.8 V IOVDD Operation section for specific requirements for operating at 1.8 V IOVDD).

The device requires an external reference; the absolute input reference voltage range is 1 V to AVDD1 − AVSS.

Applications

• Data acquisition systems: USB/PXI/Ethernet
• Instrumentation and industrial control loops
• Audio test and measurement
• Vibration and asset condition monitoring
• 3-phase power quality analysis
• Sonar
• High precision medical electroencephalogram (EEG)/electromyography (EMG)/electrocardiogram (ECG)

The AD7768/AD7768-4 are 8-channel and 4-channel, simultaneous sampling sigma-delta (Σ-Δ) analog-to-digital converters (ADCs), respectively, with a Σ-Δ modulator and digital filter per channel, enabling synchronized sampling of ac and dc signals.

The AD7768/AD7768-4 achieve 108 dB dynamic range at a maximum input bandwidth of 110.8 kHz, combined with typical performance of ±2 ppm integral nonlinearity (INL), ±50 μV offset error, and ±30 ppm gain error.

The AD7768/AD7768-4 user can trade off input bandwidth, output data rate, and power dissipation, and select one of three power modes to optimize for noise targets and power consumption. The flexibility of the AD7768/AD7768-4 allows them to become reusable platforms for low power dc and high performance ac measurement modules.

The AD7768/AD7768-4 have three modes: fast mode (256 kSPS maximum, 110.8 kHz input bandwidth, 51.5 mW per channel), median mode (128 kSPS maximum, 55.4 kHz input bandwidth, 27.5 mW per channel) and low power mode (32 kSPS maximum, 13.8 kHz input bandwidth, 9.375 mW per channel).

The AD7768/AD7768-4 offer extensive digital filtering capabilities, such as a wideband, low ±0.005 dB pass-band ripple, antialiasing low-pass filter with sharp roll-off, and 105 dB attenuation at the Nyquist frequency.

Frequency domain measurements can use the wideband linear phase filter. This filter has a flat pass band (±0.005 dB ripple) from dc to 102.4 kHz at 256 kSPS, from dc to 51.2 kHz at 128 kSPS, or from dc to 12.8 kHz at 32 kSPS.

The AD7768/AD7768-4 also offer sinc response via a sinc5 filter, a low latency path for low bandwidth, and low noise measurements. The wideband and sinc5 filters can be selected and run on a per channel basis.

Within these filter options, the user can improve the dynamic range by selecting from decimation rates of ×32, ×64, ×128, ×256, ×512, and ×1024. The ability to vary the decimation filtering optimizes noise performance to the required input bandwidth.

Embedded analog functionality on each ADC channel makes design easier, such as a precharge buffer on each analog input that reduces analog input current and a precharge reference buffer per channel reduces input current and glitches on the reference input terminals.

The device operates with a 5 V AVDD1A and AVDD1B supply, a 2.25 V to 5.0 V AVDD2A and AVDD2B supply, and a 2.5 V to 3.3 V or 1.8 V IOVDD supply (see the 1.8 V IOVDD Operation section for specific requirements for operating at 1.8 V IOVDD).

The device requires an external reference; the absolute input reference voltage range is 1 V to AVDD1 − AVSS.

APPLICATIONS

• Data acquisition systems: USB/PXI/Ethernet
• Instrumentation and industrial control loops
• Audio test and measurement
• Vibration and asset condition monitoring
• 3-phase power quality analysis
• Sonar
• High precision medical electroencephalogram (EEG)/electromyography (EMG)/electrocardiogram (ECG)

The AD7771 is an 8-channel, simultaneous sampling analog-to-digital converter (ADC). Eight full Σ-Δ ADCs are on-chip. The AD7771 provides an ultralow input current to allow direct sensor connection. Each input channel has a programmable gain stage allowing gains of 1, 2, 4, and 8 to map lower amplitude sensor outputs into the full-scale ADC input range, maximizing the dynamic range of the signal chain. The AD7771 accepts a V_REF voltage from 1 V up to 3.6 V. The analog inputs accept unipolar (0 V to V_REF) or true bipolar (±V_REF/2 V) analog input signals with 3.3 V or ±1.65 V analog supply voltages, respectively. The analog inputs can be configured to accept true differential or single-ended signals to match different sensor output configurations.

Each channel contains an ADC modulator and a sinc3/sinc5, low latency digital filter. A sample rate converter (SRC) is provided to allow fine resolution control over the AD7771 output data rate (ODR). This control can be used in applications where the ODR resolution is required to maintain coherency with 0.01 Hz changes in the line frequency. The SRC is programmable through the serial port interface (SPI). The AD7771 implements two different interfaces: a data output interface and SPI control interface. The ADC data output interface is dedicated to transmitting the ADC conversion results from the AD7771 to the processor. The SPI writes to and reads from the AD7771 configuration registers and for the control and reading of data from the successive approximation register (SAR) ADC. The SPI can also be configured to output the Σ-Δ conversion data.

The AD7771 includes a 12-bit SAR ADC. This ADC can be used for AD7771 diagnostics without having to decommission one of the Σ-Δ ADC channels dedicated to system measurement functions. With the use of an external multiplexer, which can be controlled through the three general-purpose input/output pins (GPIOs), and signal conditioning, the SAR ADC can validate the Σ-Δ ADC measurements in applications where functional safety is required. In addition, the AD7771 SAR ADC includes an internal multiplexer to sense internal nodes.

The AD7771 contains a 2.5 V reference and reference buffer. The reference has a typical temperature coefficient of ±10 ppm/°C.

The AD7771 offers two modes of operation: high resolution mode and low power mode. High resolution mode provides a higher dynamic range while consuming 16.6 mW per channel; low power mode consumes only 5.25 mW per channel at a reduced dynamic range specification.

The specified operating temperature range is −40°C to +105°C, although the device is operational up to +125°C.

Note that throughout this data sheet, certain terms are used to refer to either the multifunction pins or a range of pins. The multifunction pins, such as DCLK0/SDO, are referred to either by the entire pin name or by a single function of the pin, for example, DCLK0, when only that function is relevant. In the case of ranges of pins, AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3, and AVSS4.

Applications

• Power quality and measurement applications
• General-purpose data acquisition
• Electroencephalography (EEG)
• Industrial process control

The AD4003/AD4007/AD4011 are high accuracy, high speed, low power, 18-bit, Easy Drive, precision successive approximation register (SAR) analog-to-digital converters (ADCs) that operate from a single power supply, VDD. The reference voltage, V_REF, is applied externally and can be set independent of the supply voltage. The AD4003/AD4007/AD4011 power scales linearly with throughput.

Easy Drive features reduce both signal chain complexity and power consumption while enabling higher channel density. The reduced input current, particularly in high-Z mode, coupled with a long signal acquisition phase, eliminates the need for a dedicated ADC driver. Easy Drive broadens the range of companion circuitry that is capable of driving these ADCs (see Figure 2 in the data sheet).

Input span compression eliminates the need to provide a negative supply to the ADC driver amplifier while preserving access to the full ADC code range. The input overvoltage clamp protects the ADC inputs against overvoltage events, minimizing disturbances on the reference pin and eliminating the need for external protection diodes.

Fast device throughput up to 2 MSPS allows users to accurately capture high frequency signals and to implement oversampling techniques to alleviate the challenges associated with antialias filter designs. Decreased serial peripheral interface (SPI) clock rate requirements reduce digital input and output power consumption, broadens digital host options, and simplifies the task of sending data across digital isolation. The SPI-compatible serial user interface is compatible with 1.8 V, 2.5 V, 3 V, and 5 V logic by using the separate VIO logic supply.

APPLICATIONS

• Automated test equipment
• Machine automation
• Medical equipment
• Battery-powered equipment
• Precision data acquisition systems
• Instrumentation and control systems

The AD797 is a very low noise, low distortion operational amplifier ideal for use as a preamplifier. The low noise of 0.9 nV√Hz and low total harmonic distortion of -120 dB at audio bandwidths give the AD797 the wide dynamic range necessary for preamps in microphones and mixing consoles.

Furthermore, the AD797's excellent slew rate of 20 V/µs and 110 MHz gain bandwidth make it highly suitable for low frequency ultrasound applications.

The AD797 is also useful in IR and Sonar Imaging applications where the widest dynamic range is necessary. The low distortion and 16-bit settling time of the AD797 make it ideal for buffering the inputs to Sigma Delta ADCs or the outputs of high resolution DACs especially when they are used in critical applications such as seismic detection and spectrum analyzers. Key features such as a 50 mA output current drive and the specified power supply voltage range of ±5 to ±15 volts make the AD797 an excellent general purpose amplifier.

APPLICATIONS

• Professional audio preamplifiers
• IR, CCD, and sonar imaging systems
• Spectrum analyzers
• Ultrasound preamplifiers
• Seismic detectors
• Σ-Δ ADC/DAC buffers

The ADA4897-2 is a unity gain stable, low noise, rail-to-rail output, high speed voltage feedback amplifier that has a quiescent current of 3 mA. With the 1/f noise of 2.4 nV/√Hz at 10 Hz and a spurious-free dynamic range of −80 dBc at 2 MHz, the ADA4897-2 is an ideal solution in a variety of applications, including ultrasound, low noise preamplifiers, and drivers of high performance ADCs. Analog Devices, Inc., proprietary next generation SiGe bipolar process and innovative architecture enables such a high performance amplifier.

TheADA4897-2 has 230 MHz bandwidth, 120 V/µs slew rate, and settle to 0.1% in 45 ns. With a wide supply voltage range (3 V to 10 V), the ADA4897-2/ADA4897-1 is an ideal candidates for systems that require high dynamic range, precision, and high speed.

The ADA4897-2 is available in an 10-lead MSOP package and operates over the extended industrial temperature range of −40°C to +125°C.

• Low noise preamplifier
• Ultrasound amplifiers
• PLL Loop filters
• High performance ADC drivers
• DAC buffers

The AD1955 is a complete, high performance, single chip stereo digital audio playback system comprised of a multi-bit sigma-delta modulator, digital interpolation filters and a continuous-time differential current output DAC section. Unique to this audio DAC is the separate SACD (super audio CD) bit-stream and external digital filter interface, which allows users maximum system flexibility. The AD1955 supports 24-bits, 192 kHz sample rate and is designed for use in high-end SACD players, DVD-audio, home theater, automotive audio, digital mixing consoles, digital audio effect processors and sampling musical keyboards.

APPLICATIONS

• High-End DVD-Audio, SACD, CD, Home Theatre Systems
• Automotive Audio Systems, Sampling Musical Keyboards, Digital
• Mixing Consoles, Digital Audio Effects Processors

The circuit shown in Figure 1 provides a high dynamic range four channel simultaneous sampling system with high crosstalk isolation, flexible sampling rates, minimal external components, and simple interface connections to a DSP or FPGA. The circuit uses four AD7765 24-bit sigma-delta ADCs in a daisy chain configuration to minimize the number of connections to the digital host. The AD7765’s fully integrated differential input/output amplifier, and reference buffer significantly reduce the external component requirement.

Using the AD7765 configured in a simultaneous sampling configuration provides

• Channel-to-channel crosstalk isolation superior to that of solutions that integrate multiple 24-bit ADCs on a single chip.
• 112 dB dynamic range at 156 kSPS.
• Adaptable to greater or smaller channel counts.
• Allows multiple SYNC control (can be phase shifted with respect to each other).
• Dual decimation rates (128 and 256) and flexible sampling clock handles wide range of input bandwidths.

The Analog Devices, Inc., ADA4945-1CP-EBZ evaluation board allows the user to evaluate the performance of the ADA4945-1 fully differential amplifier. The ADA4945-1CP-EBZ evaluation board can be configured to accept either a single-ended or differential input signal.

The ADA4945-1CP-EBZ evaluation board uses several 2-pin and 3-pin headers to control various features of the ADA4945-1. Apply the proper jumpers to set the ADA4945-1 high and low output clamp levels, set the ADA4945-1 output common-mode voltage, choose high or low power mode for the ADA4945-1, and set the ADA4945-1 digital ground level.

Optimized power and ground planes ensure low noise and high speed operation. Component placement and power supply bypassing provide maximum circuit flexibility and performance. The ADA4945-1CP-EBZ evaluation board accepts 0402 surface mount technology (SMT) components, 0805 bypass capacitors, and 2.54 mm headers.

Input and output signals are brought to and from the board via 50 Ω, side launch Subminiature Version A (SMA) connectors.

Full specifications on the ADA4945-1 are available in the ADA4945-1 data sheet. Consult the data sheet in conjunction with this user guide when working with the ADA4945-1CP-EBZ evaluation board.