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Rarely Asked QuestionsManipulating MCU SPI Interface to Access a Nonstandard SPI ADC
Features and Benefits
- Precision ac and dc performance
- 8-/4-channel simultaneous sampling
- 256 kSPS maximum ADC ODR per channel
- 108 dB dynamic range
- 110.8 kHz maximum input bandwidth (−3 dB BW)
- −120 dB THD, typical
- ±2 ppm of full-scale range (FSR) integral nonlinearity (INL), ±50 μV offset error, ±30 ppm gain error
- Optimized power dissipation vs. noise vs. input bandwidth
- Selectable power, speed, and input bandwidth
- Fast (highest speed): 110.8 kHz BW, 51.5 mW per channel
- Median (half speed): 55.4 kHz BW, 27.5 mW per channel
- Low power (lowest power): 13.8 kHz BW, 9.375 mW per channel
- Input BW range: dc to 110.8 kHz
- Programmable input bandwidth/sampling rates
- Selectable power, speed, and input bandwidth
- CRC error checking on data interface
- Linear phase digital filter
- Low latency sinc5 filter
- Wideband brick wall filter: ±0.005 dB ripple to 102.4 kHz
- Analog input precharge buffers
- Power supply
- AVDD1 = 5.0 V, AVDD2 = 2.25 V to 5.0 V
- IOVDD = 2.5 V to 3.3 V or IOVDD = 1.8 V
- 64-lead LQFP package, no exposed pad
- Temperature range: −40°C to +105°C
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.
- 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
- High precision medical electroencephalogram (EEG)/electromyography (EMG)/electrocardiogram (ECG)
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (2)
The EVAL-AD7768FMCZ evaluation kit features the AD7768 24-bit, 256 kSPS, analog-to-digital converter (ADC). A 7 V to 9 V external bench top supply is regulated to 5 V and 3.3 V to supply the AD7768 and support components. The EVAL-AD7768FMCZ board connects to the USB port of the PC via a connection to the EVAL-SDP-CH1Z motherboard.
The AD7768 evaluation software fully configures the AD7768 device register functionality and provides dc and ac time domain analysis in the form of waveform graphs, histograms, and associated noise analysis for ADC performance evaluation.
The EVAL-AD7768FMCZ is an evaluation board that allows the user to evaluate the features of the ADC. The user PC software executable controls the AD7768 over a USB cable through the EVAL-SDP-CH1Z System Demonstration Platform (SDP). The AD7768 evaluation software requires PC running Windows® 7 to Windows 10 with a USB 2.0 port.
Full specifications on the AD7768 are available in the product data sheet, which should be consulted in conjunction with this user guide when working with the evaluation board.
Features & Benefits
- Full featured evaluation board for the AD7768
- PC control in conjunction with the SDP-H1 System Demonstration Platform (EVAL-SDP-CH1Z)
- PC software control and data analysis
- Time and frequency domain
- Standalone hardware capability
The Analog Devices, Inc., amplifier mezzanine card (AMC) analog-to-digital converter (ADC) driver evaluates the performance of amplifiers in 8-lead, single and dual SOIC, 6-lead single SOT23, 8-lead dual MSOP, and 16-lead LFCSP packages. This add on board can be inserted on ADC evaluation boards using its 7-pin header. Figure 1 shows the AMC mounted on an Analog Devices, Inc., ADC evaluation board.
The AMC can support any of Analog Devices operational amplifiers and ADC drivers in different packages. The user can configure the ADC driver as a Sallen-Key low-pass, high-pass, or band-pass filter, as a multiple feedback low-pass, high-pass, or band-pass filter, or as an inverting and noninverting operational amplifier. The user can also configure the AMC to drive a single-ended, fully differential, or a single-ended signal to a differential ADC.
Optimized power and ground planes ensure low noise and high speed operation. Component placement and power supply bypassing are optimized for maximum circuit flexibility and performance. The AMC evaluation board accepts 0402 or 0603 surface mount technology (SMT) components, 1206 bypass capacitors, and 2.54 mm headers.
All components are placed on the primary side. No components are placed on the secondary side.
Features & Benefits
- Enables quick breadboarding and prototyping
- User defined circuit configuration
- Easy connection to other ADC evaluation boards
Software & Systems Requirements
AD7768 Companion Parts
Recommended Driver Amplifiers
- For Fast Power Mode: ADA4945-1, ADA4896-2, ADA4940-1.
- For Low Power Mode: ADA4945-1, LTC6363, ADA4805-2.
- For Median Power Mode: ADA4945-1, ADA4807-2, ADA4940-1.
Recommended Current Source
Recommended Low Dropout Regulators and Switchers
Recommended Single Channel Converters
- Recommended single channel ADC: AD7768-1.
Analog Dialogue (6)
Press Releases (1)
Rarely Asked Questions (1)
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.