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ADI engineers share their lab work with you in this
‘Circuits from the Lab’ Circuit Note.
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for more details.
CN0042
ADI engineers share their lab work with you in this ‘Circuits from the Lab’ Circuit Note. You can combine these product pairings quickly and with confidence. Please review the disclaimer at the bottom of the page for more information.
Copyright 2008, Analog Devices, Inc. All rights reserved. "Circuits from the Lab" from Analog Devices have been designed and built by Analog Devices engineers. Standard engineering practices have been employed in the design and construction of each circuit, and their function and performance have been tested and verified in a lab environment at room temperature. However, you are solely responsible for testing the circuit and determining its suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause whatsoever connected to the use of any "Circuits from the Lab". Circuit variations described in the Common Variations section of the document have not necessarily also been built and tested.
"Circuits from the Lab" are intended only for use with Analog Devices products and are the intellectual property of Analog Devices or its licensors. While you may use the "Circuits from the Lab" in the design of your product, no other license is granted by implication or otherwise under any patents or other intellectual property by application or use of the "Circuits from the Lab". Information furnished by Analog Devices is believed to be accurate and reliable. However, "Circuits from the Lab" are supplied "as is" and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability, noninfringement or fitness for a particular purpose and no responsibility is assumed by Analog Devices for their use, nor for any infringements of patents or other rights of third parties that may result from their use. Analog Devices reserves the right to change any "Circuits from the Lab" at any time without notice, but is under no obligation to do so. Trademarks and registered trademarks are the property of their respective owners.
Driving the AD7366/AD7367 Bipolar SAR ADC in Low-Distortion DC-Coupled
(CN0042)| Circuit Types: | ADC Circuit/Driver |
| Applications: | Instrumentation, Medical, Process Control |
The circuit described in this document provides single-ended, low-distortion sampling of an industrial level, dc-coupled signal. The driver circuit shown in Figure 1 is optimized for applications requiring best distortion performance. Maximum AD7366/AD7367 performance is achieved by providing adequate settling time and low impedance in the circuit.
Driving the AD7366/AD7367 Bipolar SAR ADC in Low-Distortion DC-Coupled (CN0042)
Figure 1: Typical Connection Diagram with the AD8021 for Driving the Analog Inputs of the AD7366/AD7367
(Simplified Schematic, Decoupling and All Connections Not Shown)
|
|
Figure 1: Typical Connection Diagram with the AD8021 for Driving the Analog Inputs of the AD7366/AD7367
(Simplified Schematic, Decoupling and All Connections Not Shown) |
The AD7366 and the AD7367 are, respectively, 12-bit and 14-bit, 1 MSPS, 2-channel, simultaneous sampling SAR ADCs. These devices have a total of four analog multiplexed inputs (two per channel), which operate in single-ended mode. The analog input range on the AD7366/AD7367 is programmable and can support ±10 V, ±5 V, and 0 V to 10 V using the internal 2.5 V reference. An analog input range of ±12 V requires a 3 V external reference.
The AD7366/AD7367 are fabricated on the Analog Devices, Inc., industrial CMOS process (iCMOS), which is a technology platform combining the advantages of low and high voltage CMOS. The input circuits of the AD7366/AD7367 operate on VDD and VSS voltages of ±12 V nominal, while the rest of the ADC operates on an AVCC, a DVCC, and a VDRIVE of +5 V. The iCMOS process, therefore, allows the AD7366/AD7367 to accept high voltage bipolar signals in addition to reducing power consumption and package size.
In applications where the signal source has high impedance, analog input signals should be buffered before being applied to the inputs of the AD7366/AD7367 because large source impedances significantly affect the ac performance of the ADC. The choice of the op amp used to drive the inputs is a function of the particular application and depends on the analog input voltage range selected. The driver amplifier must be able to settle for a full-scale step to a 14-bit level (0.0061%) for the AD7367 or a 12-bit level (0.024%) for the AD7366 in less than the specified acquisition time of 140 ns.
The AD8021 high performance voltage feedback op amp is an ideal choice as a single-ended input buffer/driver for the AD7366/AD7367 due to its exceptionally high performance, high speed, low noise, and low distortion performance. It also meets the above stated requirement when operating in single-ended mode. Figure 1 shows the configuration of the AD7366/ AD7367 with the AD8021 in a single-ended configuration. The AD8021 needs an external compensating NPO type capacitor (CCOMP), as indicated in Figure 1. The AD8021 is connected in the noninverting mode with a gain of 2. The AD7366/AD7367 programmable bipolar input voltage ranges (referenced to the input of the AD8021) are ±5 V and ±2.5 V.
The circuit must be constructed on a multilayer PC board with a large area ground plane. Proper layout, grounding, and decoupling techniques must be used to achieve optimum performance (see MT-031 Tutorial, MT-101 Tutorial, and the AD7366/AD7367 evaluation board layout).
Contributed October, 2008
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AD7366:
True Bipolar Input, Dual 12-Bit, 2-Channel, Simultaneous Sampling SAR ADCThe AD7366/AD73671 are dual 12-bit/14-bit, high speed, low power, successive approximation analog-to-digital converters (ADCs) that feature throughput rates up to 1 MSPS. The device contains two ADCs, each preceded by a 2-channel multiplexer, and a low noise, wide bandwidth track-and-hold amplifier.
The AD7366/AD7367 are fabricated on the Analog Devices, Inc., industrial CMOS More
Data Sheet Rev B, 08/2009 (pdf 634kB)
Data Sheet Rev B, 08/2009 (pdf 634kB) -
AD7367:
True Bipolar Input, Dual 14-Bit, 2-Channel, Simultaneous Sampling SAR ADCThe AD7366/AD73671 are dual 12-bit/14-bit, high speed, low power, successive approximation analog-to-digital converters (ADCs) that feature throughput rates up to 1 MSPS. The device contains two ADCs, each preceded by a 2-channel multiplexer, and a low noise, wide bandwidth track-and-hold amplifier.
The AD7366/AD7367 are fabricated on the Analog Devices, Inc., industrial CMOS More
Data Sheet Rev B, 08/2009 (pdf 634kB)
Data Sheet Rev B, 08/2009 (pdf 634kB) -
AD8021:
Low Noise, High Speed Amplifier for 16-Bit SystemsThe AD8021 is an exceptionally high performance, high speed voltage feedback amplifier that can be used in 16-bit resolution systems. It is designed to have both low voltage and low current noise (2.1 nV/√Hz typical and 2.1 pA/√Hz typical) while operating at the lowest quiescent supply current (7 mA @ ±5 V) among today's high speed, low noise op amps. The AD8021 operates over a wide range of More
Data Sheet Rev F, 05/2006 (pdf 579kB)
Data Sheet Rev F, 05/2006 (pdf 579kB) -
AD845:
Precision, 16 MHz CBFET Op AmpThe AD845 is a fast, precise, N channel JFET input, monolithic operational amplifier. It is fabricated using Analog Devices' complementary bipolar (CB) process. Advanced laser-wafer trimming technology enables the very low input offset voltage and offset voltage drift performance to be realized. This precision, when coupled with a slew rate of 100 V/µs, a stable unity-gain bandwidth of 16 MHz, and More
Data Sheet Rev E, 10/2003 (pdf 211kB)
Data Sheet Rev E, 10/2003 (pdf 211kB) -
AD8610:
Precision, Low Input Bias Current, Wide BW JFET Op Amp (Single)The AD8610 (single) and AD8620 (dual) are very high precision JFET input amplifiers featuring ultralow offset voltage and drift, very low input voltage and current noise, very low input bias current, and wide bandwidth. Unlike many JFET amplifiers, the AD8610 input bias current is low over the entire operating temperature range. The AD8610 is stable with capacitive loads of over 1000 pF in More
Data Sheet Rev F, 05/2008 (pdf 3864kB)
Data Sheet Rev F, 05/2008 (pdf 3864kB) -
AD8638:
16 V Auto-Zero, Rail-to-Rail Output Operational AmplifierThe AD8638/AD8639 are single and dual wide bandwidth, auto-zero amplifiers featuring rail-to-rail output swing and low noise. These amplifiers have very low offset, drift, and bias current. Operation is fully specified from 5 V to 16 V single supply (±2.5 V to ±8 V dual supply).
The AD8638/AD8639 provide benefits previously found only in expensive zero-drift or chopper-stabilized More
Data Sheet Rev E, 06/2009 (pdf 632kB)
Data Sheet Rev E, 06/2009 (pdf 632kB) -
OP07D:
Ultralow Offset Voltage Operational AmplifierThe OP07D is a low cost option of the OP07 family with voltage offset performance of 150 µV max. The OP07D is a precision, ultralow offset amplifier. It integrates low power (1.1 mA typical), low input bias current (±1 nA maximum), and high CMRR/PSRR (130 dB). Operation is fully specified from ±5 V to ±15 V supply.
The OP07D provides higher accuracy than industry-standard OP07-type More
Data Sheet Rev 0, 01/2006 (pdf 332kB)
Data Sheet Rev 0, 01/2006 (pdf 332kB) -
OP177:
Ultra-Precision Operational AmplifierThe OP177 features one of the highest precision performance of any op amp currently available. Offset voltage of the OP177 is only 25 μV maximum at room temperature. The ultralow VOS of the OP177 combines with its exceptional offset voltage drift (TCVOS) of 0.1 μV/°C maximum to eliminate the need for external VOS adjustment and increases system accuracy over temperature.
The OP177 More
Data Sheet Rev F, 03/2009 (pdf 340kB)
Data Sheet Rev F, 03/2009 (pdf 340kB)
Evaluation Boards
- ADIsimPower™ Voltage Regulator Design Tool This tool supports buck converter designs OPTIMIZED for efficiency, PCB spa...
- Converter Evaluation and Development Platform
- EVAL-AD7366/AD7367: Evaluation Board for Single-Ended Input, Simultaneous Sampling, 12-/14-Bit ADC Data Sheet
- Universal High Speed Op Amp Evaluation Boards The Universal Evaluation Board allows the user to quickly and easily evalua...
- ADIsimOpAmp™ This tool will help with the selection, evaluation and troubleshooting of v...
- ADIsimPower™ Voltage Regulator Design Tool This tool supports buck converter designs OPTIMIZED for efficiency, PCB spa...
- OpAmp Stability An applet for demonstrating stability effects in opamp buffers.
- AD8021 SPICE Macro-Model
- AD845 SPICE Macro-Model
- AD8610 SPICE Models