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information and/or support, visit www.analog.com/CN0336. Fax: 781.461.3113 ©2014 Analog Devices, Inc. All rights reserved. 300 kSPS data acquisition system utilizing only three active devices. often encountered in harsh industrial environments. Figure 1. 4 mA to 20 mA Single Supply Analog to Digital Conversion with Isolation (All Connections and Decoupling Not Shown)
reverse connection of the input current source. ranges as described later in this circuit note. less than 1 mA, and a narrower temperature range. input op amp is 0.1 V to 2.4 V . internal 2.5 V voltage reference of the AD7091R (U3) ADC. dissipation is only 9.2 mW on a 3.3 V supply. lower than any competitive ADC currently available in the market. AD7091R is available in a small footprint 10-lead MSOP. operating on a 3.3 V supply. ADuM5401 with a 7 MHz clock is approximately 140 mW. limits the upper clock frequency to 1/120 ns = 8.3 MHz. 16 clock cycles for the SPI interface data transfer. and a maximum sampling rate of 300 kSPS is recommended. (Digilent Pmod Specifications). Figure 2. Current-to-Voltage Converter and Level Shifting Circuit
The transfer function is obtained from the superposition principle. ensure that the required headroom is preserved. substitution and resistor tolerances. The full-scale drift of 30 ppm/°C corresponds to 0.003%FSR/°C. are eliminated by the calibration procedure. 4.5 ppm/°C typical and 25 ppm/°C maximum. buffer is referenced to 2.5 V and is also approximately 2 ppm/°C. not include the ±1 LSB integral nonlinearity error of the AD7091R. Table 1. Error Due to Temperature Drift
the input, and the ADC output code is recorded as Code_1. components, and real circuit transfer function without calibration. tolerance. The test results do not include temperature changes. which approximately corresponds to 1 LSB error of the ADC. Figure 3. Circuit Test Error Before and After Room Temperature Calibration MT-101 Tutorial for information on decoupling techniques. 16, as close to the chip pads as possible. www.analog.com/CN0336-DesignSupport. practices. High voltage testing beyond 2500 V is not recommended. tested) or certified for safety. applications for this circuit. input circuit can be simplified, as is shown in Figure 4.
Rev. A | Page 7 of 7 LEARN MORE CN0336 Design Support Package: http://www.analog.com/CN0336-DesignSupport Chen, Baoxing, John Wynne, and Ronn Kliger. High Speed Digital Isolators Using Microscale On-Chip Transformers, Analog Devices, 2003 Chen, Baoxing. iCoupler® Products with isoPower™ Technology: Signal and Power Transfer Across Isolation Barrier Using Microtransformers, Analog Devices, 2006 Ghiorse, Rich. Application Note AN-825, Power Supply Considerations in iCoupler® Isolation Products, Analog Devices Krakauer, David. “Digital Isolation Offers Compact, Low-Cost Solutions to Challenging Design Problems.”Analog Dialogue. Volume 40, December 2006. MT-031 Tutorial, Grounding Data Converters and Solving the Mystery of "AGND" and "DGND," Analog Devices MT-101 Tutorial, Decoupling Techniques, Analog Devices Wayne, Scott. “iCoupler ® Digital Isolators Protect RS-232, RS- 485, and CAN Buses in Industrial, Instrumentation, and Computer Apps, Analog Dialogue, Volume 39, Number 4, 2005. Data Sheets and Evaluation Boards AD8606 Data Sheet AD7091R Data Sheet ADuM5401 Data Sheet
REVISION HISTORY
3/14—Rev. 0 to Rev. A 2/14—Revision 0: Initial Version (Continued from first page) Circuits from the Lab reference designs 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 reference designs 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 reference designs. Information furnished by Analog Devices is believed to be accurate and reliable. However, Circuits from the Lab reference designs 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 reference designs at any time without notice but is under no obligation to do so. ©2014 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. CN11650-0-3/14(A)