Circuit Note CN-0385 Devices Connected/Referenced 18-Bit, 2 MSPS, PulSAR, 7.0 mW ADC in AD4003 MSOP/QFN 10 MHz, 20 V/s, G = 1, 2, 4, 8, iCMOS AD8251 Programmable Gain Instrumentation Amplifier Circuits from the Lab reference designs are engineered and tested for quick and easy system integration to help solve todays Robust, Quad Channel Isolator with ADuM141E analog, mixed-signal, and RF design challenges. For more Output Enable and 1 Reverse Channel information and/or support, visit www.analog.com/CN0385. High Voltage, Latch-Up Proof, 8-Channel ADG5207 Differential Multiplexer Precision, Selectable Gain, Fully AD8475 Differential Amplifier 3.1 nV/Hz, 1 mA, 180 MHz, Rail-to-Rail ADA4807-2 Input/Output Dual Op Amp Isolated, Multichannel Data Acquisition System with PGIA for Single-Ended and Differential Industrial Level Signals The circuit can process eight gain-independent channels and is EVALUATION AND DESIGN SUPPORT compatible with both single-ended and differential input signals. Circuit Evaluation Boards The analog front end includes a multiplexer, programmable CN-0385 Circuit Evaluation Board (EVAL-CN0385-FMCZ) gain instrumentation amplifier (PGIA) precision analog-to- System Demonstration Platform (EVAL-SDP-CH1Z) Design and Integration Files digital converter (ADC) driver for performing the single-ended Schematics, Layout Files, Bill of Materials to differential conversion and an 18-bit, 2.0 MSPS precision PulSAR ADC for sampling the signal on the active channel. CIRCUIT FUNCTION AND BENEFITS Gain configurations of 0.4, 0.8, 1.6, and 3.2 are available. The circuit shown in Figure 1 is a cost effective, isolated, multi- The maximum sample rate of the system is 2 MSPS in turbo mode, channel data acquisition system that is compatible with standard and 1.5 MSPS in normal mode. The channel switching logic is industrial signal levels. The components are specifically selected synchronous to the ADC conversions, and the maximum channel to optimize settling time between samples, providing 18-bit switching rate is 1.5 MHz. A single channel can be sampled at performance at channel switching rates up to approximately up to 2 MSPS with 18-bit resolution in turbo mode. Channel 750 kHz. switching rates up to 750 kHz also provide 18-bit performance. Rev. 0 Circuits from the Lab reference designs 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. suitability and applicability for your use and application. Accordingly, in no event shall Analog Devices Tel: 781.329.4700 www.analog.com be liable for direct, indirect, special, incidental, consequential or punitive damages due to any cause Fax: 781.461.3113 2016 Analog Devices, Inc. All rights reserved. whatsoever connected to the use of any Circuits from the Lab circuits. (Continued on last page) CN-0385 Circuit Note ADR4540 5V +5V 5V NC1 TP VIN NC7 + 2.2F NC3 VOUT 1/2 2.2F ADA4807-2 GND NC5 +15V 1/2 4.99k ADA4807-2 + +15V 4.99k 1.8V 3.3V 5.5V 3.3V 12V VDD ADG5207 +5V ADuM3470 100 0.1F ADP2441 C7+ +V AD8251 S DA IN 100pF + CS 10F 100 AD8475 +V S C0+ 100pF 1.25k 1k 120pF IN 0.4 OUT FMC 1.25k SDI + 200 REF VDD VIO IN 0.8 OUT+ SDI 100 SCK +IN C0 VCOM SCK REF 200 AD4003 SDO 100pF DB +IN OUT +IN 0.8 IN SDO + + CNV 100 CNV +IN 0.4 GND 1.25k LOGIC 120pF C7 1k 100pF 1.25k V S DGND WR A1 A0 ADuM141E 1-OF-8 V S DECODER 5.5V +16V +15V 15V 5V ADP7118 ADP5070 SDI CPLD 15V SCK ADP7182 SDO 15V 16V CS 5.5V 3.3V ADP7118 5.5V 1.8V 5V ADP7118 ADP7118 Figure 1. Isolated Multichannel Data Acquisition Simplified Circuit (All Connections and Decoupling Not Shown) ADP2441 dc-to-dc converter generates 3.3 V for the digital CIRCUIT DESCRIPTION interface and the ADuM3470 primary supply input. The The circuit shown in Figure 1 is an isolated multichannel data ADP5070, ADP7118, and ADP7182 are used to generate acquisition signal chain consisting of a multiplexer, programmable positive and negative 15 V supplies. The ADP7118 is used to gain stage, ADC driver, and a fully differential, precision, successive generate 5 V, 3.3 V, and 1.8 V for the analog and digital power approximation register (SAR) ADC. The channel switching and supplies. The ADuM141E is selected for isolated high speed SPI gain switching is synchronized to the conversion period of the communication. It has 150 Mbps maximum data rate, low ADC. propagation delay, and low dynamic power consumption. The system can monitor up to eight channels using a single ADC, Component Selection reducing component count and cost compared to systems with The ADG5207 is a high voltage, latch-up proof, 8-channel one ADC per channel. Each channel can be configured with differential multiplexer. The ultralow capacitance and charge a different gain, allowing for flexibility of input ranges. It is injection of these switches make them ideal solutions for data manipulated by the complex programmable logic device (CPLD) acquisition and sample-and-hold applications, where low glitch which can be configured in the Labview graphical user interface and fast settling are required. A switching network at the inputs (GUI). The effective sample rate for each channel is equal to the of the ADG5207 adds compatibility with both single-ended and sample rate of the ADC divided by the total number of channels differential input signals. The active channel is selected via the being sampled. address pins of the device, which are controlled by the CPLD, The maximum sample rate of the system is limited by the settling and which can be configured in the GUI. time of the components (such as the programmable gain amplifier The AD8251 is a programmable gain instrumentation amplifier (PGA) bandwidth and RC filter bandwidth) in the analog front that provides selectable gain settings of 1, 2, 4, and 8. The higher end and the isolated digital interface clock rate which runs at gain settings boost smaller input signals to the full-scale input 75 MHz. Multiplexed signals are discontinuous in nature, resulting range of the AD4003. Each gain setting has its own suitable in potentially large voltage steps between sampling intervals. input range, which is shown in Table 1. The components in the signal chain must be given adequate time to settle to these steps before the ADC performs a conversion. Table 1. Input Range for Each of the Four Gain Configurations To maximize the time given for the signal to settle, the multiplexer Gain Full-Scale Input Range channels are switched immediately after the ADC begins a new 0.4 10.24 V conversion. 0.8 5.12 V The board power supply can take a dc input from 5 V to 12 V 1.6 2.56 V at the dc jack or 12 V from the SDP-H1 controller board. The 3.2 1.28 V Rev. 0 Page 2 of 13 VSS A0 A1 A2 EN GND 15142-001