EPN April 2012 - (Page 33)

Circuit Note CN-0235 Test Results An important measure of the performance of the circuit is the amount of noise in the final output voltage measurement. Figure 6 shows a histogram of 10,000 measurement samples taken for the VIN3−VIN2 channel. This data was taken with the CN0235 Evaluation Board connected to the EVALSDP-CB1Z System Demonstration Platform (SDP-B) evaluation board. Details of the setup are described in the Circuit Evaluation and Test section of this circuit note. Twelve Li-Ion batteries were connected to the input screw terminals. Note that there are only a small percentage of codes that fall outside the primary bin due to noise. Figure 6 and Figure 7 show 3 LSBs peak-to-peak noise, corresponding to approximately 0.5 LSBs rms. A complete design support package for this circuit note can be found at www.analog.com/CN0235-DesignSupport. (zip file) To view both diagrams at a larger size please click here. connectors, allowing for the quick setup and evaluation of the circuit’s performance. The EVAL-CN0235-SDPZ board contains the circuit to be evaluated, as described in this note, and the SDP-B evaluation board is used with the CN0235 evaluation software to capture the data from the EVAL-CN0235-SDPZ circuit board. Equipment Needed • PC with a USB port and Windows® XP or Windows Vista® (32-bit), or Windows® 7 (32-bit) • EVAL-CN0235-SDPZ circuit evaluation board • EVAL-SDP-CB1Z SDP-B evaluation board • CN0235 SDP evaluation software • Power supply: +6 V, or +6 V “wall wart” • Li-Ion batteries or precision dc supply Getting Started Load the evaluation software by placing the CN0235 Evaluation Software disc in the CD drive of the PC. Using “My Computer,” locate the drive that contains the evaluation software. Functional Block Diagram See Figure 1 of this circuit note for the circuit block diagram, and the file “EVALCN0235-SDPZ-SCH-RevA.pdf ” for the circuit schematics. This file is contained in the CN0235 Design Support Package. Setup Connect the 120-pin connector on the EVAL-CN0235-SDPZ circuit board to the connector marked “CON A” on the EVAL-SDP-CB1Z evaluation (SDP-B) board. Nylon hardware should be used to firmly secure the two boards, using the holes provided at the ends of the 120-pin connectors. With power to the supply off, connect a +6 V power supply to the pins marked “+6 V” and “GND” on the board. If available, a +6 V “wall wart” can be connected to the barrel connector on the board and used in place of the +6 V power supply. The only other connections required are to the lithium ion battery stack. The battery stack can be simulated with a resistor divider, which is driven by a precision dc supply voltage. Connect the USB cable supplied with the SDP-B board to the USB port on the PC. Note: Do not connect the USB cable to the mini USB connector on the SDP-B board at this time. Test Apply power to the +6 V supply (or “wall wart”) connected to EVAL-CN0235-SDPZ circuit board. Launch the evaluation software and connect the USB cable from the PC to the USB mini-connector on the SDP-B board. Once USB communications are established, the SDP-B board can be used to send, receive, and capture serial data from the EVAL-CN0235-SDPZ board. Information regarding the SDP-B board can be found in the SDP-B User Guide. Figure 6. Histogram of Codes for 10,000 Samples, VIN4 – VIN3 of Device 0 Figure 7. Histogram for 10,000 Samples, VIN4 - VIN3 of Device 1 COMMON VARIATIONS The circuit is proven to work with good stability and accuracy. Other combinations of isolated channels can be used with the iCoupler isolation products. CIRCUIT EVALUATION AND TEST This circuit uses the EVAL-CN0235-SDPZ circuit board and the EVAL-SDP-CB1Z System Demonstration Platform (SDP-B) evaluation board. The two boards have 120-pin mating Circuits from the Lab circuits 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 circuits 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 circuits. Information furnished by Analog Devices is believed to be accurate and reliable. However, Circuits from the Lab circuits 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 circuits at any time without notice but is under no obligation to do so. ©2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. www.analog.com http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-SDP-CB1Z http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-SDP-CB1Z http://www.analog.com/CN0235-DesignSupport http://www.analog.com/CN0235 http://www.analog.com/CN0235-DesignSupport http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-SDP-CB1Z http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-CN0235-SDPZ http://www.analog.com/EVAL-SDP-CB1Z http://www.analog.com/SDP http://www.analog.com

Table of Contents for the Digital Edition of EPN April 2012

Cover
RS Components
Contents
Edito
Bergquist
Contents Web
LEMO
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PCIM
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Test corner
Power perspective
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EPN April 2012