AD8235ACBZ-EVALZ User Guide
UG-1478
Evaluating the AD8235 40 μA, Micropower Instrumentation Amplifier
FEATURES
Simple evaluation of the AD8235
CR2032 battery provision
On-board voltage reference using the LTC2063 low power amplifier
2 in × 1.35 in small form factor
APPLICATIONS
Fast and easy product evaluation and characterization Portable system applications
GENERAL DESCRIPTION
The AD8235ACBZ-EVALZ contains a CR2032 battery provision that is capable of powering up the AD8235 40 μA, micropower instrumentation amplifier and the LTC2063 low power operational amplifier. This feature allows the AD8235ACBZ-EVALZ to be a standalone board ready for product evaluation.
The AD8235ACBZ-EVALZ design allows the user to easily adjust the gain resistors and common discrete components on the board. The on-board male headers set the AD8235ACBZ-EVALZ to different configurations using the jumper shunt.
The AD8235ACBZ-EVALZ allows battery-powered configuration to showcase the portable nature of the AD8235. In battery-powered configuration, the LTC2063 acts as the voltage reference for the single-supply configuration.
For full details on the AD8235, see the AD8235 data sheet, which must be consulted in conjunction with this user guide when using the AD8235ACBZ-EVALZ.
EVALUATION BOARD PHOTOGRAPH
EVALUATION BOARD HARDWARE
SINGLE-SUPPLY OPERATION
A switch (S1) is provided on the AD8235ACBZ-EVALZ to select either a battery-powered configuration or an external supply configuration. The AD8235ACBZ-EVALZ is shipped in battery operated single-supply mode and is configured on the P2, P3, and P5 jumpers.
ON-BOARD AD8235
The AD8235 shutdown pin (SDN) can allow continuous operation of the AD8235, or this pin can interface to allow a microcontroller to be set when the AD8235 must operate in shutdown mode to conserve further energy.
Gain Adjustment
The AD8235 gain is pin-selectable where the gain (G) = 5 (default) and where the gain resistor (RG) is unpopulated. The AD8235 gain is resistor dependent. The resistor is connected between the RG pins. Table 1 provides calculated gains for the AD8235. See the
AD8235 data sheet for the gain equation.
Table 1. AD8235 Gain Resistor Values
| 1% Standard Value of RG (kΩ) | Calculated Gain |
| 422 210 140 105 84.5 28 9.31 4.42 2.15 |
6.0 7.0 8.0 9.0 10.0 20.0 50.1 100.0 200.3 |
COMPONENT LOCATIONS
See Figure 4 for the AD8235ACBZ-EVALZ component layout, connector locations, and male header locations.
LOAD RESISTOR
Although not required for normal operation, a load resistor can be inserted at Position R7.
Voltage Reference or Offset Adjustment
The default configuration of the AD8235ACBZ-EVALZ reference is set on the midsup ply level driven by the LTC2063.
The on-board voltage reference can be set at the P2 jumper to power up the LTC2063, and at the P3 jumper to connect the LTC2063 OUT pin to the AD8235 REF pin. See Figure 2 for the schematic design of the on-board voltage reference.
The LTC2063 features a shutdown control pin (SHDN) to disable the device. The 2063SD header on the AD8235ACBZ-EVALZ connects the LTC2063 SHDN pin to either the +VS pin or the GND1 pin of the AD8235ACBZ-EVALZ, and can interface to a microcontroller. See Table 2 for the LTC2063 options.
Table 2. Jumpers and Switch Configuration Options
| Jumper | Function | Default Position |
| 8235SD | Allows the AD8235 SDN pin to connect to either the +VS input or the −VS input on the AD8235ACBZ-EVALZ. |
EN |
| 2063SD | Allows the LTC2063 SHDN pin to connect to either the +VS input or the GND1 input on the AD8235ACBZ-EVALZ. |
EN |
| P1 | Connects the LTC2063 V + pin to the power supply to power up the LTC2063. | Installed |
| P2 | Allows the AD8235 REF pin to connect to either the LTC2063 OUT pin or the GND1 pin on the AD8235ACBZ-EVALZ. |
Position 1, connected to the LTC2063 OUT pin |
| P3 | Connects the AD8235 –VS pin to the GND1 pin on the AD8235ACBZ-EVALZ for single supply operation. |
Installed |
| S1 | Allows the AD8235ACBZ-EVALZ to be powered up by the CR2032 battery. | Position 1, battery not connected to the AD8235 +VS pin or the LTC2063 V + pin |
Table 3. AD8235ACBZ-EVALZ Input/Output Pins and Function Descriptions
| Input/Output Pin | Function |
| +VS and –VS GND1 and GND2 +IN and −IN REF VOUT |
Positive and negative rails of the amplifiers. Ground for the board. Positive and negative AD8235 inputs. Reference input for the AD8235. AD8235 output. |
AD8235ACBZ-EVALZ SCHEMATIC AND ARTWORK
ORDERING INFORMATION
BILL OF MATERIALS
Table 4.
| Reference Designator | Description | Manufacturer | Part Number |
| R5 R1, R2 R3, R4, R6 C6, C8 C1, C5, C7 P1, P3 P2, 8235SD, 2063SD S1 +VS, −VS, +IN, −IN, GND1, GND2, VOUT BAT1 U2 U1 |
Precision thin film chip resistor, 4.42 kΩ, R0603 Precision thin film chip resistors, 510 kΩ, R0603 Surface mount device (SMD) resistor chips, 0 Ω, R0603 X5R ceramic capacitors, 10 μF, R0603 X7R ceramic capacitors, 0.1 μF, R0603 2-position, male printed circuit board (PCB) headers 3-position, male PCB headers Subminiature single-pole double throw (SPDT) switch Turret style test points CR2032 battery holder Low bias current (IB), zero drift operational amplifier Micropower instrumentation amplifier, 40 μA |
Panasonic TE Connectivity Vishay TDK Kemet SAMTEC SAMTEC C&K Keystone Electronics Memory Protection Devices Analog Devices Analog Devices |
ERJ-3EKF4421V CPF0603B510KE1 CRCW0603000ZRT1 C1608X5R1A106K080AC C0603C104K4RAC TSW-102-08-G-S TSW-103-08-T-S JS102011JCQN 1502-2 BHX1-2032-PC LTC2063ISC6#TRMPBF AD8235ACBZ-P7 |
ESD Caution
ESD (electrostatic discharge) sensitive device. Charged devices and circuit boards can discharge without detection. Although this product features patented or proprietary protection circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
Legal Terms and Conditions
By using the evaluation board discussed herein (together with any tools, components documentation or support materials, the “Evaluation Board”), you are agreeing to be bound by the terms and conditions set forth below (“Agreement”) unless you have purchased the Evaluation Board, in which case the Analog Devices Standard Terms and Conditions of Sale shall govern. Do not use the Evaluation Board until you have read and agreed to the Agreement. Your use of the Evaluation Board shall signify your acceptance of the Agreement. This Agreement is made by and between you (“Customer”) and Analog Devices, Inc. (“ADI”), with its principal place of business at One Technology Way, Norwood, MA 02062, USA. Subject to the terms and conditions of the Agreement, ADI hereby grants to Customer a free, limited, personal, temporary, non-exclusive, non-sublicensable, non-transferable license to use the Evaluation Board FOR EVALUATION PURPOSES ONLY. Customer understands and agrees that the Evaluation Board is provided for the sole and exclusive purpose referenced above, and agrees not to use the Evaluation Board for any other purpose. Furthermore, the license granted is expressly made subject to the following additional limitations: Customer shall not (i) rent, lease, display, sell, transfer, assign, sublicense, or distribute the Evaluation Board; and (ii) permit any Third Party to access the Evaluation Board. As used herein, the term “Third Party” includes any entity other than ADI, Customer, their employees, affiliates and in-house consultants. The Evaluation Board is NOT sold to Customer; all rights not expressly granted herein, including ownership of the Evaluation Board, are reserved by ADI. CONFIDENTIALITY. This Agreement and the Evaluation Board shall all be considered the confidential and proprietary information of ADI. Customer may not disclose or transfer any portion of the Evaluation Board to any other party for any reason. Upon discontinuation of use of the Evaluation Board or termination of this Agreement, Customer agrees to promptly return the Evaluation Board to ADI. ADDITIONAL RESTRICTIONS. Customer may not disassemble, decompile or reverse engineer chips on the Evaluation Board. Customer shall inform ADI of any occurred damages or any modifications or alterations it makes to the Evaluation Board, including but not limited to soldering or any other activity that affects the material content of the Evaluation Board.
Modifications to the Evaluation Board must comply with applicable law, including but not limited to the RoHS Directive. TERMINATION. ADI may terminate this Agreement at any time upon giving written notice to Customer. Customer agrees to return to ADI the Evaluation Board at that time. LIMITATION OF LIABILITY. THE EVALUATION BOARD PROVIDED HEREUNDER IS PROVIDED “AS IS” AND ADI MAKES NO WARRANTIES OR REPRESENTATIONS OF ANY KIND WITH RESPECT TO IT. ADI SPECIFICALLY DISCLAIMS ANY REPRESENTATIONS, ENDORSEMENTS, GUARANTEES, OR WARRANTIES, EXPRESS OR IMPLIED, RELATED TO THE EVALUATION BOARD INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, TITLE, FITNESS FOR A PARTICULAR PURPOSE OR NONINFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS. IN NO EVENT WILL ADI AND ITS LICENSORS BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT, OR CONSEQUENTIAL DAMAGES RESULTING FROM CUSTOMER’S POSSESSION OR USE OF THE EVALUATION BOARD, INCLUDING BUT NOT LIMITED TO LOST PROFITS, DELAY COSTS, LABOR COSTS OR LOSS OF GOODWILL. ADI’S TOTAL LIABILITY FROM ANY AND ALL CAUSES SHALL BE LIMITED TO THE AMOUNT OF ONE HUNDRED US DOLLARS ($100.00). EXPORT. Customer agrees that it will not directly or indirectly export the Evaluation Board to another country, and that it will comply with all applicable United States federal laws and regulations relating to exports. GOVERNING LAW. This Agreement shall be governed by and construed in accordance with the substantive laws of the Commonwealth of Massachusetts (excluding conflict of law rules). Any legal action regarding this Agreement will be heard in the state or federal courts having jurisdiction in Suffolk County, Massachusetts, and Customer hereby submits to the personal jurisdiction and venue of such courts. The United Nations Convention on Contracts for the International Sale of Goods shall not apply to this Agreement and is expressly disclaimed.
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Documents / Resources
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ANALOG DEVICES AD8235 Micropower Instrumentation Amplifier [pdf] User Guide AD8235 Micropower Instrumentation Amplifier, AD8235, Micropower Instrumentation Amplifier, Instrumentation Amplifier, Amplifier |