AD7864_EvalBoard| Application Note
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Evaluation Board for 4 Channel, Simultaneous Sampling Hi-Speed, 12-Bit ADC EVAL-AD7864CB
OPERATING THE AD7864 EVALUATION BOARD Power Supplies
FEATURES Full-Featured Evaluation Board for the AD7864 EVAL-CONTROL BOARD Compatible Stand Alone Capability On-Board Analog Buffering and Reference Various Linking Options PC Software for Control and Data Analysis when used with EVAL-CONTROL BOARD INTRODUCTION
When using this evaluation board with the EVAL-CONTROL BOARD all supplies are provided from the EVALCONTROL BOARD through the 96 way connector. When using the board as a stand alone unit external supplies must be provided. This evaluation board has seven power supply inputs: AVDD, AGND, +12V, -12V, AGND, DVDD and DGND. +5V must be connected to the AVDD input to supply the AD7864 AVDD pin and the AD780 voltage reference. +12V and -12V are used to supply the OP467 quad op-amp. The DVDD input can be used to supply a separate +5V for the AD7864 DVDD pin and the DGND input must be tied to 0V. Aternatively the DVDD input can be supplied from the same +5V as the AVDD supply by placing LK15 in position "A". The supplies are decoupled to the relevant ground plane with 10uF tantalum and 0.1uF multilayer ceramic capacitors at the point where they enter the board. The supply pins of the quad op-amp and reference are also decoupled to AGND with 10uF tantalum and a 0.1uF ceramic capacitor. The AD7864 AVDD supply pin is de
coupled to AGND with 47uF tantalum and 0.1uF multilayer ceramic capacitors. Extensive ground planes are used on this board to minimize the effect of high frequency noise interference. There are two ground planes, AGND and DGND. These are connected at one location close to the AD7864.
This Technical Note describes the evaluation board for the AD7864 high speed, low power, four-channel simultaneous sampling 12-bit A/D converter that operates from a single 5 V supply. Full data on the AD7864 is available in the AD7864 data sheet available from Analog Devices and should be consulted in conjunction with this Technical Note when using the Evaluation Board. On-board components include an AD780 which is a pin programmable +2.5V or +3V ultra high precision bandgap reference and an OP467 quad op-amp used to buffer the analog inputs. There are various link options which are explained in detail on page 2. Interfacing to this board is through a 96-way connector. This 96-way connector is compatible with the EVAL-CONTROL BOARD which is also available from Analog Devices. External sockets are provided for the optional, external, CONVST and CLKIN inputs and the VIN1-VIN4 inputs.
Fig. 1: FUNCTIONAL BLOCK DIAGRAM
Conversion Sequence Selection Links
External Power Supplies Input Buffers Vin1 Vin2 Vin3 RC Filter Vin4 RC Filter External Reference RC Filter
Data Bus RC Filter
Input Range Selection Links
AD7864 ADC
Control lines
96 Pin DIN Connector
REV. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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