EVAL-AD7764_15 Datasheet, PDF (3/23 Pages) Analog Devices – Evaluation Board for AD7764/AD7765 using

Preliminary Technical Data
HARDWARE DESCRIPTION
POWER SUPPLIES
The EVAL-AD7764/5EDZ must be powered using a power supply
that applies a 7.5 V between the V+ and GND terminals of
Connector J2.
This 7.5 V supply is then regulated on board using ADP3330-
2.5 ADP3330-5 devices (U5 and U3) to provide the 2.5 V and 5 V
signals required by the AD7764/AD7765 device.
A filter path of the 2.5 V supply is used to power other digital
functionality on the EVAL-AD7764/AD7765EDZ excluding the
AD7764/AD7765 device. A separately filtered 5 V supply also
supplies the crystal oscillator on the EVAL-AD7764/AD7765EDZ.
The crystal oscillator is provided for customers that wish to use the
device in a stand-alone manner where they wish to provide and
acquire the digital signals going to and from the AD7764/5 device.
For this case, the user may apply the MCLK sourced from the
crystal oscillator. Note that in the default mode the AD7764/5
evaluation board is set up so that the EVAL-CED1Z board
provides the MCLK signal to the ADC as well as providing and
acquiring all other digital signals for the evaluation system.
DIFFERENTIAL INPUT
The differential input to the AD7764/AD7765 device is applied
through the connector marked J1. This is an XLR audio
standard connector. The differential inputs are routed through
the AD7764/AD7765 on-board differential amplifier using the
external circuit components as detailed in the schematic as shown
in this technical note and the AD7764/AD7765 data sheets.
REFERENCE CIRCUIT
The AD7764/5 evaluation board uses the low noise ADR444
(4.096V) reference to supply the ADC. See Gerber files on
EVAL-AD7764/AD7765EDZ
AD7764/5 product pages on www.analog.com for details on the
layout and configuration for this reference supply.
STANDALONE OPERATION
The EVAL-AD7764/AD7765EDZ can be used in a standalone
manner (that is, without using the EVAL-CED1Z). In this case,
however, the user must provide all the required interface com-
munications and be able to provide a means to acquire the output.
SMB footprints, allow for external MCLK, SYNC, RESET and
Decimation rate signals to be applied to the AD7764/65 device. All
other digital signals are accessible either from the 34-pin header
(J4) or from the marked test points on the evaluation board.
DECOUPLING AND LAYOUT RECOMMENDATIONS
The data sheets of the AD7764/AD7765 devices contain specific
information about the decoupling and layout recommendations
required to achieve the optimum specifications.
The EVAL-AD7764/AD7765EDZ adheres to these recom-
mendations and is designed as the blueprint for users of the
AD7764/Ad7765 devices.
The EVAL-AD7764/AD7765EDZ are 4-layer boards. One layer
is a dedicated ground plane. All supplies to devices on the
EVAL-AD7764/AD7765EDZ are decoupled to this ground
plane. In addition to the PCB’s top and bottom layers, there is
also a layer for routing power signals. All layers of the board are
detailed in the Evaluation Board Schematic and Artwork
section.
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