EVAL-AD7798EB Datasheet, PDF (1/7 Pages) Analog Devices – 16-Bit Low Power Σ-Δ ADC (3 Channels)

Preliminary Technical Data
Evaluation Board for the AD7798,
16-Bit Low Power Σ−∆ ADC (3 Channels)
EVAL-AD7798EB
FEATURES
Full-Featured Evaluation Board for the AD7798
Stand alone USB Interface
Various Linking Options
PC Software for Control of AD7798
INTRODUCTION
This Technical Note describes the evaluation board for the
AD7798 which is a Low Power, 16-Bit Sigma Delta ADC. The
AD7798 is a complete analog front end for low frequency
measurement applications. It contains three differential inputs
and includes a low noise instrumentation amplifier, reference
detect and a low side power switch. The update rate can be
varied from 4.17 Hz to 500 Hz. It also has an on-board clock,
eliminating the need for an external clock. It employs a sigma-
delta conversion technique to realize up to 16 bits of no missing
codes performance. The input signal is applied to an analog
modulator. The modulator output is processed by an on-chip
digital filter. The analog input channel of the AD7798 accepts
analog input signals of +VREF/Gain, with Gain equal to 1 to 128.
With a gain of 64 and the update rate programmed to 16.7 Hz,
the rms noise is 65 nV. Simultaneous 50 Hz/ 60 Hz rejection is
available at this data update rate also.
Full data on the AD7798 is available in the AD7798 datasheet
available from Analog Devices and should be consulted in
conjunction with this Technical Note when using the evaluation
board.
The evaluation board interfaces to the USB port of an IBM
compatible PC. Software is available with the evaluation board
which allows the user to easily communicate with the AD7798.
N.B.!! The AD7798 Evaluation Board Software should be
installed BEFORE connecting the AD7798 Evaluation board
to the PC.
Other components on the AD7798 Evaluation Board include
the ADP3303 which is a high precision, low power, 3.3V output,
voltage regulator, which is used to power the USB/SPI interface .
OPERATING THE AD7798 EVALUATION BOARD
Power Supplies
The board is powered via the 5V supply from the USB
connector, J1. This 5V supply may be used to power the
AD7798 directly or a 3.3V Regulated voltage from the on board
ADP3303, high precision, low power, 3.3V output, voltage
regulator may also be used. Alternatively, the AD7798 may be
powered using an external 3V or 5V power supply via J3.
FUNCTIONAL BLOCK DIAGRAM
AVDD
TEMPERATURE
SENSOR
VOLTAGE
REGULATOR
ANALOG
INPUTS
AD7798
SPI / USB
INTERFACE
PC
+
LABVIEW
BASED
SOFTWARE
VOLTAGE
REF
REFIN
Figure 1. Functional Block Diagram
Rev. Pr A
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