EVAL-AD7685CB Analog Devices Inc, EVAL-AD7685CB Datasheet - Page 3

• Manufacturer Part Number: EVAL-AD7685CB
• Description: BOARD EVAL FOR AD7685
• Manufacturer: Analog Devices Inc
• Series: PulSAR®r

Specifications of EVAL-AD7685CB

• Number Of Adc's: 1
• Number Of Bits: 16
• Sampling Rate (per Second): 250k
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Input Range: ±VREF
• Power (typ) @ Conditions: 10mW @ 250kSPS
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD7685
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Preliminary Technical Data
DETAILED Description
The EVAL-AD768x/AD769x/AD794xCB includes a 5 V
ultrahigh precision reference (ADR435), and a signal
conditioning circuit with two opamps (ADA4841) and digital
logic. The board interfaces with a 96-way connector for the
EVAL-CONTROL BRDx and a 26-pin IDC connector for the
serial output interface.
The EVAL-AD768x/AD769x/AD794xCB is a four-layer board
carefully laid out and tested to demonstrate the specific high
accuracy performance of the AD768x/AD769x/AD794x.
Figure 2 through Figure 5 show the schematics of the evaluation
board. The layouts of the board are shown in the following
figures:
Figure 6: Top-Side Silk-Screen
Figure 7: Top-Side Layer
Figure 8: Ground Layer
Figure 9: Shield Layer
Figure 10: Bottom-Side Layer
Figure 11: Bottom-Side Silk-Screen
The EVAL-AD768x/AD769x/AD794xCB has a flexible design
that enables the user to choose among many different board
configurations. A description of each selectable jumper is listed
in Table 1, and the available test points are listed in Table 2.
The EVAL-AD768x/AD769x/AD794xCB is configured in the
factory with the front-end amplifiers U6 and U7 set to a gain
of 1. The board is set to be powered through the EVAL-
CONTROL BRDx.
Buffered conversion data is available at the output parallel bus
BD on U3 and on the 96-pin connector P3 and is valid during
the falling edge of BBUSY on P3. Activity of the ADC turns on
the on-board LED
Power Supplies and Grounding
The EVAL-AD768x/AD769x/AD794xCB has two power supply
blocks:
-SJ2 for the analog section including the AD768x/
AD769x/AD794x, the signal conditioning and the reference
voltage circuitry.
-SJ1 for the digital interface circuitry and the digital section of
the ADC.
These offer flexibility to evaluate the ADC and the surrounding
circuitry with any power supply combination.
Analog Input Ranges and Multiplexing
The analog front-end amplifier circuitry U6 and U7 allows
flexible configuration changes such as positive or negative gain,
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input range scaling, filtering, addition of a DC component, use
of different op-amp and supplies.
The factory configuration of the analog input of U6 and U7 is
set at midscale. This allows a transition noise test without any
other equipment. An FFT test can be done by applying a very
low distortion AC source.
As an option, an
the ADC to demonstrate performances for multichannel
applications.
A second ADC can be mounted on the board to demonstrate
the daisy-chain feature.
Using the EVAL-AD768x/AD769x/AD794xCB
Software
This configuration requires to use the EVAL-CONTROL BRDx
to interface the EVAL-AD768x/AD769x/AD794xCB with the
PC.
Software Description
The EVAL-AD768x/AD769x/AD794xCB comes with software
for analyzing the AD768x/AD769x/AD794x. One can perform a
histogram to determine code transition noise, and Fast Fourier
Transforms (FFT's) to determine the Signal-to-Noise Ratio
(SNR), Signal-to-Noise-plus-Distortion (SINAD) and Total-
Harmonic-Distortion (THD). The AC performances can also
been evaluated after digital filtering (averaging) with enhanced
resolution (up to 32 bits). The front-end PC software has four
screens:
Figure 12 is the Setup Screen where sample rate, number of
samples are selected.
Figure 13 is the Histogram Screen, which allows the code
distribution for DC input and computes the mean and standard
deviation.
Figure 14 is the FFT Screen, which performs an FFT on the
captured data, computes SNR, SINAD and THD.
Figure 15 is the time domain representation of the output.
When the on-board conversion (CNV) generation is used, a
synchronous FFT can be achieved by synchronizing an external
AC generator with the 10MHz Fsync signal (J4) a 10 MHz
signal, exact division of master clock (MCLK).
Figure 16 is the FFT Screen when averaging is used.
Software Installation (executable)
There is no need to have LabVIEW installed to run the
executable.
Double-click on Setup.exe in the LabVIEW exe folder from the
CD-ROM shipped with EVAL-AD768x/AD769x/AD794xCB
(do not use the CD shipped with the EVAL-CONTROL BRDx)
EVAL-AD768x/AD769x/AD794xCB
ADG739
multiplexer can be used in front of