CDB5471 Datasheet, PDF (4/26 Pages) Cirrus Logic – Evaluation Board and Software

CDB5471
1. INTRODUCTION
The CDB5471 Evaluation Board demonstrates the
performance of the CS5471 6-channel A/D con-
verter.
The CDB5471 evaluation board provides a quick
means of evaluating the CS5471. Analysis soft-
ware supplied with the CDB5471 allows the user to
observe the CS5471’s digital output data on the us-
er’s PC monitor. The PC software allows the user
to quantify the device’s performance in the time-
domain and frequency domain. The user can save
raw data from the CS5471 to a data file, which al-
lows to user to analyze performance with other
tools that may be preferable to the user.
1.1 CS5471
The CS5471 is a highly integrated Two-Channel
Delta-Sigma Analog-to-Digital Converter (ADC)
developed for power measurement/metering appli-
cations. However the CS5471 has other potential
uses in various data acquisition applications, par-
ticularly in motor/servo control applications which
require very high precision. The CS5471 combines
two delta-sigma modulators with decimation fil-
ters, along with a master-mode serial interface on a
single chip device. The CS5471 was designed for
the purpose of performing the A/D conversion op-
erations required at the front-end of a digital single-
phase metering system. The six ADC channels can
be thought of as a pair of voltage/current-channel
ADC’s in a digital single-phase power metering ap-
plication.
The CS5471 contains one programmable gain am-
plifier (PGA) for the current input. The PGA sets
the maximum input level of the current channel at
±800 mV DC (for gain = 1x) or ±40 mV DC (for
gain = 20x). The voltage channel has only the 1x
gain setting, and so the range of input levels on the
voltage channel is ±800 mV DC.
Additional features of CS5471 include a charge
pump driver, on-chip 1.2 V reference, and a digital
input that can select between two different output
word rates. (The two output word rates are equal to
XIN/2048 and XIN/1024.)
The CS5471 requires a 1.2 V reference input on
VREFIN. The ∆Σ modulators and high rate digital
filters allow the user to measure instantaneous volt-
age and current at an output word rate of 4 kHz (or
2000 kHz, depending on the state of the OWRS
pin) when a 4.096 MHz clock source is used.
1.2 Data Flow on Evaluation Board
The output serial bit-stream from the CS5471 is
shifted into an 8-bit latch circuit so that it can be
quickly ported to the DB25 connector. From this
connector, the data can be sent through the provid-
ed 25-pin printer cable to the parallel port of the us-
er’s IBM-compatible PC (the PC must run under
Windows ‘95/’98/2000 operating system).
Once the 8-bit segments of data are ported to the
user’s PC, the LabWindows software (included
with this kit) will re-segment the data into the ap-
propriate 16-bit word format for both of the
CS5471’s two data channels. The data is sent
quickly to the user’s PC, which allows the software
to perform various data processing and graphical il-
lustrations on the digital output data. This includes
real-time RMS, variance, and standard deviation
calculations for both channels. The output data
from each channel can be plotted on-screen in the
time domain or in the frequency domain. A histo-
gram function is also included to help the user to
evaluate the noise characteristics of each channel.
The software can also calculate the mean and stan-
dard deviation of the output codes both channels.
This feature allows the user to scrutinize the varia-
tion of the A/D converters if the user applies con-
stant DC voltage levels to the inputs. RMS
calculation is also provided to assist in the quick
analysis AC input signals.
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DS480DB1