QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 851
10/12/14 BIT 10 TO 105 MSPS ADC
7
Note that relative aperture measurements require
removal of these networks, or the results will sim-
ply show the relative phase through the RC net-
work. The measure of relative phase further re-
quires a resistive power divider, and matched ca-
bles, or the results will be misleading. Any relative
phase measurements should be confirmed by re-
versing the signals to confirm that the relative delay
is not due to the external network.
If relative phase measurements produce results of
greater that a fractional psec, please consult the
factory for assistance.
Channel to Channel Crosstalk on this demo board is
better than -110 dB for input frequencies below 140
MHz.
DATA COLLECTION
The conversion clock output and the parallel data for
both ADC channels are available on J1. This connec-
tor is designed to mate with a Samtec model MEC8-
150-02-L-D-EM2 receptacle. It is recommended that
this receptacle be used if something other than a
DC890 board is used to collect data.
DC890 QuickEval-II Data Acquisition Board uses the
PScope System Software
provided or downloaded
from the Linear Technology website at
http://www.linear.com/software/. If a DC890 was
provided, follow the Quick Start Guide and the in-
structions below.
To start the data collection software if “
PScope.exe
”,
is installed (by default) in
\Program Files\LTC\PScope\, double click the PScope
Icon or bring up the run window under the start
menu and browse to the PScope directory and select
PScope.
Configure PScope for the appropriate variant of the
DC851 demonstration circuit by selecting the correct
A/D Converter as installed on the DC851. Under the
“Configure” menu, go to “Device.” Under the “De-
vice” pull down menu, select device, LTC2280
through LTC2299. When evaluating 12 BIT parts,
select the appropriate LTC22XX part in the Device
List and PScope will automatically blank the last two
LSBs when using a DC851 supplied with a 14 Bit
part.
If everything is hooked up properly, powered, and a
suitable convert clock is present, clicking the “Col-
lect” button should result in time and frequency
plots displayed in the PScope window. The two
channel mode in Pscope provides a page for each
channel, and a page showing the frequency domain
plots of both channels. An additional window called
“X-channel” displays relative phase and amplitude of
the two channels. This can be used to gauge cross-
talk, or validate relative aperture delay. Additional
information and help for
PScope
is available in the
DC890 Quick Start Guide and in the online help
available within the
PScope
program itself.
