QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 918
16/14 BIT 40 TO 105 MSPS ADC
4
APPLYING POWER AND SIGNALS TO THE DC918
DEMONSTRATION CIRCUIT
If a DC718 is used to acquire data from the DC918,
the DC718 must FIRST be connected to a powered
USB port or provided an external 6-9V BEFORE ap-
plying +3.3V across the pins marked “+3.3V” and
“PWR GND” on the DC918. The DC918 demonstra-
tion circuit requires up to 500mA depending on the
sampling rate and the A/D converter supplied.
The DC718 data collection board is powered by the
USB cable and does not require an external power
supply unless it must be connected to the PC
through an un-powered hub in which case it must
be supplied an external 6-9V on turrets G7(+) and
G1(-) or the adjacent 2.1mm power jack.
ENCODE CLOCK
NOTE: This is not a logic compatible input. It is
terminated with 50 Ohms. Apply an encode clock
to the SMA connector on the DC918 demonstration
circuit board marked “J3 ENCODE INPUT”.
For the best noise performance, the ENCODE INPUT
must be driven with a very low jitter source. When
using a sinusoidal generator, the amplitude should
be large, up to 3V
P-P
or 13dBm. Using band pass
filters on the clock and the analog input will im-
prove the noise performance by reducing the wide-
band noise power of the signals. Datasheet FFT
plots are taken with 10 pole LC filters made by TTE
(Los Angeles, CA) to suppress signal generator
harmonics, non-harmonically related spurs and
broad band noise. Low phase noise Agilent 8644B
generators are used with TTE band pass filters for
both the Clock input and the Analog input.
Apply the analog input signal of interest to the SMA
connectors on the DC918 demonstration circuit
board marked “J2 ANALOG INPUT”. These inputs
are capacitive coupled to Balun transformers ETC1-
1-13, or directly coupled through Flux coupled
transformers ETC1-1T.
An internally generated conversion clock output is
available on pin 3 of J1 and the data samples are
available on Pins 7-37 for 16-Bits (or 7-33 for 14-
Bits) of J1 which can be collected via a logic ana-
lyzer, cabled to a development system through a
SHORT 2 to 4 inch long 40-pin ribbon cable or col-
lected by the DC718 QuickEval-II Data Acquisition
Board using the
PScope System Software
provided
or down loaded from the Linear Technology website
at http://www.linear.com/software/. If a DC718 was
provided, follow the DC718 Quick Start Guide and
the instructions 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.
If the DC918 demonstration circuit is properly con-
nected to the DC718, PSCOPE should automatically
detect the DC918, and configure itself accordingly.
If necessary the procedure below explains how to
manually configure PSCOPE.
Configure PScope for the appropriate variant of the
DC918 demonstration circuit by selecting the cor-
rect A/D Converter as installed on the DC918. Un-
der the “Configure” menu, go to “Device.” Under
the “Device” pull down menu, select device, either
LTC2207, LTC2207-14, LTC2206, LTC2206-14,
LTC2205, LTC2205-14, or LTC2204. Select the part
in the Device List and PScope will automatically
blank the last two LSBs when using a DC918 sup-
plied with a 14-Bit part. You may also manually
configure Pscope as follows:
User configure
16-Bit (or 14-Bit if using -14 versions)
Alignment: Left-16
Bipolar (2’s complement)
