DC854D - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
LTC2208, LTC2208-14, LTC2217, LTC2216, LTC2215
DESCRIPTION
Demonstration circuit 854 supports a family of
16/14-Bit 130Msps ADCs. Each assembly features
one of the following devices: LTC2208, LTC220814, LTC2217, LTC2216, LTC2215 high speed family
of high dynamic range ADCs.
This Demonstration circuit only supports CMOS
operation. For demonstration of LVDS output signaling, please see DC996.
Other members of this family include the LTC2207, a
105Msps 16-Bit CMOS-only version of this device, as
well as lower speed versions and single-ended clock
versions. These 7x7mm QFN devices are supported by
Demonstration circuits 918 and 919 (for single-ended
clock input).
1.
The versions of the DC854C and DC854D demo
board that support the LTC2208 16-Bit and
LTC2208-14 14-Bit series of A/D converters are
listed in Table 1. Depending on the required resolution, sample rate and input frequency, the DC854
is supplied with the appropriate ADC and with an
optimized input circuit. The circuitry on the analog
inputs is optimized for analog input frequencies below 70MHz or from 70MHz to 140MHz. For higher
input frequencies, contact the factory for support.
Design files for this circuit board are avail
available.
Call the LTC factory.
LTC is a trademark of Linear Technology Corporation
DC854 Variants
DC854 VARIANTS
VARIANT S
ADC PART NUMBER
RESOLUTION*
MAXIMUM SAM
SA MPLE RATE
INPUT FREQUENCY
854D-A
LTC2208
16-Bit
130Msps
1MHz - 70MHz
854D-B
LTC2208
16-Bit
130Msps
70MHz -140MHz
854D-C
LTC2208-14
14-Bit
130Msps
1MHz - 70MHz
854D-D
LTC2208-14
14-Bit
130Msps
70MHz -140MHz
854D-E
LTC2217
16-Bit
105Msps
1MHz - 70MHz
854D-F
LTC2217
16-Bit
105Msps
70MHz -140MHz
854D-G
LTC2216
16-Bit
80Msps
1MHz - 70MHz
854D-H
LTC2216
16-Bit
80Msps
70MHz -140MHz
854D-I
LTC2215
16-Bit
65Msps
1MHz - 70MHz
854D-J
LTC2215
16-Bit
65Msps
70MHz -140MHz
854C-P
LTC2208
16-Bit
130Msps
>140MHz
854C-Q
LTC2208-14
14-Bit
130Msps
>140MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
2.
Performance Sum
Su m mary (T A = 25°C)
PARAMETER
CONDITION
Supply Voltage
Depending on sampling rate and the A/D converter provided, Optimized for 3.3V
this supply must provide up to 500mA.
[3.15V 3.45V min/max]
Analog input range
Depending on PGA Pin Voltage
1.5VPP to 2.25VPP
Minimum Logic High
2.4V
Maximum Logic Low
0.8V
Logic Output Voltage
Minimum Logic High @ -1.6mA
2.3V (33Ω Series terminations)
(74VCX245 output buffer, Vcc = 2.5V)
Maximum Logic Low @ 1.6mA
0.7V (33Ω Series terminations)
Sampling Frequency (Convert Clock Frequency)
See Table 1
Convert Clock Level
50 Ω Source Impedance, AC coupled or ground referenced
(Convert Clock input is capacitor coupled on board and terminated with 50Ω.)
Logic Input Voltages
VALUE
Resolution
See Table 1
Input frequency range
See Table 1
SFDR
See Applicable Data Sheet
SNR
See Applicable Data Sheet
2VP-P 2.5VP-P Sine Wave
or Square wave
QUICK START PROCEDURE
PROCEDURE
Demonstration circuit 854 is easy to set up to evaluate the performance of most members of the
LTC2208 family of A/D converters. Refer to Figure 1
SETUP
If a DC718 QuickDAACS Data Analysis and Collection
System was supplied with the DC854 demonstration
circuit, follow the DC718 Quick Start Guide to install
for proper measurement equipment setup and follow
the procedure below:
the required software and for connecting the DC718 to
the DC854 and to a PC running Windows98, 2000 or
XP.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
1)
DC854 Setup (zoom for detail)
JUMPERS
JUMPERS
The DC854 demonstration circuit board
should have the following jumper settings as default: (as per figure 1)
JP1:
JP2:
JP3:
JP4:
JP5:
JP6:
Output clock polarity: GND
SENSE: VDD, (Internal reference)
PGA: GND 2.25V range
RAND: GND Not randomized
SHDN: GND Not Shutdown
DITH: GND No internal dithering
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
are capacitive coupled to Balun transformers ETC11-13, or directly coupled through Flux coupled
transformers ETC1-1T. (See Schematic)
POWER
If a DC718 is used to acquire data from the DC854,
the DC718 must FIRST be connected to a powered
USB port or provided an external 6-9V BEFORE applying +3.3V across the pins marked “+3.3V” and
“PWR GND” on the DC854. The DC854 demonstration 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 is connected to the PC through an
un-powered hub. In this case it must be supplied
with 6-9V on turrets G7 (+) and G1 (-) or the adjacent 2.1mm power jack.
ENCODE CLOCK
NOTE: This is not a logic compatible in
in put. It is
terminated
terminated with 50 Ohms.
Ohms Apply an encode clock
to the SMA connector on the DC854 demonstration
circuit board marked “J3 ENCODE INPUT”. The
transformer is terminated on the secondary side
with 100 ohms, and further terminated at the ADC
(at C11).
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
often be large, up to 3VP-P or 13dBm. Using band
pass filters on the clock and the analog input will
improve the noise performance by reducing the
wideband noise power of the signals. Data sheet
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 DC854 demonstration circuit
board marked “J2 ANALOG INPUT”. These inputs
ANALOG INPUT NETWORK
For optimal distortion and noise performance the
RC network on the analog inputs should be optimized for different analog input frequencies. Refer
to the provided schematics. These two input networks cover a broad bandwidth and are not optimized for operation at a specific input frequency.
For input frequencies less than 5MHz, or greater
than 150MHz, other input networks may be more
appropriate.
In almost all cases, filters will be required on both
analog input and encode clock to provide data sheet
SNR.
This Demo board has provision for additional components that may be used to implement a band
pass filter, or more optimal return loss in a given
frequency range. The default population is a simple
network as shown below.
In some cases, 3-10dB pads may be required to
obtain low distortion.
If your generator cannot deliver full scale signals
without distortion, you may benefit from a medium
power amplifier based on a Gallium Arsenide Gain
block prior to the final filter. This is particularly true
at higher frequencies where IC based operational
amplifiers may be unable to deliver the combination
of low noise figure and High IP3 point required. A
high order filter can be used prior to this final amplifier, and a relatively low Q filter used between the
amplifier and the demo circuit.
DIGITAL OUTPUTS
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 14Bits) of J1 which can be collected via a logic analyzer, cabled to a development system through a
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
SHORT 2 to 4 inch long 40-pin ribbon cable or collected by the DC718 QuickEval-II Data Acquisition
Board.
SOFTWARE
The DC718B board is configurable by 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 DC854 demonstration circuit is properly connected to the DC718, PSCOPE should automatically
detect the DC854, and configure itself accordingly.
If necessary the procedure below explains how to
manually configure PSCOPE.
Configure PScope for the appropriate variant of the
DC854 demonstration circuit by selecting the correct A/D Converter as installed on the DC854. Under the “Configure” menu, go to “Device.” Under
the “Device” pull down menu, select the appropriate
device. Selecting the part in the Device List will
automatically blank the last two LSBs when using a
DC854 supplied with a 14-Bit part. If you are operating with a version of PScope that does not include
the IC of interest it can be manually selected by using the device menu. PScope may be manually
configure by selecting the following options:
User configure
16-Bit (or 14-Bit if using LTC2208-14)
Alignment: Left-16
Bipolar (2’s complement)
Positive clock edge
Type: CMOS
If everything is hooked up properly, powered and a
suitable convert clock is present, clicking the “Collect” button should result in time and frequency
plots displayed in the PScope window. Additional
information and help for PScope is available in the
DC718 Quick Start Guide and in the online help
available within the PScope program itself.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT, 130,105, 80, 65 MSPS ADC
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