DC854C - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT 130 MSPS ADC
LTC2208, LTC2208-14
DESCRIPTION
Demonstration circuit 854 supports a family of
16/14-Bit 130Msps ADCs. Each assembly features
one of the following devices: LTC2208, LTC220814 high speed, high dynamic range ADCs.
This Demonstration circuit only supports CMOS
output operation. For demonstration of LVDS output signaling, please see DC996.
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. Refer to
the datasheet for applications information.
Design files for this circuit board are available.
Call the LTC factory.
LTC is a trademark of Linear Technology Corporation
1. DC854 Variants
DC854 VARIANTS
ADC PART NUMBER
RESOLUTION*
MAXIMUM SAMPLE 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
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 MSPS ADC
2. Performance Summary (TA = 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
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 MSPS ADC
1)
DC854 Setup (zoom for detail)
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 MSPS ADC
POWER
ANALOG INPUT NETWORK
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.
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.
The DC718 data collection board is normally 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 input. It is
terminated with 50 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
be large, up to 3VP-P or +13dBm. Using bandpass
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
are capacitive coupled to Balun transformers ETC11-13, or directly coupled through Flux coupled
transformers ETC1-1T. (See Schematic)
In almost all cases, filters will be required on both
analog input and encode clock to provide data sheet
SNR.
DC854D 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 in the schematic.
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 output is available on Pins 7-37 for 16-Bits (or 7-33 for 14-Bits)
of J1 which can be collected via a logic analyzer,
cabled to a development system through a SHORT
2 to 4 inch long 40-pin ribbon cable or collected by
the DC718 QuickEval-II Data Acquisition Board.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT 130 MSPS ADC
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 device,
LTC2208, through LTC2208-14. Select the part in
the Device List and PScope 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 LTC2208 in
the device menu, you may manually configure as:
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 MSPS ADC
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 854
16/14 BIT 130 MSPS ADC
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