DEMO MANUAL DC2303
LTC2000, LTC2000A
16-, 14-, 11-Bit, 2.5Gsps to 2.7Gsps DACs
Description
Demonstration circuit 2303 supports the
LTC
®
2000
and
LTC2000A,
a high speed, high dynamic range family of
DACs. It was specially designed for applications that re-
quire differential DC coupled outputs. DC2303 supports
the complete family of the LTC2000 including 16-, 14- and
11-bit parts. For all the variations see Table 1.
The DC2303 was designed to conform to the FMC form
factor allowing this board to be used with standard FMC
FPGA demo boards and mounted into FMC chassis.
Table 1. DC2303 Variants
DC2303 VARIANTS
DC2303A-A
DC2303A-B
DC2303A-C
DC2303A-D
DC2303A-E
DC2303A-F
PART NUMBER
LTC2000-16
LTC2000-14
LTC2000-11
LTC2000A-16
LTC2000A-14
LTC2000A-11
RESOLUTION
16-Bit
14-Bit
11-Bit
16-Bit
14-Bit
11-Bit
MAXIMUM SAMPLE RATE
2.5Gsps
2.5Gsps
2.5Gsps
2.7Gsps
2.7Gsps
2.7Gsps
OUTPUT FREQUENCY
DC-1000MHz
DC-1000MHz
DC-1000MHz
DC-1080MHz
DC-1080MHz
DC-1080MHz
The circuitry on the analog outputs is optimized for analog
frequencies from DC-1.08GHz.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2303
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
performance summary
PARAMETER
Supply Voltage – DC2303
Sampling Frequency (Sample Clock Frequency)
Sample Clock Level (Single-Ended)
LVDS Inputs
Specifications are at T
A
= 25°C
MIN
4.8
300
0
±0.2
0.4
TYP
5.0
MAX
5.2
2500 or 2700
15
±0.6
1.8
UNITS
V
MHz
dBm
V
V
CONDITIONS
This supply must provide up to 800mA
Use a 50Ω Source
Differential Input Voltage Range
Common Mode Voltage Range
dc2303f
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DEMO MANUAL DC2303
Quick start proceDure
DC2303 is easy to set up to evaluate the performance of the
LTC2000. Refer to Figure 1 for proper measurement equip-
ment setup and follow the procedure below.
Setup
The Xilinx KC705 development kit and a DC2159 was
supplied with the DC2303 demonstration circuit. If these
boards were not provided, follow the KC705 demo manual
to install the required software and for connecting the
KC705 board to the DC2303 and DC2159 and to a PC.
SINGLE ENDED
SAMPLE CLOCK INPUT
DIFFERENTIAL OUTPUTS.
NOMINAL OUTPUTS LOOK
LIKE 50 PER SIDE TO
DRIVE AN EXTERNAL
BALUN, OR COMBINER.
+
5V
JUMPERS SHOWN IN THEIR DEFAULT POSITIONS. THE
DC2303 CONNECTS TO THE XILINX KC705 BOARD VIA
FMC CONNECTORS
Figure 1. DC2303 Setup (Zoom for Details)
dc2303f
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DEMO MANUAL DC2303
Quick start proceDure
HARDwARE SETUP
SMAs
J4:
Sample Clock Input. Apply a clock signal to this
SMA connector from a 50Ω driver. A 0dBm clock source
should be sufficient, but for best phase noise and jitter
performance, use the highest possible amplitude and slew
rate, up to 15dBm.
J1, J3:
Differential Output Signals. These SMAs provide
access to the differential outputs of the DAC. The output
impedance is designed to be 50Ω at each SMA, or 100Ω
differential. Connect an external balun or combiner to
these pins to drive a single-ended spectrum analyzer.
Linear Technology has various adaptor boards for specific
frequencies and applications. More information is available
at
www.linear.com/LTC2000#demoboards.
J2:
SYNCH. This SMA is to provide access to the sync pin
of the LT8614. It is not used in normal use.
Turrets
5V (E4):
Positive Input Voltage for the DAC and Digital Cir-
cuits. This voltage feeds a series of regulators that supply
the proper voltages for the DAC. The voltage range for this
turret is 4.8V to 5.2V. Note: For close-in phase noise plots,
driving this voltage is not ideal. There is a known 20kHz noise
hump in the spectrum that is generated by the regulators. For
the best phase noise performance, back drive the onboard
regulators with the provided turrets from a low noise supply.
GND (E1):
Ground Connection. This demo board has only
a single ground plane. This turret should be tied to the
GND terminal of the power supply being used.
FSADJ (E8):
This is an optional pin that is tied directly
to the FSADJ pin of the DAC. It can be used to set the
full-scale output current of the DAC. In normal operation
this pin is tied to GND through 500Ω to set a current of
40mA at the output. See data sheet for equations to set
different current levels, then replace R45 on the backside
of the board.
REFIO (E2):
This pin is tied directly to the REFIO pin of the
DAC and is used to set the reference voltage for the DAC.
Normally it is internally set to 1.25V but can be overdriven
with an external voltage from 1.1V to 1.4V.
TEST POINTS
AVDD1V8 (E5):
Optional 1.8V Input. This pin is connected
directly to the AVDD18 pin of the DAC. It requires a supply
that can deliver up to 1A. Driving this pin will override the
onboard regulator.
DVDD3V3 (E3):
Optional 3.3V Input. This pin is connected
directly to the DVDD33, AVDD33 and SVDD pins of the
DAC. It requires a supply that can deliver up to 50mA.
Driving this pin will override the onboard regulator.
DVDD1V8 (E6):
Optional 1.8V Input. This pin is connected
directly to the DVDD18 pin of the DAC. It requires a supply
that can deliver up to 500mA. Driving this pin will override
the onboard regulator.
VP1 (E7):
This is a test point that is at the output of the
onboard switching regulator. It is meant for test purposes.
It can also be driven to 2.5V to shut down the output of
the switching regulator.
TSTP, TSTN:
These pins are tied directly to the TSTP and
TSTN pins of the DAC. They can be used to measure the
internal temperature and timing of the LVDS inputs.
CS:
Chip Select. This pin connects directly to the
CS
pin
of the LTC2000.
SCK:
Serial Clock. This pin connects directly to the SCK
pin of the LTC2000.
SDI:
Serial Data Input. This pin connects directly to the
SDI pin of the LTC2000.
SDO:
Serial Data Output. This pin connects directly to the
SDO pin of the LTC2000.
dc2303f
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DEMO MANUAL DC2303
Quick start proceDure
Jumpers
The DC2303 demonstration circuit should have the fol-
lowing jumper settings as default positions.
JP1:
In the RUN position this pin results in normal opera-
tion of the DAC. In the SHDN position the DAC is powered
down. (Default: RUN or up)
JP2:
EEPROM Write Protect. For factory use only. Should
be left in the protected (WP) position.
Connectors
P1:
FMC Connector. This connector is designed to connect
to the Xilinx KC705 board or any other FMC compatible
FPGA board. All of the communication between the FPGA
and the DAC is routed through this connector.
APPLYING POwER AND SIGNALS TO THE DC2303
DEMONSTRATION CIRCUIT
If a KC705 demo board is used to supply data to the
DC2303, the two boards should first be bolted together
for a proper electrical connection.
If Linear Technology provided the KC705 board the proper
FPGA programming file (bit file) is already installed in
flash memory and will begin to operate when the board
is powered on. A DC2159 was also provided for a USB
connection between the LTDACGen software and the FPGA.
If an unprogrammed FPGA board is used, refer to the ap-
propriate documentation on how to program it.
Power should be applied to the system in this order:
1. Connect the DC2303 to the KC705 board on HPC FMC
connector, J22. Connect the DC2159 demo board into
the LPC FMC connector, J2.
2. Connect the USB cable to J3 of the provided DC2159.
3. Apply a clock to J4 of the DC2303.
4. Connect any optional output board, like the DC2266,
to J1 and J3.
5. Connect the 5V from a bench supply to the 5V turret
on the DC2303.
dc2303f
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DEMO MANUAL DC2303
Quick start proceDure
6. Turn on the voltage to the KC705.
7. Open the LTDACGen software and hit connect.
LTDACGen should report back that it is connected to the
FPGA. See Figure 2.
ANALOG OUTPUT NETwORK
The analog output network of the DC2303 has been
designed to maximize the performance of the LTC2000.
The LTC2000 drives two 50Ω resistors on each side to
minimize the impedance it sees. This maximizes the SFDR
the DAC is able to produce. If a larger signal swing is
required this impedance can be increased, but the SFDR
might degrade. The output also has a pi network of 50Ω
resistors to pad the output impedance of the board up to
50Ω per side. This allows the demo board to drive a 50Ω
analyzer through a balun or other combiner.
Linear Technology has various adaptor boards for specific
frequencies and applications. More information is available
at
http://www.linear.com/product/ LTC2000#demoboards.
SAMPLE CLOCK
The sample clock to the DC2303 demonstration circuit
board is marked J4. As a default it is a single-ended 50Ω
input port. There is an onboard balun that does a single-
ended to differential translation.
For the best noise performance, the sample input must
be driven with a very low jitter signal generator source.
The amplitude should be as large as possible up to ±3.6V
or 15dBm.
Figure 2. LTDACGen Connected to FPGA
dc2303f
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