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4.5 Power Requirements
The
power
supply
ADC081500 Evaluation Board is 12V at 800mA.
Most of the regulators on board are switching
regulators for increased power efficiency.
The board typically draws around 500mA but it
is always good practice to have extra power
reserve in the power supply over the typical
power requirements.
A Universal 100-240V AC input to 12V DC Brick
Power Supply is included with the development
board.
4.6 Power Supply Connections
Power to this board is supplied through the
power connector on the rear panel. It is advised
that only the supplied PSU is used with this
board.
The ADC081500 supply voltage has been set to
1.9V, ±50 mV.
5.0 Obtaining Best Results
Obtaining the best results with any ADC
requires both good circuit techniques and a
good PC board layout. For layout information for
this product please contact you nearest National
Semiconductor representative
5.1 Clock Jitter
When any circuitry is added after a signal
source, some jitter is almost always added to
that signal. Jitter in a clock signal, depending
upon how bad it is, can degrade dynamic
performance. We can see the effects of jitter in
the frequency domain (FFT) as "leakage" or
"spreading" around the input frequency, as seen
in Figure 2a. Compare this with the more
desirable plot of Figure 2b. Note that all dynamic
performance parameters (shown to the right of
the FFT) are improved by eliminating clock jitter.
requirement
for
the
.
Figure 2a. Jitter causes a spreading around the input
signal, as well as undesirable signal spurs.
Figure 2b. Eliminating or minimizing clock jitter results in
a more desirable FFT that is more representative of how
the ADC actually performs.
6.0 Evaluation Board
Specifications
Power Requirements: +12V, 800mA
Clock Frequency Range : 200 MHz to 1.5 GHz
Analog Input Range (AC Coupled) 30MHz to 1800MHz
Nominal Analog Input Voltage: 560 mV P-P to 870 mV P-P
5
Board Size: 168mm x 100mm
Impedance: 50 Ohms
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