Linear Technology DC416 Demo Manual

Description
Demonstration circuit 416 features the
250ksps analog-to-digital converter.
This board provides a means to evaluate the performance
of the LTC1864 with either the Linear Technology PScope™
data acquisition system, or with other parallel or serial
data acquisition systems.
The board also demonstrates proper layout techniques in
the circuitry surrounding the ADC and in the segmenta-
tion of the planes required to achieve full performance
with the ADC.
These techniques include proper grounding of the device
and associated bypass capacitors, placement of the device
relative to interconnection of analog and digital subsystems
and signal routing in proximity to the ADC.
This board performs serial to parallel conversion in a man-
ner that is unlikely to be used in an actual implementation,
but is representative of what could be implemented in an
FPGA. It is expected that with this ADC, the interface will
be performed serially with either programmable logic, a
general-purpose processor, a DSP, or across an isolated
link of one of many types. The complexity of the circuitry
quick start proceDure
Demonstration circuit 416 is easy to set up to evaluate
the performance of the LTC1864. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
NOTE: The demo board is shipped with jumpers in place
to allow the use of an external oscillator at 80× the sample
rate. Figure 1 shows the default jumper positions.
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LTC1864 16-bit is hence much greater than what would be required in
almost any practical application.
The LTC1864 and its demo board are intended to be used
with the PScope data acquisition system for characteriza-
tion of the ADC in AC applications extending from Hz to
MHz. The full power bandwidth of the LTC1864 is high
enough to produce good performance in under-sampling
applications, as well as applications where the signal
content is below Nyquist.
The board contains a bandwidth-limiting filter at the input
of the ADC (C7, C8, C9, R1 and R2), as well as provision
for an amplifier (U2). This bandwidth-limiting filter (–3dB at
1.5MHz) is typical of what may be required for many applica-
tions, but it is not necessarily the best for all applications.
The board also incorporates an LTC1799 resistor program-
mable oscillator as an optional clock source.
Design files for this circuit board are available at
http://www.linear.com/demo/DC416
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and PScope
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
1. Connect the parallel output J4 to either the DC718 data
collection board, or to a suitable acquisition system.
Pin 3 of J4 is the data strobe.
2. Observe correct polarity; Connect +8V to +15V to
terminal E1. Note that –15V is only required if U2 is
installed. There are two on board regulators. Both are
5V, although U1 the reference can be substituted with
a lower voltage.
DEMO MANUAL DC416
16-Bit 250ksps ADC
LTC1864
dc416f
1