Linear Technology DC547A Demo Manual

Description
Demonstration circuit 547A features the
150ksps analog-to-digital converter.
This board provides a means to evaluate the performance of
the LTC1864L 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 547A is easy to set up to evaluate
the performance of the LTC1864L. 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 64× the sample
rate. Figure 1 shows the default jumper positions.
1. Connect the parallel output Pins 1-40 to either the
DC718 data collection board, or to a suitable acquisition
system. Pin 3 is the data strobe.
DEMO MANUAL DC547A
LTC1864L 16-bit is hence much greater than what would be required in
almost any practical application.
The LTC1864L and its demo board are intended to be
used with the PScope data acquisition system for char-
acterization of the ADC in AC applications extending from
DC to 1.5MHz. The full power bandwidth of the LTC1864L
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
applications, but it is not necessarily the best for all ap-
plications.
The board also incorporates an LTC1799 resistor pro-
grammable oscillator as an optional clock source.
Design files for this circuit board are available at
http://www.linear.com/demo/DC547A
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.
2. Observe correct polarity; Connect +8V to +15V to the
+15V terminal. Note that –15V is only required if U2 is
installed. There are two on board regulators. U1, the
reference voltage is 2.5V. U11 at 3.3V, provides power
to the board. If the intent is to do an evaluation of AC
performance, connect a sinusoidal (or other) input
signal to J1, or J1 and J2. If only J1 is used (single-
ended operation), JP3 should be connected to GND.
This converter converts unipolar differential inputs from
0 – V
16-Bit, 150ksps, 3V ADC
.
REF
LTC1864L
dc547af
1