AD9040A Analog Devices, Inc., AD9040A Datasheet - Page 8

• Manufacturer Part Number: AD9040A
• Description: 10-bit 40 Msps A/d Converter
• Manufacturer: Analog Devices, Inc.

AD9040A
Layout Information
Preserving the accuracy and dynamic performance of the
AD9040A requires that designers pay special attention to the
layout of the printed circuit board.
Analog paths should be kept as short as possible and be properly
terminated to avoid reflections. The analog input and reference
voltage connections should be kept away from digital signal
paths; this reduces the amount of digital switching noise which
is capacitively coupled into the analog section. Digital signal
paths should also be kept short, and run lengths should be
matched to avoid propagation delay mismatch. The AD9040A
digital outputs should be buffered or latched close to the device
(<2 cm). This prevents load transients which may feedback into
the device.
In high speed circuits, layout of the ground is critical. A single,
low impedance ground plane on the component side of the
board is recommended. Power supplies should be capacitively
coupled to the ground plane with high quality chip capacitors to
reduce noise in the circuit. Multilayer boards allow designers to
lay out signal traces without interrupting the ground plane, and
provide low impedance ground planes. In systems with dedi-
cated analog and digital grounds, all grounds of the AD9040A
should be connected to the analog ground plane.
The power supplies of the AD9040A should be isolated from
the supplies used for external devices; this reduces the amount
of noise coupled into the ADC. The digital +5 volt connection
of the device (V
be connected to the same supply as +V
necting V
device. Sockets limit dynamic performance and are not recom-
mended for use with the AD9040A.
EVALUATION BOARD
The evaluation board for the AD9040A (AD9040A/PCB) pro-
vides an easy and flexible method for evaluating the ADC’s
D
to a system digital supply may couple noise into the
D
, Pin 23) powers the digital outputs and should
S
(Pins 3 and 10). Con-
–8–
performance without (or prior to) developing a user-specific
printed circuit board. The two-sided board includes a recon-
struction DAC and digital output interface, and uses the layout
and applications suggestions outlined above. It is available from
Analog Devices at nominal cost.
Generous space is provided near the analog input and digital
outputs to support additional signal processing components the
user may wish to add. This prototyping area includes through
holes with 100-mil centers to support a variety of component
additions.
Input/Output/Supply Information
Power supply, analog input, clock connections, and recon-
structed output (RC OUTPUT) are identified by labels on the
evaluation board. Operation of the evaluation board should
conform to the following characteristics:
Parameter
Supply Current
A
CLOCK
RC OUTPUT
Analog Input
Analog input signals can be fed directly into the Device Under
Test input (A
a 51
IN
+5 V
–5.2 V
Impedance
Voltage Range
Impedance
Frequency
Impedance
Voltage Range
resistor.
Table I. Evaluation Board Characteristics
IN
). The A
IN
input is terminated at the device with
Typical
250
300
51
51
40
51
0 V to –1 V
1.0
Units
mA
mA
V
MSPS
V
REV. B