clc5958 National Semiconductor Corporation, clc5958 Datasheet - Page 10

• Manufacturer Part Number: clc5958
• Description: 14-bit, 52msps A/d Converter
• Manufacturer: National Semiconductor Corporation

http://www.national.com
Power Supplies
The V
circuitry with the exception of the digital output buffers.
The DV
Each supply pin should be connected to a supply (i.e. do
not leave any supply pins floating).
Local groups of supply pins should be bypassed
with.01uF capacitors. These capacitors should be placed
as close to the part as possible. Avoid using via to the
ground plane. If vias to the ground plane cannot be
avoided, then use multiple vias in close proximity to the
bypass capacitor.
The supplies should be bypassed in a manner to prevent
supply return currents from flowing near the analog
inputs. The evaluation board layout is an example of how
to accomplish this.
The digital output buffer supplies (DV
means for programming the output buffer high level.
Supply values ranging from 3.3V to 5.0V may be applied
to these pins. In general, best performance is achieved
with DV
Description
The CLC5958 evaluation printed circuit board provides a
convenient test bed for rapid evaluation of the CLC5958.
It illustrates the proper approach to layout in order to
achieve best performance, and provides a performance
benchmark.
Analog Input
The CLC5958 evaluation board is configured to be driven
by a single-ended signal at the AIN SMA connector (the
AIN connector is disconnected). The AIN SMA
connector should
impedance. A full scale input is approximately 1.4V
(7dBm). The single-ended input is converted to a
differential input by an on-board transformer.
When performing sine wave testing, it is critical that the
input sine wave be filtered to remove harmonics and
source noise.
Encode Input
The CLK SMA connector is the encode input and should
also be driven from a 50 source. A low jitter 16dBm sine
wave should be applied at this input. In some cases it
may be necessary to band-pass filter the sine wave in
order to achieve low jitter.
CC
CC
CC
pins provide power to the digital output buffers.
pins supply power to all of the CLC5958
set to 3.3V.
be
driven
from
CLC5958 Evaluation Board
a
CC
50
) provide a
source
10
pp
Layout Recommendations for the CSP
The 48 lead chip scale package not only provides a small
footprint, but also provides an excellent connection to
ground. The thermal vias on the bottom of the package
also serve as additional ground pads. The solder pad
dimensions on the pc board should match the package
pads 1:1.
Soldering Recommendations for the CSP
A 4 mil thick stencil for the solder screen printing is
recommended. The suggested IR reflow profile is:
The single-ended clock input is converted to a differential
signal by an on-board transformer and buffered by an
ECL buffer.
Digital Outputs
The digital outputs are available at the Eurocard
connector (J1). Data bits D0 through D13 are available at
J1 pins 18B through 5B. The data ready signal (labeled
DR in the schematic) is available at J1 pin 20B. These
outputs are also available at the HP 01650-63203
termination adapter for direct connection to an HP logic
analyzer (see evaluation board schematic). The outputs
are buffered by 3.3V digital latches. The falling edge of
the data ready signal may be used to latch the output data.
Supply Voltages
Power is sourced to the board through the Eurocard con-
nector. A 5V supply should be connected at J1 pins 32A
and 32B. A 3.3V supply should be connected at J1 pins
31A and 31 B. The ground return for these supplies is at
J1 pins 27A, 27B, 28A, and 28B. It is recommended that
low noise linear supplies be used.
Ramp Up:
Dwell Time > 183°C:
Solder Temperature:
(max solder temperature):
Dwell Time @ Max Temp:
Ramp Down:
2°C/sec
75 sec
215°C
235°C
5 sec
2°C/sec