AD9070/PCB Analog Devices Inc, AD9070/PCB Datasheet - Page 12

• Manufacturer Part Number: AD9070/PCB
• Description: BOARD EVAL FOR AD9070
• Manufacturer: Analog Devices Inc

Specifications of AD9070/PCB

• Rohs Status: RoHS non-compliant

AD9070
AD9070BR EVALUATION BOARD
The AD9070 evaluation board is a convenient and easy way to
evaluate the performance of the AD9070 in the SOIC package.
The board consists of an AD780 voltage reference (configured
for –2.5 V), two 10H176 (hex D flip flop) for capturing data
from the A/D converter and five 10H116 triple line receivers for
buffering the encode signal and driving the data via the edge
connector. Termination resistors (RP11, RP12, and RP14) are
provided for the data leaving the board via the connector; (they
can be removed if termination resistors are already provided by
the user).
Analog Input
The evaluation board requires a 1 V peak-to-peak signal centered
at ground (J1). This signal is ac-coupled and then dc shifted
–2.5 V before it is input to the A/D converter.
J4
J2
50
50
50
CLK
CLKB
AIN
1k
E8
E19
E9
1k
–5V
10H176
RECVR
ECL
E2
E3
BUFFERED
E1
LATCHED
ON-CARD
ENCODE
VREF OUT
VREF IN
AIN
COMP
BYPASS
AIN
ENC ENC
AND
AD9070
AD780 REFERENCE
E7
E4
E5
E6
HEX D FF
10H176
1 OF 2
PIN 2
CONNECTOR
PIN 21
10H116
1 OF 4
CARD
CONNECT
TO CARD
Encode
The AD9070 encode inputs can be driven single-ended (connect
E9 to E19 and drive J2 with an ECL signal) or differentially
(connect E8 to E19 and drive J2 and J4 with differential ECL
signals). The board is shipped in single ended configuration. The
differential encode signal leaving the board via the connector
can be inverted by interchanging E4, E5, E6, and E7 (connect
E4 to E7 and E5 to E6 or E4 to E6 and E7 to E5). This ensures
that the user will be able to capture the data coming from the
evaluation board.
Data Out
Data goes single-ended into the 10H116 flip flops but comes
out differentially. The data coming out of the AD9070 is in
two’s complement format, but is changed to straight binary by
inverting the MSB at the connector (on the schematic Bit 1 and
Bit 1B are swapped).
Voltage Reference
The AD9070 can be operated using its internal bandgap reference
(connect E2 to E3) or the on board AD780 external reference
(connect E1 to E3). The board is shipped utilizing the internal
voltage reference.
Layout
The AD9070 is not layout-sensitive if some important guidelines
are met. The evaluation board layout provides an example where
these guidelines have been followed to optimize performance.
•
•
•
The AD9070 evaluation board is provided as a design example
for customers of Analog Devices. ADI makes no warranties
express, statutory, or implied regarding merchantability or
fitness for a particular purpose.
Provide a good ground plane connecting the analog and
digital sections.
Excellent bypassing is essential. Chip caps with 0.1 µF values
and 0603 dimensions are placed flush against the pins. Placing
any of the caps on the bottom of the board can degrade
performance. These techniques reduce the amount of parasitic
inductance which can impact the bypassing ability of the caps.
Separate power planes and supplies for the analog and digital
sections are recommended.