AD9070

–12–

REV. B

AD9070BR EVALUATION BOARD

10H176

ECL

RECVR

E4

E6

PIN 2

E7

E5

PIN 21

BUFFERED

AND

LATCHED

ON-CARD

ENCODE

CARD

CONNECTOR

50

CLK

AIN

AIN

BYPASS

COMP

VREF IN

VREF OUT

ENC

ENC

1 OF 2

10H176

HEX D FF

TO CARD

CONNECT

1 OF 4

10H116

AD9070

1k

–5V

E19

E9

E8

CLKB

AIN

J2

J4

E1

E2

E3

AD780 REFERENCE

1k

50

50

Figure 23.

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.

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 twos

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 guide-

lines are met. The evaluation board layout provides an

example where these guidelines have been followed to

optimize performance.

• 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.

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.