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Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

AD8114/AD8115*

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 1998

Low Cost 225 MHz

16 Crosspoint Switches

FUNCTIONAL BLOCK DIAGRAM

AD8114/AD8115

OUTPUT
BUFFER

G = +1,

G = +2

256

80-BIT SHIFT REGISTER

WITH 5-BIT

PARALLEL LOADING

PARALLEL LATCH

DECODE

16 5:16 DECODERS

CLK

DATA IN

UPDATE

RESET

16 INPUTS

DATA
OUT

16
OUTPUTS

SET INDIVIDUAL OR

RESET ALL OUTPUTS

TO "OFF"

SER

/PAR

D0 D1 D2 D3 D4

ENABLE/DISABLE

SWITCH

MATRIX

FEATURES
16 16 High Speed Nonblocking Switch Arrays

AD8114; G = +1
AD8115; G = +2

Serial or Parallel Programming of Switch Array
Serial Data Out Allows "Daisy Chaining" of Multiple

16 16s to Create Larger Switch Arrays

High Impedance Output Disable Allows Connection of

Multiple Devices Without Loading the Output Bus

For Smaller Arrays See Our AD8108/AD8109 (8 8) or

AD8110/AD8111 (16 8) Switch Arrays

Complete Solution

Buffered Inputs
Programmable High Impedance Outputs
16 Output Amplifiers, AD8114 (G = +1), AD8115 (G = +2)
Drives 150 Loads

Excellent Video Performance

25 MHz, 0.1 dB Gain Flatness
0.05%/0.05 Differential Gain/Differential Phase Error

= 150 )

Excellent AC Performance

3 dB Bandwidth: 225 MHz
Slew Rate: 375 V/ s

Low Power of 700 mW (2.75 mW per Point)
Low All Hostile Crosstalk of 70 dB @ 5 MHz
Reset Pin Allows Disabling of All Outputs (Connected

Through a Capacitor to Ground Provides "Power-On"

Reset Capability)

100-Lead LQFP Package (14 mm 14 mm)

APPLICATIONS
Routing of High Speed Signals Including:

Video (NTSC, PAL, S, SECAM, YUV, RGB)
Compressed Video (MPEG, Wavelet)
3-Level Digital Video (HDB3)
Datacomms
Telecomms

PRODUCT DESCRIPTION

The AD8114/AD8115 are high speed 16

16 video crosspoint

switch matrices. They offer a 3 dB signal bandwidth greater
than 200 MHz and channel switch times of less than 50 ns with
1% settling. With 70 dB of crosstalk and 90 dB isolation (@
5 MHz), the AD8114/AD8115 are useful in many high speed
applications. The differential gain and differential phase of
better than 0.05% and 0.05

respectively, along with 0.1 dB

flatness out to 25 MHz while driving a 75

back-terminated

load, make the AD8114/AD8115 ideal for all types of signal
switching.

The AD8114 /AD8115 include 16 independent output buffers
that can be placed into a high impedance state for paralleling
crosspoint outputs so that off channels do not load the output
bus. The AD8114 has a gain of +1, while the AD8115 offers
a gain of +2. They operate on voltage supplies of

5 V while

consuming only 70 mA of idle current. The channel switching
is performed via a serial digital control (which can accommo-
date "daisy chaining" of several devices) or via a parallel control
allowing updating of an individual output without reprogram-
ming the entire array.

The AD8114/AD8115 is packaged in 100-lead LQFP package
and is available over the extended industrial temperature range
of 40

C to +85

*Patent Pending.

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AD8114/AD8115SPECIFICATIONS

AD8114 /AD8115

Parameter

Conditions

Min

Typ

Max

Units

DYNAMIC PERFORMANCE

3 dB Bandwidth

200 mV p-p, R

= 150

150/125

225/200

MHz

2 V p-p, R

= 150

100/125

MHz

Gain Flatness

0.1 dB, 200 mV p-p, R

= 150

25/40

MHz

0.1 dB, 2 V p-p, R

= 150

20/40

MHz

Propagation Delay

2 V p-p, R

= 150

Settling Time

0.1%, 2 V Step, R

= 150

Slew Rate

2 V Step, R

= 150

375/450

NOISE/DISTORTION PERFORMANCE

Differential Gain Error

NTSC or PAL, R

= 1 k

0.05

NTSC or PAL, R

= 150

0.05

Differential Phase Error

NTSC or PAL, R

= 1 k

0.05

Degrees

NTSC or PAL, R

= 150

0.05

Degrees

Crosstalk, All Hostile

f = 5 MHz

70/64

f = 10 MHz

60/52

Off Isolation, Input-Output

f = 10 MHz, R

= 150

, One Channel

Input Voltage Noise

0.01 MHz to 50 MHz

16/18

nV/

DC PERFORMANCE

Gain Error

No Load

0.05/0.2

0.08/0.6

= 1 k

0.05/0.2

= 150

0.2/0.35

Gain Matching

No Load, Channel-Channel

0.01/0.5

0.04/1

= 1 k

, Channel-Channel

0.01/0.5

Gain Temperature Coefficient

0.75/1.5

ppm/

OUTPUT CHARACTERISTICS

Output Impedance

DC, Enabled

0.2

Disabled

Output Disable Capacitance

Disabled

Output Leakage Current

Disabled

Output Voltage Range

No Load

3.0

3.3

Voltage Range

OUT

= 20 mA

2.5

Short Circuit Current

INPUT CHARACTERISTICS

Input Offset Voltage

Worst Case (All Configurations)

Temperature Coefficient

Input Voltage Range

No Load

1.5

3.5

Input Capacitance

Any Switch Configuration

Input Resistance

Input Bias Current

Per Output Selected

SWITCHING CHARACTERISTICS

Enable On Time

Switching Time, 2 V Step

50% UPDATE to 1% Settling

Switching Transient (Glitch)

20/30

mV p-p

POWER SUPPLIES

Supply Current

AVCC, Outputs Enabled, No Load

70/80

AVCC, Outputs Disabled

27/30

AVEE, Outputs Enabled, No Load

70/80

AVEE, Outputs Disabled

27/30

DVCC, Outputs Enabled, No Load

Supply Voltage Range

4.5 to

5.5

PSRR

f = 100 kHz

f = 1 MHz

OPERATING TEMPERATURE RANGE

Temperature Range

Operating (Still Air)

40 to +85

Operating (Still Air)

C/W

Specifications subject to change without notice.

= 5 V, T

= +25 C, R

= 1 k unless otherwise noted)

AD8114/AD8115

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CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD8114/AD8115 features proprietary ESD protection circuitry, permanent dam-
age may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.

WARNING!

ESD SENSITIVE DEVICE

MAXIMUM POWER DISSIPATION

The maximum power that can be safely dissipated by the
AD8114/AD8115 is limited by the associated rise in junction
temperature. The maximum safe junction temperature for plas-
tic encapsulated devices is determined by the glass transition
temperature of the plastic, approximately +150

C. Temporarily

exceeding this limit may cause a shift in parametric performance
due to a change in the stresses exerted on the die by the pack-
age. Exceeding a junction temperature of +175

C for an ex-

tended period can result in device failure.

While the AD8114/AD8115 is internally short circuit protected,
this may not be sufficient to guarantee that the maximum junc-
tion temperature (+150

C) is not exceeded under all conditions.

To ensure proper operation, it is necessary to observe the maxi-
mum power derating curves shown in Figure 3.

AMBIENT TEMPERATURE C

5.0

MAXIMUM POWER DISSIPATION Watts

4.0

50

40 30 20 10

30 40

60 70

3.0

2.0

1.0

= +150 C

Figure 3. Maximum Power Dissipation vs. Temperature

ABSOLUTE MAXIMUM RATINGS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.0 V
Internal Power Dissipation

AD8114/AD8115 100-Lead Plastic LQFP (ST) . . . . 2.6 W

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Output Short Circuit Duration

. . . . . . . . . . . . . . . . . . . . . . Observe Power Derating Curves

Storage Temperature Range . . . . . . . . . . . . 65

C to +125

Lead Temperature Range (Soldering 10 sec) . . . . . . . . +300

NOTES

Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.

Specification is for device in free air (T

= +25

C):

100-lead plastic LQFP (ST):

= 40

C/W.

ORDERING GUIDE

Temperature

Package

Model

Range

Description

Option

AD8114AST

C to +85

100-Lead Plastic LQFP (14 mm

14 mm)

ST-100

AD8115AST

C to +85

100-Lead Plastic LQFP (14 mm

14 mm)

ST-100

AD8114-EB

Evaluation Board

AD8115-EB

Evaluation Board

AD8114/AD8115

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Table III. Operation Truth Table

SER/

UPDATE

CLK

DATA IN

DATA OUT

RESET

PAR

Operation/Comment

No change in logic.

Data

i-80

The data on the serial DATA IN line is loaded
into serial register. The first bit clocked into
the serial register appears at DATA OUT 80
clocks later.

D0 . . . D4,

NA in Parallel

The data on the parallel data lines, D0D4, are

A0 . . . A3

Mode

loaded into the 80-bit serial shift register loca-
tion addressed by A0A3.

Data in the 80-bit shift register transfers into the
parallel latches that control the switch array.
Latches are transparent.

Asynchronous operation. All outputs are disabled.
Remainder of logic is unchanged.

CLK

4 TO 16 DECODER

CLK

UPDATE

256

DATA IN

(SERIAL)

(OUTPUT

ENABLE)

SER

/PAR

RESET

(OUTPUT ENABLE)

OUT0 EN

DATA
OUT

PARALLEL

DATA

D Q

CLK

D Q

CLK

D Q

CLK

D Q

CLK

D1
D2
D3

D Q

CLK

D Q

CLK

D Q

CLK

D Q

CLK

D Q

CLK

OUT1 EN

OUT2 EN

OUT3 EN

OUT4 EN

OUT5 EN

OUT6 EN

OUT7 EN

CLR

OUT15

OUTPUT ENABLE

SWITCH MATRIX

D Q

CLK

DECODE

CLR

OUT0

OUT1

CLR

OUT14

OUT15

D Q

CLK

OUT15

OUT8 EN

OUT9 EN

OUT10 EN

OUT11 EN

OUT12 EN

OUT13 EN

OUT14 EN

OUT15 EN

OUTPUT

ADDRESS

Figure 4. Logic Diagram

AD8114/AD8115

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PIN FUNCTION DESCRIPTIONS

Pin Name

Pin Numbers

Pin Description

INxx

58, 60, 62, 64, 66, 68, 70, 72,

Analog Inputs; xx = Channel Numbers 00 Through 15.

4, 6, 8, 10, 12, 14, 16, 18

DATA IN

Serial Data Input, TTL Compatible.

CLK

Clock, TTL Compatible. Falling Edge Triggered.

DATA OUT

Serial Data Out, TTL Compatible.

UPDATE

Enable (Transparent) "Low." Allows serial register to connect directly to switch matrix.
Data latched when "High."

RESET

100

Disable Outputs, Active "Low."

Chip Enable, Enable "Low." Must be "low" to clock in and latch data.

SER/PAR

Selects Serial Data Mode, "Low" or Parallel Data Mode, "High." Must be connected.

OUTyy

53, 51, 49, 47, 45, 43, 41, 39,

Analog Outputs yy = Channel Numbers 00 Through 15.

37, 35, 33, 31, 29, 27, 25, 23

AGND

3, 5, 7, 9, 11, 13, 15, 17, 19, 57,

Analog Ground for Inputs and Switch Matrix. Must be connected.

59, 61, 63, 65, 67, 69, 71, 73

DVCC

1, 75

+5 V for Digital Circuitry.

DGND

2, 74

Ground for Digital Circuitry.

AVEE

20, 56

5 V for Inputs and Switch Matrix.

AVCC

21, 55

+5 V for Inputs and Switch Matrix.

AVCCxx/yy

54, 50, 46, 42, 38, 34, 30, 26, 22

+5 V for Output Amplifier that is shared by Channel Numbers xx and yy. Must be connected.

AVEExx/yy

52, 48, 44, 40, 36, 32, 28, 24

5 V for Output Amplifier that is shared by Channel Numbers xx and yy. Must be connected.

Parallel Data Input, TTL Compatible (Output Select LSB).

Parallel Data Input, TTL Compatible (Output Select).

Parallel Data Input, TTL Compatible (Output Select MSB).

Parallel Data Input, TTL Compatible (Input Select LSB).

Parallel Data Input, TTL Compatible (Input Select).

Parallel Data Input, TTL Compatible (Input Select MSB).

Parallel Data Input, TTL Compatible (Output Enable).

8593

No Connect.

Figure 5. I/O Schematics

ESD

INPUT

ESD

OUTPUT

ESD

RESET

20k

DGND

ESD

INPUT

DGND

ESD

OUTPUT

DGND

a. Analog Input

c. Reset Input

b. Analog Output

d. Logic Input

e. Logic Output

AD8114/AD8115

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PIN CONFIGURATION

RESET

DATA OUT

CLK

DATA IN

UPDATE

SER

/PAR

AVCC13/14

OUT13

AVEE12/13

OUT12

AVCC11/12

OUT11

AVEE10/11

OUT10

AVCC09/10

OUT09

AVEE08/09

OUT08

AVCC07/08

OUT07

AVEE06/07

OUT06

AVCC05/06

OUT05

AVEE04/05

DVCC

DGND

AGND

IN07

AGND

IN06

AGND

IN05

AGND

IN04

AGND

IN03

AGND

IN02

AGND

IN01

AGND

IN00

AGND

AVEE

AVCC

AVCC00

OUT00

AVEE00/01

OUT01

DVCC

DGND

AGND

IN08

AGND

IN09

AGND

IN10

AGND

IN11

AGND

IN12

AGND

IN13

AGND

IN14

AGND

IN15

AGND

AVEE

AVCC

AVCC15

OUT15

AVEE14/15

OUT14

OUT04

AVCC03/04

OUT03

AVEE02/03

OUT02

AVCC01/02

PIN 1
IDENTIFIER

TOP VIEW

(Not to Scale)

AD8114/AD8115

NC = NO CONNECT

AD8114/AD8115

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Typical Performance Characteristics

FREQUENCY MHz

0.1

GAIN dB

100

1000

AS SHOWN

= 150

GAIN

FLATNESS

2V p-p

200mV p-p

0.2

0.1

0.3

0.4

0.5

FLATNESS dB

0.6

Figure 6. AD8114 Frequency Response; R

= 150

FREQUENCY MHz

GAIN dB

0.6

0.2

0.1

0.3

0.4

0.5

FLATNESS dB

0.1

100

1000

0.3

0.4

GAIN

FLATNESS

AS SHOWN

= 1k

2V p-p

200mV p-p

Figure 7. AD8114 Frequency Response; R

= 1 k

FREQUENCY MHz

GAIN dB

0.1

100

1000

= 200mV p-p

AS SHOWN

= 18pF

= 1k

= 150

Figure 8. AD8114 Frequency Response vs. Load Impedance

FREQUENCY MHz

GAIN dB

0.2

0.1

0.3

0.4

0.5

FLATNESS dB

0.1

100

1000

0.3

0.4

GAIN

FLATNESS

AS SHOWN

= 150

2V p-p

200mV p-p

0.5

200mV p-p
2V p-p

Figure 9. AD8115 Frequency Response; R

= 150

FREQUENCY MHz

GAIN dB

0.2

0.1

0.3

0.4

0.5

FLATNESS dB

0.1

100

1000

0.3

0.4

GAIN

FLATNESS

2V p-p

200mV p-p

0.5

AS SHOWN

= 1k

200mV p-p
2V p-p

Figure 10. AD8115 Frequency Response; R

= 1 k

FREQUENCY MHz

GAIN dB

10

0.1

100

1000

= 200mV p-p

AS SHOWN

= 18pF

= 1k

= 150

Figure 11. AD8115 Frequency Response vs. Load Impedance

AD8114/AD8115

REV. 0

THEORY OF OPERATION

The AD8114 (G = +1) and AD8115 (G = +2) are crosspoint
arrays with 16 outputs, each of which can be connected to any
one of 16 inputs. Organized by output row, 16 switchable trans-
conductance stages are connected to each output buffer, in the
form of a 16-to-1 multiplexer. Each of the 16 rows of transconduc-
tance stages are wired in parallel to the 16 input pins, for a total
array of 256 transconductance stages. Decoding logic for each
output selects one (or none) of the transconductance stages to
drive the output stage. The transconductance stages are NPN-
input differential pairs, sourcing current into the folded cascode
output stage. The compensation network and emitter follower
output buffer are in the output stage. Voltage feedback sets the
gain, with the AD8114 being configured as a unity gain follower,
and the AD8115 as a gain-of-two amplifier with a feedback
network.

This architecture provides drive for a reverse-terminated video
load (150

), with low differential gain and phase error for

relatively low power consumption. Power consumption is fur-
ther reduced by disabling outputs and transconductance stages
that are not in use. The user will notice a small increase in input
bias current as each transconductance stage is enabled.

Features of the AD8114 and AD8115 simplify the construction
of larger switch matrices. The unused outputs of both devices
can be disabled to a high impedance state, allowing the outputs
of multiple ICs to be bused together. In the case of the AD8115, a
feedback isolation scheme is used so that the impedance of the
gain-of-two feedback network does not load the output. Because
no additional input buffering is necessary, high input resistance
and low input capacitance are easily achieved without additional
signal degradation. To control enable glitches, it is recommended
that the disabled output voltage be maintained within its normal
enabled voltage range (

3.3 V). If necessary, the disabled out-

put can be kept from drifting out of range by applying an output
load resistor to ground.

A flexible TTL-compatible logic interface simplifies the pro-
gramming of the matrix. Both parallel and serial loading into a
first rank of latches programs each output. A global latch simul-
taneously updates all outputs. A power-on reset pin is available
to avoid bus conflicts by disabling all outputs.

APPLICATIONS

The AD8114/AD8115 have two options for changing the pro-
gramming of the crosspoint matrix. In the first option a serial
word of 80 bits can be provided that will update the entire ma-
trix each time. The second option allows for changing a single
output's programming via a parallel interface. The serial option
requires fewer signals, but more time (clock cycles) for changing
the programming, while the parallel programming technique re-
quires more signals, but can change a single output at a time
and requires fewer clock cycles to complete programming.

Serial Programming

The serial programming mode uses the device pins CE, CLK,
DATA IN, UPDATE and SER/PAR. The first step is to assert a
LOW on SER/PAR in order to enable the serial programming
mode. CE for the chip must be LOW to allow data to be clocked
into the device. The CE signal can be used to address an indi-
vidual device when devices are connected in parallel.

The UPDATE signal should be HIGH during the time that data
is shifted into the device's serial port. Although the data will still

shift in when UPDATE is LOW, the transparent, asynchronous
latches will allow the shifting data to reach the matrix. This will
cause the matrix to try to update to every intermediate state as
defined by the shifting data.

The data at DATA IN is clocked in at every down edge of CLK.
A total of 80 bits must be shifted in to complete the program-
ming. For each of the 16 outputs, there are four bits (D0D3)
that determine the source of its input followed by one bit (D4)
that determines the enabled state of the output. If D4 is LOW
(output disabled), the four associated bits (D0D3) do not
matter, because no input will be switched to that output.

The most-significant-output-address data is shifted in first, then
following in sequence until the least-significant-output-address
data is shifted in. At this point UPDATE can be taken LOW,
which will cause the programming of the device according to the
data that was just shifted in. The UPDATE registers are asyn-
chronous and when UPDATE is LOW (and CE is LOW), they
are transparent.

If more than one AD8114/AD8115 device is to be serially pro-
grammed in a system, the DATA OUT signal from one device
can be connected to the DATA IN of the next device to form a
serial chain. All of the CLK, CE, UPDATE and SER/PAR pins
should be connected in parallel and operated as described above.
The serial data is input to the DATA IN pin of the first device
of the chain, and it will ripple on through to the last. Therefore,
the data for the last device in the chain should come at the be-
ginning of the programming sequence. The length of the pro-
gramming sequence will be 80 bits times the number of devices
in the chain.

Parallel Programming

When using the parallel programming mode, it is not necessary
to reprogram the entire device when making changes to the
matrix. In fact, parallel programming allows the modification
of a single output at a time. Since this takes only one CLK/
UPDATE cycle, significant time savings can be realized by
using parallel programming.

One important consideration in using parallel programming is
that the RESET signal DOES NOT RESET ALL REGISTERS
in the AD8114/AD8115. When taken low, the RESET signal
will only set each output to the disabled state. This is helpful
during power-up to ensure that two parallel outputs will not be
active at the same time.

After initial power-up, the internal registers in the device will
generally have random data, even though the RESET signal has
been asserted. If parallel programming is used to program one
output, then that output will be properly programmed, but the
rest of the device will have a random program state depending
on the internal register content at power-up. Therefore, when
using parallel programming, it is essential that ALL OUTPUTS
BE PROGRAMMED TO A DESIRED STATE AFTER
POWER-UP. This will ensure that the programming matrix is
always in a known state. From then on, parallel programming
can be used to modify a single output or more at a time.

In similar fashion, if both CE and UPDATE are taken LOW
after initial power-up, the random power-up data in the shift
register will be programmed into the matrix. Therefore, in order
to prevent the crosspoint from being programmed into an un-
known state DO NOT APPLY LOW LOGIC LEVELS TO
BOTH CE AND UPDATE AFTER POWER IS INITIALLY

AD8114/AD8115

REV. 0

APPLIED. Programming the full shift register one time to a
desired state, either by serial or parallel programming after
initial power-up, will eliminate the possibility of programming
the matrix to an unknown state.

To change an output's programming via parallel programming,
SER/PAR and UPDATE should be taken HIGH and CE should
be taken LOW. The CLK signal should be in the HIGH state.
The 4-bit address of the output to be programmed should be put
on A0A3. The first four data bits (D0D3) should contain the
information that identifies the input that gets programmed to the
output that is addressed. The fourth data bit (D4) will deter-
mine the enabled state of the output. If D4 is LOW (output
disabled) then the data on D0D3 does not matter.

After the desired address and data signals have been established,
they can be latched into the shift register by a HIGH to LOW
transition of the CLK signal. The matrix will not be programmed,
however, until the UPDATE signal is taken low. It is thus pos-
sible to latch in new data for several or all of the outputs first via
successive negative transitions of CLK while UPDATE is held
high, and then have all the new data take effect when UPDATE
goes LOW. This is the technique that should be used when
programming the device for the first time after power-up when
using parallel programming.

POWER-ON RESET

When powering up the AD8114/AD8115 it is usually desirable
to have the outputs come up in the disabled state. The RESET
pin, when taken LOW will cause all outputs to be in the dis-
abled state. However, the RESET signal DOES NOT RESET
ALL REGISTERS in the AD8114/AD8115 This is important
when operating in the parallel programming mode. Please refer
to that section for information about programming internal
registers after power-up. Serial programming will program the
entire matrix each time, so no special considerations apply.

Since the data in the shift register is random after power-up,
they should not be used to program the matrix or else the matrix
can enter unknown states. To prevent this, DO NOT APPLY
LOGIC LOW SIGNALS TO BOTH CE AND UPDATE
INITIALLY AFTER POWER-UP. The shift register should
first be loaded with the desired data, and then UPDATE can be
taken LOW to program the device.

The RESET pin has a 20 k

pull-up resistor to DVDD that can

be used to create a simple power-up reset circuit. A capacitor
from RESET to ground will hold RESET LOW for some time
while the rest of the device stabilizes. The LOW condition will
cause all the outputs to be disabled. The capacitor will then
charge through the pull-up resistor to the HIGH state, thus
allowing full programming capability of the device.

GAIN SELECTION

The 16

16 crosspoints come in two versions, depending on the

gain of the analog circuit paths that is desired. The AD8114
device is unity gain and can be used for analog logic switching
and other applications where unity gain is desired. The AD8114
can also be used for the input and interior sections of larger
crosspoint arrays where termination of output signals is not
usually used. The AD8114 outputs have a very high impedance
when their outputs are disabled.

The AD8115 can be used for devices that will be used to drive
a terminated cable with its outputs. This device has a built-in
gain-of-two that eliminates the need for a gain-of-two buffer to

drive a video line. Its high output disabled impedance minimizes
signal degradation when paralleling additional outputs.

CREATING LARGER CROSSPOINT ARRAYS

The AD8114/AD8115 are high density building blocks for cre-
ating crosspoint arrays of dimensions larger than 16

16. Vari-

ous features, such as output disable, chip enable, and gain-
of-one and gain-of-two options, are useful for creating larger
arrays. When required for customizing a crosspoint array size,
they can be used with the AD8108 and AD8109, a pair (unity
gain and gain-of-two) of 8

8 video crosspoint switches, or the

AD8110 and AD8111, a pair (unity gain and gain-of-two)
16

8 video crosspoint switches.

The first consideration in constructing a larger crosspoint is to
determine the minimum number of devices are required. The
16

16 architecture of the AD8114/AD8115 contains 256

"points," which is a factor of 64 greater than a 4

1 crosspoint

(or multiplexer). The PC board area, power consumption and
design effort savings are readily apparent when compared to
using these smaller devices.

For a nonblocking crosspoint, the number of points required is
the product of the number of inputs multiplied by the number
of outputs. Nonblocking requires that the programming of a
given input to one or more outputs does not restrict the avail-
ability of that input to be a source for any other outputs.

Some nonblocking crosspoint architectures will require more
than this minimum as calculated above. Also, there are blocking
architectures that can be constructed with fewer devices than
this minimum. These systems have connectivity available on a
statistical basis that is determined when designing the overall
system.

The basic concept in constructing larger crosspoint arrays is
to connect inputs in parallel in a horizontal direction and to
"wire-OR" the outputs together in the vertical direction. The
meaning of horizontal and vertical can best be understood by
looking at a diagram. Figure 42 illustrates this concept for a
32

32 crosspoint array that uses four AD8114s or AD8115s.

AD8114

AD8115

AD8114

AD8115

TERM

IN 0015

TERM

IN 1631

AD8114

AD8115

AD8114

AD8115

Figure 42. 32

32 Crosspoint Array Using Four AD8114s

or Four AD8115s

The inputs are each uniquely assigned to each of the 32 inputs
of the two devices and terminated appropriately. The outputs
are wired-ORed together in pairs. The output from only one of
a wire-ORed pair should be enabled at any given time. The
device programming software must be properly written to cause
this to happen.

Using additional crosspoint devices in the design can lower the
number of outputs that have to be wire-ORed together. Figure
43 shows a block diagram of a system using eight AD8114s and

AD8114/AD8115

REV. 0

two AD8115s to create a nonblocking, gain-of-two, 128

crosspoint that restricts the wire-ORing at the output to only
four outputs.

Additionally, by using the lower eight outputs from each of the
two Rank 2 AD8115s, a blocking 128

32 crosspoint array can

be realized. There are, however, some drawbacks to this tech-
nique. The offset voltages of the various cascaded devices will
accumulate and the bandwidth limitations of the devices will
compound. In addition, the extra devices will consume more
current and take up more board space. Once again, the overall
system design specifications will determine how to make the
various tradeoffs.

Multichannel Video

The excellent video specifications of the AD8114/AD8115 make
them ideal candidates for creating composite video crosspoint
switches. These can be made quite dense by taking advantage of
the AD8114/AD8115's high level of integration and the fact that
composite video requires only one crosspoint channel per sys-
tem video channel. There are, however, other video formats that
can be routed with the AD8114/AD8115 requiring more than
one crosspoint channel per video channel.

Some systems use twisted-pair wiring to carry video signals.
These systems utilize differential signals and can lower costs
because they use lower cost cables, connectors and termination
methods. They also have the ability to lower crosstalk and reject
common-mode signals, which can be important for equipment

that operates in noisy environments or where common-mode
voltages are present between transmitting and receiving equipment.

In such systems, the video signals are differential; there is a
positive and negative (or inverted) version of the signals. These
complementary signals are transmitted onto each of the two
wires of the twisted pair, yielding a first order zero common-
mode voltage. At the receive end, the signals are differentially
received and converted back into a single-ended signal.

When switching these differential signals, two channels are
required in the switching element to handle the two differential
signals that make up the video channel. Thus, one differential
video channel is assigned to a pair of crosspoint channels, both
input and output. For a single AD8114/AD8115, eight differential
video channels can be assigned to the 16 inputs and 16 outputs.
This will effectively form an 8

8 differential crosspoint switch.

Programming such a device will require that inputs and outputs
be programmed in pairs. This information can be deduced by
inspection of the programming format of the AD8114/AD8115
and the requirements of the system.

There are other analog video formats requiring more than one
analog circuit per video channel. One two-circuit format that is
commonly being used in systems such as satellite TV, digital
cable boxes and higher quality VCRs, is called S-video or Y/C
video. This format carries the brightness (luminance or Y)
portion of the video signal on one channel and the color (chromi-
nance, chroma or C) on a second channel.

TERM

IN 0015

IN 1631

IN 3247

IN 4863

IN 6479

IN 8095

IN 96111

IN 112127

RANK 2

32:16 NONBLOCKING

(32:32 BLOCKING)

RANK 1

(8 AD8114)

128:32

TERM

AD8115

8
1k

AD8115

OUT 0015
NONBLOCKING

ADDITIONAL
16 OUTPUTS
(SUBJECT
TO BLOCKING)

AD8114

Figure 43. Nonblocking 128

16 Array (128

32 Blocking)

AD8114/AD8115

REV. 0

Since S-video also uses two separate circuits for one video chan-
nel, creating a crosspoint system requires assigning one video
channel to two crosspoint channels as in the case of a differen-
tial video system. Aside from the nature of the video format,
other aspects of these two systems will be the same.

There are yet other video formats using three channels to carry
the video information. Video cameras produce RGB (red, green,
blue) directly from the image sensors. RGB is also the usual
format used by computers internally for graphics. RGB can also
be converted to Y, R-Y, B-Y format, sometimes called YUV
format. These three-circuit, video standards are referred to as
component analog video.

The component video standards require three crosspoint chan-
nels per video channel to handle the switching function. In a
fashion similar to the two-circuit video formats, the inputs and
outputs are assigned in groups of three and the appropriate logic
programming is performed to route the video signals.

CROSSTALK

Many systems, such as broadcast video, that handle numerous
analog signal channels have strict requirements for keeping the
various signals from influencing any of the others in the system.
Crosstalk is the term used to describe the coupling of the signals
of other nearby channels to a given channel.

When there are many signals in close proximity in a system, as
will undoubtedly be the case in a system that uses the AD8114/
AD8115, the crosstalk issues can be quite complex. A good
understanding of the nature of crosstalk and some definition of
terms is required in order to specify a system that uses one or
more AD8114/AD8115s.

Types of Crosstalk

Crosstalk can be propagated by means of any of three methods.
These fall into the categories of electric field, magnetic field and
sharing of common impedances. This section will explain these
effects.

Every conductor can be both a radiator of electric fields and a
receiver of electric fields. The electric field crosstalk mechanism
occurs when the electric field created by the transmitter propa-
gates across a stray capacitance (e.g., free space) and couples
with the receiver and induces a voltage. This voltage is an un-
wanted crosstalk signal in any channel that receives it.

Currents flowing in conductors create magnetic fields that circu-
late around the currents. These magnetic fields will then gener-
ate voltages in any other conductors whose paths they link. The
undesired induced voltages in these other channels are crosstalk
signals. The channels that crosstalk can be said to have a mutual
inductance that couples signals from one channel to another.

The power supplies, grounds and other signal return paths of a
multichannel system are generally shared by the various chan-
nels. When a current from one channel flows in one of these
paths, a voltage that is developed across the impedance becomes
an input crosstalk signal for other channels that share the com-
mon impedance.

All these sources of crosstalk are vector quantities, so the
magnitudes cannot simply be added together to obtain the total
crosstalk. In fact, there are conditions where driving additional
circuits in parallel in a given configuration can actually reduce
the crosstalk.

Areas of Crosstalk

For a practical AD8114/AD8115 circuit, it is required that it be
mounted to some sort of circuit board in order to connect it to
power supplies and measurement equipment. Great care has
been taken to create a characterization board (also available as
an evaluation board) that adds minimum crosstalk to the intrin-
sic device. This, however, raises the issue that a system's crosstalk
is a combination of the intrinsic crosstalk of the devices in addi-
tion to the circuit board to which they are mounted. It is impor-
tant to try to separate these two areas of crosstalk when attempting
to minimize its effect.

In addition, crosstalk can occur among the inputs to a cross-
point and among the output. It can also occur from input to
output. Techniques will be discussed for diagnosing which part
of a system is contributing to crosstalk.

Measuring Crosstalk

Crosstalk is measured by applying a signal to one or more chan-
nels and measuring the relative strength of that signal on a de-
sired selected channel. The measurement is usually expressed as
dB down from the magnitude of the test signal. The crosstalk is
expressed by:

|XT| = 20 log

(Asel(s)/Atest(s))

where s = jw is the Laplace transform variable, Asel(s) is the
amplitude of the crosstalk-induced signal in the selected channel
and Atest(s) is the amplitude of the test signal. It can be seen
that crosstalk is a function of frequency, but not a function of
the magnitude of the test signal (to first order). In addition, the
crosstalk signal will have a phase relative to the test signal asso-
ciated with it.

A network analyzer is most commonly used to measure crosstalk
over a frequency range of interest. It can provide both magni-
tude and phase information about the crosstalk signal.

As a crosspoint system or device grows larger, the number of
theoretical crosstalk combinations and permutations can be-
come extremely large. For example, in the case of the 16

matrix of the AD8114/AD8115, we can examine the number of
crosstalk terms that can be considered for a single channel, say
IN00 input. IN00 is programmed to connect to one of the
AD8114/AD8115 outputs where the measurement can be made.

First, we can measure the crosstalk terms associated with driv-
ing a test signal into each of the other 15 inputs one at a time,
while applying no signal to IN00. We can then measure the
crosstalk terms associated with driving a parallel test signal into
all 15 other inputs taken two at a time in all possible combina-
tions; and then three at a time, etc., until, finally, there is only
one way to drive a test signal into all 15 other inputs in parallel.

Each of these cases is legitimately different from the others and
might yield a unique value depending on the resolution of the
measurement system, but it is hardly practical to measure all
these terms and then to specify them. In addition, this describes
the crosstalk matrix for just one input channel. A similar cross-
talk matrix can be proposed for every other input. In addition, if
the possible combinations and permutations for connecting
inputs to the other (not used for measurement) outputs are
taken into consideration, the numbers rather quickly grow to
astronomical proportions. If a larger crosspoint array of multiple
AD8114/AD8115s is constructed, the numbers grow larger still.

Obviously, some subset of all these cases must be selected to
be used as a guide for a practical measure of crosstalk. One

AD8114/AD8115

REV. 0

common method is to measure "all hostile" crosstalk. This term
means that the crosstalk to the selected channel is measured
while all other system channels are driven in parallel. In general,
this will yield the worst crosstalk number, but this is not always
the case due to the vector nature of the crosstalk signal.

Other useful crosstalk measurements are those created by one
nearest neighbor or by the two nearest neighbors on either side.
These crosstalk measurements will generally be higher than
those of more distant channels, so they can serve as a worst case
measure for any other one-channel or two-channel crosstalk
measurements.

Input and Output Crosstalk

The flexible programming capability of the AD8114/AD8115
can be used to diagnose whether crosstalk is occurring more on
the input side or the output side. Some examples are illustrative.
A given input channel (IN07 in the middle for this example) can
be programmed to drive OUT07 (also in the middle). The input
to IN07 is just terminated to ground (via 50

or 75

) and no

signal is applied.

All the other inputs are driven in parallel with the same test
signal (practically provided by a distribution amplifier), with all
other outputs except OUT07 disabled. Since grounded IN07 is
programmed to drive OUT07, no signal should be present. Any
signal that is present can be attributed to the other 15 hostile
input signals, because no other outputs are driven (they are all
disabled). Thus, this method measures the all-hostile input
contribution to crosstalk into IN07. Of course, the method can
be used for other input channels and combinations of hostile
inputs.

For output crosstalk measurement, a single input channel is
driven (IN00 for example) and all outputs other than a given
output (IN07 in the middle) are programmed to connect to
IN00. OUT07 is programmed to connect to IN15 (far away
from IN00), which is terminated to ground. Thus OUT07
should not have a signal present since it is listening to a quiet
input. Any signal measured at the OUT07 can be attributed to
the output crosstalk of the other 16 hostile outputs. Again, this
method can be modified to measure other channels and other
crosspoint matrix combinations.

Effect of Impedances on Crosstalk

The input side crosstalk can be influenced by the output imped-
ance of the sources that drive the inputs. The lower the imped-
ance of the drive source, the lower the magnitude of the crosstalk.
The dominant crosstalk mechanism on the input side is capaci-
tive coupling. The high impedance inputs do not have signifi-
cant current flow to create magnetically induced crosstalk.
However, significant current can flow through the input termi-
nation resistors and the loops that drive them. Thus, the PC
board on the input side can contribute to magnetically coupled
crosstalk.

From a circuit standpoint, the input crosstalk mechanism looks
like a capacitor coupling to a resistive load. For low frequencies
the magnitude of the crosstalk will be given by:

|XT| = 20 log

[(R

)

where R

is the source resistance, C

is the mutual capacitance

between the test signal circuit and the selected circuit, and s is
the Laplace transform variable.

From the equation it can be observed that this crosstalk mecha-
nism has a high-pass nature; it can be also minimized by

reducing the coupling capacitance of the input circuits and
lowering the output impedance of the drivers. If the input is
driven from a 75

terminated cable, the input crosstalk can be

reduced by buffering this signal with a low output impedance
buffer.

On the output side, the crosstalk can be reduced by driving a
lighter load. Although the AD8114/AD8115 is specified with
excellent differential gain and phase when driving a standard
150

video load, the crosstalk will be higher than the minimum

obtainable due to the high output currents. These currents will
induce crosstalk via the mutual inductance of the output pins
and bond wires of the AD8114/AD8115.

From a circuit standpoint, this output crosstalk mechanism
looks like a transformer with a mutual inductance between the
windings that drives a load resistor. For low frequencies, the
magnitude of the crosstalk is given by:

|XT| = 20 log

(Mxy

s/R

)

where Mxy is the mutual inductance of output X to output Y
and R

is the load resistance on the measured output. This

crosstalk mechanism can be minimized by keeping the mutual
inductance low and increasing R

. The mutual inductance can

be kept low by increasing the spacing of the conductors and
minimizing their parallel length.

PCB Layout

Extreme care must be exercised to minimize additional crosstalk
generated by the system circuit board(s). The areas that must be
carefully detailed are grounding, shielding, signal routing and
supply bypassing.

The packaging of the AD8114/AD8115 is designed to help keep
the crosstalk to a minimum. Each input is separated from each
other input by an analog ground pin. All of these AGNDs should
be directly connected to the ground plane of the circuit board.
These ground pins provide shielding, low impedance return
paths and physical separation for the inputs. All of these help to
reduce crosstalk.

Each output is separated from its two neighboring outputs by an
analog supply pin of one polarity or the other. Each of these
analog supply pins provides power to the output stages of only
the two nearest outputs. These supply pins provide shielding,
physical separation and a low impedance supply for the outputs.
Individual bypassing of each of these supply pins with a 0.01

chip capacitor directly to the ground plane minimizes high fre-
quency output crosstalk via the mechanism of sharing common
impedances.

Each output also has an on-chip compensation capacitor that
is individually tied to the nearby analog ground pins AGND00
through AGND07. This technique reduces crosstalk by prevent-
ing the currents that flow in these paths from sharing a common
impedance on the IC and in the package pins. These AGNDxx
signals should all be connected directly to the ground plane.

The input and output signals will have minimum crosstalk if
they are located between ground planes on layers above and
below, and separated by ground in between. Vias should be
located as close to the IC as possible to carry the inputs and
outputs to the inner layer. The only place the input and output
signals surface is at the input termination resistors and the out-
put series back-termination resistors. To the extent possible,
these signals should also be separated as soon as they emerge
from the IC package.

AD8114/AD8115

REV. 0

57,59

INPUT 00

AGND

0.01 F

INPUT 01

AGND

INPUT 02

AGND

INPUT 03

AGND

INPUT 04

AGND

INPUT 05

AGND

INPUT 06

AGND

INPUT 07

INPUT 08

AGND

INPUT 09

AGND

INPUT 10

AGND

INPUT 11

AGND

INPUT 12

AGND

INPUT 13

AGND

INPUT 14

AGND

INPUT 15

AGND

DATA OUT

DATA IN

P2-5

P2-4

P2-2

P2-3

P2-1

P2-6

RESET

DGND

CLK

UPDATE

SER

/PAR

P3-1

P3-2

P3-3

P3-4

P3-5

P3-6

P3-7

P3-8

P3-9

P3-10

P3-11

P3-12

P3-13

P3-14

2,74 100

95 84

82 81 80 79 78 77 76

SERIAL MODE
JUMP

R33

20k

DVCC

OUTPUT 00

0.01 F

20, 56

AVEE

0.01 F

21, 55

AVCC

0.01 F

1, 75

DVCC

AD8114/
AD8115

DVCC DGND

AVEE AGND AVCC

P1-1

P1-2

P1-3

P1-4

P1-5

P1-6

P1-7

0.1 F 10 F

JUMPER

3,73

AGND

NOTE
R = OPTIONAL 50 TERMINATOR RESISTORS
C = OPTIONAL SMOOTHING CAPACITOR

NO CONNECT:

85-93

AVCC

OUTPUT 00

0.01 F

OUTPUT 01

AVEE

OUTPUT 01

0.01 F

OUTPUT 02

AVCC

OUTPUT 02

0.01 F

OUTPUT 03

AVEE

OUTPUT 03

0.01 F

OUTPUT 04

AVCC

OUTPUT 04

0.01 F

OUTPUT 05

AVEE

OUTPUT 05

0.01 F

OUTPUT 06

AVCC

OUTPUT 06

0.01 F

OUTPUT 07

AVEE

OUTPUT 07

0.01 F

OUTPUT 08

AVCC

OUTPUT 08

0.01 F

OUTPUT 09

AVEE

OUTPUT 09

0.01 F

OUTPUT 10

AVCC

OUTPUT 10

0.01 F

OUTPUT 11

AVEE

OUTPUT 11

0.01 F

OUTPUT 12

AVCC

OUTPUT 12

0.01 F

OUTPUT 13

AVEE

OUTPUT 13

0.01 F

OUTPUT 14

AVCC

OUTPUT 14

0.01 F

OUTPUT 15

AVEE

OUTPUT 15

AVCC

DVCC

Figure 44. Evaluation Board Schematic

AD8114/AD8115

REV. 0

RESET

CLK

DATA IN

DGND

UPDATE

MOLEX 0.100" CENTER

CRIMP TERMINAL HOUSING

D-SUB 25 PIN (MALE)

EVALUATION BOARD

2
3
4
5
6
25

3
1
4
5
2
6

SIGNAL

CE
RESET
UPDATE

DATA IN
CLK
DGND

MOLEX

TERMINAL HOUSING

D-SUB-25

Figure 52. Evaluation Board-PC Connection Cable

Optimized for video applications, all signal inputs and outputs
are terminated with 75

resistors. Stripline techniques are used

to achieve a characteristic impedance on the signal input and
output lines, also of 75

. Figure 51 shows a cross-section of one

of the input or output tracks along with the arrangement of the
PCB layers. It should be noted that unused regions of the four
layers are filled up with ground planes. As a result, the input and
output traces, in addition to having controlled impedances, are
well shielded.

w = 0.008"

(0.2mm)

a = 0.008"

(0.2mm)

b = 0.0514"

(1.3mm)

h = 0.025"

(0.63mm)

t = 0.00135" (0.0343mm)

TOP LAYER

SIGNAL LAYER

POWER LAYER

BOTTOM LAYER

Figure 51. Cross Section of Input and Output Traces

The board has 32 BNC type connectors: 16 inputs and 16
outputs. The connectors are arranged in a crescent around the
device. As can be seen from Figure 47, this results in all 16
input signal traces and all 16 signal output traces having the
same length. This is useful in tests such as All-Hostile
Crosstalk where the phase relationship and delay between
signals needs to be maintained from input to output.

The three power supply pins AVCC, DVCC and AVEE should
be connected to good quality, low noise,

5 V supplies. Where

the same

5 V power supplies are used for analog and digital,

separate cables should be run for the power supply to the
evaluation board's analog and digital power supply pins.

As a general rule, each power supply pin (or group of adjacent
power supply pins) should be locally decoupled with a 0.01

capacitor. If there is a space constraint, it is more important to
decouple analog power supply pins before digital power supply
pins. A 0.1

F capacitor, located reasonably close to the pins,

can be used to decouple a number of power supply pins. Fi-
nally a 10

F capacitor should be used to decouple power sup-

plies as they come onto the board.

AD8114/AD8115

REV. 0

Controlling the Evaluation Board from a PC

The evaluation board includes Windows

-based control soft-

ware and a custom cable that connects the board's digital inter-
face to the printer port of the PC. The wiring of this cable is
shown in Figure 52. The software requires Windows 3.1 or later
to operate. To install the software, insert the disk labeled "Disk
#1 of 2" in the PC and run the file called SETUP.EXE. Addi-
tional installation instructions will be given on-screen. Before
beginning installation, it is important to terminate any other
Windows applications that are running.

When you launch the crosspoint control software, you will be
asked to select the printer port you are using. Most modern PCs
have only one printer port, usually called LPT1. However some
laptop computers use the PRN port.

Figure 53 shows the main screen of the control software in its
initial reset state (all outputs off). Using the mouse, any input
can be connected with one or more outputs by simply clicking
on the appropriate radio buttons in the 16

16 on-screen array.

Each time a button is clicked on, the software automatically
sends and latches the required 80-bit data stream to the evalua-
tion board. An output can be turned off by clicking the appro-
priate button in the Off column. To turn off all outputs, click on
RESET.

While the computer software only supports serial programming
via a PC's parallel port and the provided cable, the evaluation
board has a connector that can be used for parallel program-
ming. The SER/PAR signal should be at a logic high to use
parallel programming. There is no cable nor software provided
with the evaluation board for parallel programming. These are
left to the user to provide.

The software offers volatile and nonvolatile storage of configura-
tions. For volatile storage, up to two configurations can be stored
and recalled using the Memory 1 and Memory 2 Buffers. These
function in a fashion identical to the memory on a pocket calcu-
lator. For nonvolatile storage of a configuration, the Save Setup
and Load Setup functions can be used. This stores the configu-
ration as a data file on disk.

Overshoot on PC Printer Ports' Data Lines

The data lines on some printer ports have excessive overshoot.
Overshoot on the pin that is used as the serial clock (Pin 6 on
the D-Sub-25 connector) can cause communication problems.
This overshoot can be eliminated by connecting a capacitor
from the CLK line on the evaluation board to ground. A pad
has been provided on the circuit-side (C33) of the evaluation
board to allow this capacitor to be soldered into place. Depend-
ing upon the overshoot from the printer port, this capacitor may
need to be as large as 0.01

Windows is a registered trademark of Microsoft Corporation.

AD8114/AD8115

Parallel Port Selection

Figure 53. Screen Display and Control Software

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