AD8115AST datasheet(20/32 Pages) AD

20 / 32 page

AD8114/AD8115

Rev. B | Page 20 of 32

of 2 that eliminates the need for a gain-of-2 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

creating crosspoint arrays of dimensions larger than 16 × 16.

Various features, such as output disable, chip enable, and gain-

of-1 and gain-of-2 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 of (unity gain and

gain-of-2) 8 × 8 video crosspoint switches, or with the AD8110

and AD8111, a pair of (unity gain and gain-of-2) 16 × 8 video

crosspoint switches.

The first consideration in constructing a larger crosspoint is to

determine the minimum number of devices 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

availability 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 48 illustrates this concept for a 32 × 32

crosspoint array that uses four AD8114s or AD8115s.

AD8114

AD8115

AD8114

AD8115

AD8114

AD8115

AD8114

AD8115

RTERM

IN 00–15

RTERM

IN 16–31

Figure 48. 32 × 32 Crosspoint Array Using AD8114 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-OR’ed together in pairs. The output from only one of

a wire-OR’ed pair should be enabled at any given time. The

device programming software must be properly written to cause

this to happen.

AD8115AST датащи(PDF) 20 Page - Analog Devices

AD8115AST датащи(HTML) 20 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

датащи скачать

ссылки URL