14

LT1203/LT1205

S

APPLICATI

I FOR ATIO

those used in the 16-to-1 crosspoint with one additional

suggestion: Surround the LT1205 output traces by ground

plane and route them away from the (–) inputs of the

other three LT1254s.

Each pair of logic inputs labeled Select Logic Output is

used to select a particular output. The truth table is used

to select the desired input and is applied to each pair of

logic inputs. For example, to route Channel 1 Input to

Output 3, the 4th pair of logic inputs labeled Select Logic

Output 3 is coded A = Low and B = High. To route

Channel 3 Input to all outputs, set all eight logic inputs

High. Channel 3 is the default input with all logic inputs

open. To shut off all channels a pair of LT1259s can be

substituted for the LT1254. The LT1259 is a dual current

feedback amplifier with a shutdown pin that reduces the

supply current to 0

µA.

Response of All Four Inputs for the 4

× 4 Crosspoint

FREQUENCY (MHz)

1

2

0

–2

–4

–6

–8

10

100

LT1203/05 • AI08

200

LT1203/05 • AI10

CHANNEL 0 = 1V

CHANNEL 2 = 0V

4

× 4 Crosspoint, Switching Channel 0 to Channel 2

INPUT A

OF SELECT

LOGIC

OUTPUT 0

5V

0V

4

× 4 Crosspoint, All Hostile Rejection

FREQUENCY (MHz)

1

–120

–100

–80

–60

–40

10

100

LT1203/05 • AI09