9

LT1203/LT1205

WORKSTATION

OUTPUT

LT1203/05 • F02a

Figure 2a. Workstation and RGB MUX Output

LT1203/05 • F02b

Figure 2b. RGB MUX Output Switched to Ground

After One Pixel

S

APPLICATI

I FOR ATIO

FREQUENCY (MHz)

1

–2

–1

0

1

2

10

100

1000

LT1203/05 • F04

–3

–4

3

4

G

R, B

Input Expansion

The output impedance of the LT1203/LT1205 is typically

20

Ω when enabled and 10MΩ when disabled or not

selected. This high disabled output impedance allows the

output of many LT1205s to be shorted together to form

large crosspoint arrays. With their outputs shorted to-

gether, shoot-through current is low because the “on”

channel is disabled before the “off” channel is activated.

ENABLE

IC #1

Timing and Supply Current Waveforms

ENABLE

IC #2

1V/DIV

10mA/DIV

5V/DIV

5V/DIV

LT1203/05 • AI04

Four LT1205s are used in Figure 5 to form a 16-to-1

multiplexer which is very space efficient and uses only six

SO packages. In this application 15 switches are turned off

and only one is active. An attenuator is formed by the 15

deselected switches and the active device which has an

Figure 4. RGB MUX Frequency Response of

Demonstration Board #041

RGB MUX

OUTPUT

WORKSTATION

OUTPUT

RGB MUX

OUTPUT

Demonstration Board

A Demonstration Board (#041) of the RGB MUX in Figure

1 has been fabricated and its layout is shown in Figure 3.

The small-signal bandwidth of the RGB MUX is set by the

bandwidth of the LT1260. The stray capacitance of the

– 3dB bandwidth to about 95MHz. The bandwidth can be

improved by about 20% using the through-hole LT1260

and components. A frequency response plot in Figure 4

shows that the R, G, and B amplifiers have slightly

different frequency responses. The difference in the G

amplifier is due to different output trace routing to

feedback resistor R13.