Datasheet

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
U
S
A
O
PP
L
IC
AT
I
WU
U
I FOR ATIO
FREQUENCY (MHz)
1
–2
GAIN (dB)
–1
0
1
2
10 100 1000
LT1203/05 • F04
–3
–4
3
4
G
R, B
V
S
= ±15V
R
L
= 150
R
F
= R
G
= 1.3k
Input Expansion
The output impedance of the LT1203/LT1205 is typically
20 when enabled and 10M 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
V
OUT
1V/DIV
I
S
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
surface mount feedback resistors R
F
and R
G
restricts 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.