LT1205 Linear Technology Corporation, LT1205 Datasheet - Page 9

• Manufacturer Part Number: LT1205
• Description: 150mhz Video Multiplexers
• Manufacturer: Linear Technology Corporation

A
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
– 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.
WORKSTATION
WORKSTATION
PPLICATI
RGB MUX
RGB MUX
OUTPUT
OUTPUT
OUTPUT
OUTPUT
Figure 2b. RGB MUX Output Switched to Ground
After One Pixel
Figure 2a. Workstation and RGB MUX Output
O
U
S
I FOR ATIO
U
F
W
and R
G
restricts the
LT1203/05 • F02b
LT1203/05 • F02a
U
Input Expansion
The output impedance of the LT1203/LT1205 is typically
20
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.
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
10mA/DIV
ENABLE
ENABLE
1V/DIV
IC #1
IC #2
V
OUT
I
S
when enabled and 10M
Figure 4. RGB MUX Frequency Response of
Demonstration Board #041
–1
–2
–3
–4
Timing and Supply Current Waveforms
4
3
2
1
0
1
V
R
R
S
L
F
= R
= ±15V
= 150
G
= 1.3k
FREQUENCY (MHz)
10
G
R, B
LT1203/LT1205
100
when disabled or not
LT1203/05 • F04
1000
LT1203/05 • AI04
5V/DIV
5V/DIV
9