LT6551 Linear Technology Corporation, LT6551 Datasheet - Page 14

• Manufacturer Part Number: LT6551
• Description: 3.3v Triple And Quad Video Amplifiers
• Manufacturer: Linear Technology Corporation

LT6550/LT6551
Consumer products require generation of YP
nance/chrominance component signals, often from RGB
source content. The YP
and two weighted color difference signals at baseband.
Even with their fixed internal gain resistors, two LT6550s
connected as shown easily implement the required con-
version matrix equations. The Y channel is a weighted
average of the 2X amplified RGB signals and with the
feedback connection of the Y channel output in the second
LT6550 back to the gain-resistor common pin, an implicit
Y subtraction is performed for the chroma channels and
TYPICAL APPLICATIO
14
R
G
B
75Ω
75Ω
75Ω
B
P
R
format has a luminance signal
1
2
3
LT6550
4
450Ω
450Ω
450Ω
U
Y = 0.299R + 0.587G + 0.114B
P
3.3V
B
= 0.565(B – Y)
RGB to YP
10
+
+
+
–
–
–
450Ω
450Ω
450Ω
–3.3V
B
5
P
B
R
P
9
8
7
R
1070Ω
2940Ω
lumi-
549Ω
Component-Video Conversion
the desired unity gain is produced for the Y-channel. The
necessary scaling of the color-difference signals is per-
formed passively by their respective output termination
resistor networks. Since this circuit naturally produces
bipolar chroma signals (±0.35V at the cable load) regard-
less of RGB offset, the simplest implementation is to
power the circuit with ±3.3V split supplies. With an avail-
able output swing of about 5.6V for this supply configura-
tion, the circuit handles video with composite syncs and/
or various offsets without difficulty.
1
2
3
P
f
3dB
LT6550
R
= 0.713(R – Y)
≈ 44MHz
4
450Ω
450Ω
450Ω
3.3V
10
–
+
–
+
–
+
450Ω
450Ω
450Ω
–3.3V
5
9
8
7
105Ω
133Ω
75Ω
261Ω
174Ω
6550/51 TAO3
P
Y
P
R
B
65501fa