LT1675-1 データシートの表示（PDF） - Linear Technology
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LT1675-1 Datasheet PDF : 16 Pages
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LT1675/LT1675-1
TYPICAL APPLICATION
NTSC-Related Color Bar Generator
5V
74ACT04
CLOCK IS
SUBCARRIER × 4
DIVIDED BY 91
OR 157.343kHz 5V
COMPOSITE
BLANKING
CLR ENP ENT
CLK
QA
A
74LS163
B
QB
C
D
QC
LOAD
6.04k B
+1
1k
6.04k
R
+1
1k
6.04k G
+1
1k
+1
–5V
+1
LT1675
V+
75Ω CABLE
+2
VOUT BLUE
75Ω
75Ω CABLE
+2
VOUT RED
75Ω
75Ω CABLE
+2
VOUT GREEN
75Ω
V–
0.714V
B
0
10k
–0.285V
+1
640Ω
SELECT
ENABLE
0.714V
R
0
0.714V
G
COMPOSITE
SYNC
1675 TA04
0
An RGB color bar test pattern is easily generated by
dividing down a suitable clock. To form a stable pattern,
the clock must be synchronous with the horizontal scan
rate. Four times subcarrier, or 14.318MHz, is a readily
available frequency, which when divided by 91, gives
157.343KHz. Dividing this signal by two, four and eight,
gives the blue, red and green signals, respectively. This
timing gives eight bars including white and black that fill
the 52.6µs active video time. The digital signals are run
through a 74ACT04 inverter because the CMOS output
swings rail-to-rail. The inverter output is scaled to make
video (0.714V peak, for NTSC-related RGB). The LT1675
drives the cable and adds sync to the RGB signals by
switching in –0.286V. If no sync is required, this voltage
can be set to zero and composite blanking can be used to
drive the select pin of the LT1675 in order to provide a
more precise blanking level.
RELATED PARTS
PART NUMBER
LT6555
LT1203/LT1205
LT1204
LT1260
LT1398/LT1399
DESCRIPTION
650 MHz RGB Multiplexing Amplifier
150MHz Video MUX
4-Input Video MUX with 75MHz Current Feedback Amp
Low Cost Dual and Triple 130MHz Current Feedback Amp
with Shutdown
Low Cost Dual and Triple 300MHz Current Feedback Amp
with Shutdown
16 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
COMMENTS
2200V/µs Slew Rate, 2:1 Input MUX
2-Input and 4-Input, 90dB Channel Separation, Wide Supply Range
Drives Cables, Adjustable Gain, 90dB Channel Separation
Drives Cables, Wide Supply Range, 0µA Shutdown Current
Performance Upgrade for the LT1259/LT1260
16751fb
LT/LT 0605 REV B • PRINTED IN USA
© LINEAR TECHNOLOGY CORPORATION 1998
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