LM1208
130 MHz/85 MHz RGB Video Amplifier System with
Blanking
General Description
The LM1208 is a very high frequency video amplifier system
intended for use in high resolution RGB monitor applications.
In addition to the three matched video amplifiers, the
LM1208 contains three gated single ended input black level
clamp comparators for brightness control, three matched DC
controlled attenuators for contrast control, and three DC
controlled sub-contrast attenuators providing independent
full range gain control in each channel for wide range white
balance. All DC control inputs offer high input impedance
and an operation range from 0V to 4V for easy interface to
bus controlled alignment systems. The LM1208 also con-
tains a blanking circuit which clamps the video output volt-
age during blanking to within 0.1V above ground. This fea-
ture provides blanking capability at the cathodes of the CRT.
A spot killer is provided for CRT phosphor protection during
power-down.
Features
n
Three wideband video amplifiers 130 MHz (LM1208)
@
-3 dB (4 V
PP
output)
n
Matched (
0.1 dB or 1.2%) attenuators for contrast
control
n
ESD susceptibility above 3 kV
n
Three externally gated single ended input comparators
for cutoff and brightness control
n
0V to 4V, high input impedance DC contrast control
(
>
40 dB range)
n
0V to 4V, high input impedance DC full range gain
control (Drive) for each video channel (
>
40 dB range)
n
Spot killer, blanks output when V
CC
<
10.6V
n
Capable of 7 V
PP
output swing (slight reduction in
bandwidth)
n
Output stage blanking
n
Output stage directly drives most hybrid or discrete CRT
drivers
Applications
n
High resolution RGB CRT monitors
n
Video AGC amplifiers
n
Wideband amplifiers with gain and DC offset controls
n
Interface amplifiers for LCD or CCD systems
Block and Connection Diagram
DS100083-1
FIGURE 1.
Order Number LM1208 See NS Package Number N28B
OBSOLETE
October 2001
LM1208
130
MHz/85
MHz
RGB
V
ideo
Amplifier
System
with
Blanking
2001 National Semiconductor Corporation
DS100083
www.national.com
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
)
Pins 3, 11, 22, 23, 25 (Note 3)
15V
Peak Video Output Source Current
(Any One Amp) Pins 17, 20 or 26
28 mA
Voltage at Any Input Pin (V
IN
)
V
CC
V
IN
GND
Power Dissipation (P
D
)
(Above 25C Derate Based on
JA
and T
J
)
2.5W
Thermal Resistance (
JA
)
50C/W
Junction Temperature (T
J
)
150C
ESD Susceptibility (Note 4)
3 kV
ESD Machine Model (Note 15)
350V
Storage Temperature
-65C to 150C
Lead Temperature
(Soldering, 10 sec.)
265C
Operating Ratings
(Note 2)
Temperature Range
-20C to 80C
Supply Voltage (V
CC
)
10.8V
V
CC
13.2V
DC Electrical Characteristics
See DC Test Circuit
(Figure 2), T
A
= 25C; V
CC1
= V
CC2
= 12V. V
12
= 4V; V
14
= 0V; V
cut-off
= 1.0V; V
13
= 4V; V
drive
= 4V un-
less otherwise stated.
Symbol
Parameter
Conditions
Typical
Limit
Units
(Note 5)
(Note 6)
I
S
Supply Current
V
CC1
+ V
CC2
, R
L
=
(Note 7)
90
105
mA (max)
V
4, 6, 9
Video Amplifier Input Bias Voltage
2.8
V
R
IN
Video Input Resistance
Any One Amplifier
20
k
V
14l
Clamp Gate Low Input Voltage
Clamp Comparators On
1.2
0.8
V (max)
V
14h
Clamp Gate High Input Voltage
Clamp Comparators Off
1.6
2.0
V (min)
I
14l
Clamp Gate Low Input Current
V
14
= 0V
-1
-5
A (max)
I
14h
Clamp Gate High Input Current
V
14
= 12V
0.01
1.0
A (max)
I
clamp
Clamp Cap Charge Current
Clamp Comparators On
750
500
A (min)
I
bias
Clamp Cap Bias Discharge Current
Clamp Comparators Off
500
nA
V
13l
Blank Gate Low Input Voltage
Blank Gate On
1.2
0.8
V (max)
V
13h
Blank Gate High Input Voltage
Blank Gate Off
1.6
2.0
V (min)
I
13l
Blank Gate Low Input Current
V
13
= 0V
-5.0
-11.0
A (max)
I
13h
Blank Gate High Input Current
V
13
= 12V
0.01
1.0
A (max)
V
OL
Video Output Low Voltage
V
cut-off
= 0V
0.15
0.5
V (max)
V
OH
Video Output High Voltage
V
cut-off
= 9V
7.5
7
V (min)
V
O(1V)
Video Black Level Output Voltage
V
cut-off
= 1V
1.0
V
(Note 8)
V
O(1V)
Video
Black Level Output Voltage
Between Any Two Amplifiers,
100
mV (max)
V
cut-off
= 1V
V
OL
(blanked)
Video Output Blanked Voltage
V
13
= 0V
35
70
mV (max)
I
12, 15, 18 or 28
Contrast/Drive Control Input Current
V
contrast
= V
drive
= 0V to 4V
-250
nA
I
16, 19 and 27
Cut-Off Control Input Current (All Inputs)
V
cut-off
= 0V to 4V
-500
nA
V
spot
Spot Killer Voltage
V
CC
Adjusted to Activate
10.4
10.8
V (max)
LM1208
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2
AC Electrical Characteristics
(Note 14)
See AC Test Circuit (
Figure 3 ) , T
A
= 25C; V
CC1
= V
CC2
= 12V. Manually adjust Video Output pins 17, 20, and 26 to 4V DC
for the AC test unless otherwise stated.
Symbol
Parameter
Conditions
Typical
Limit
Units
(Note 5)
(Note 6)
A
V max
Video Amplifier Gain
V12 = 4V, V
IN
= 635 mV
PP
7.0
6.0
V/V (min)
V
drive
= 4V
16.9
15.6
dB (min)
A
V 2V
Attenuation
@
2V
Ref: A
V
max, V12 = 2V
-6
dB
A
V 0.25V
Attenuation
@
0.25V
Ref: A
V
max, V12 = 0.25V
-40
dB
Drive
2V
Drive Attenuation
@
2V
Ref: A
V
max, V
drive
= 2V
-6
dB
Drive
0.25V
Drive Attenuation
@
0.25V
Ref: A
V
max, V
drive
= 0.25V
-40
dB
A
V match
Absolute Gain Match
@
A
V
max
V12 = 4V, V
drive
= 4V (Note 9)
0.3
dB
A
V track1
Gain Change Between Amplifiers
V12 = 4V to 2V (Note 9) (Note 10)
0.1
dB
THD
Video Amplifier Distortion
V
O
= 1 V
PP
, f = 10 kHz
1
%
f (-3 dB)
Video Amplifier Bandwidth
V12 = 4V, V
drive
= 4V,
MHz
(Note 11) (Note 12)
V
O
= 4 V
PP
t
r
(Video)
Video Output Rise Time (Note 11)
V
O
= 4 V
PP
2.8
ns
t
f
(Video)
Video Output Fall Time (Note 11)
V
O
= 4 V
PP
3.4
ns
V
sep
10 kHz
Video Amplifier 10 kHz Isolation
V12 = 4V (Note 13)
-70
dB
V
sep
10 MHz
Video Amplifier 10 MHz Isolation
V12 = 4V (Note 11) (Note 13)
-50
dB
t
r
(Blank)
Blank Output Rise Time (Note 11)
Blank Output = 1 V
PP
7
ns
t
f
(Blank)
Blank Output Fall Time (Note 11)
Blank Output = 1 V
PP
7
ns
t
pw
(Clamp)
Min. Back Porch Clamp Pulse
Width
200
ns
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Note 2: Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and
test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
Note 3: V
CC
supply pins 3, 11, 22, 23, 25 must be externally wired together to prevent internal damage during V
CC
power on/off cycles.
Note 4: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 5: Typical specifications are specified at +25C and represent the most likely parametric norm.
Note 6: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 7: The supply current specified is the quiescent current for V
CC1
and V
CC2
with R
L
=
, see
Figure 2
's test circuit. The supply current for V
CC2
(pin 23) also
depends on the output load. With video output at 1V DC, the additional current through V
CC2
is 8 mA for
Figure 2
's test circuit.
Note 8: Output voltage is dependent on load resistor. Test circuit uses R
L
= 390
.
Note 9: Measure gain difference between any two amplifiers. V
IN
= 635 mV
PP
.
Note 10:
A
V
track is a measure of the ability of any two amplifiers to track each other and quantifies the matching of the three attenuators. It is the difference in
gain change between any two amplifiers with the contrast voltage (V12) at either 4V or 2V measured relative to an A
V
max condition, V12 = 4V. For example, at A
V
max the three amplifiers' gains might be 17.1 dB, 16.9 dB and 16.8 dB and change to 11.2 dB, 10.9 dB, and 10.7 dB respectively for V12 = 2V. This yields the
measured typical
0.1 dB channel tracking.
Note 11: When measuring video amplifier bandwidth or pulse rise and fall times, a double sided full ground plane printed circuit board without socket is
recommended. Video amplifier 10 MHz isolation test also requires this printed circuit board. The reason for a double sided full ground plane PCB is that large
measurement variations occur in single sided PCBs.
Note 12: Adjust input frequency from 10 MHz (A
V
max reference level) to the -3 dB corner frequency (f
-3 dB
).
Note 13: Measure output levels of the other two undriven amplifiers relative to the driven amplifier to determine channel separation. Terminate the undriven amplifier
inputs to simulate generator loading. Repeat test at f
IN
= 10 MHz for V
sep 10 MHz
.
Note 14: During the AC tests the 4V DC level is the center voltage of the AC output signal. For example, if the output is 4 V
PP
the signal will swing between 2V DC
and 6V DC.
Note 15: Machine Model ESD test is covered by specification EIAJ IC-121-1981. A 200 pF cap is charged to the specified voltage, then discharged directly into the
IC with no external series resistor (resistance of discharge path must be under 50
).
LM1208
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3
Typical Performance Characteristics
V
CC
= 12V, T
A
= 25C unless otherwise specified
Attenuation vs Contrast Voltage
DS100083-2
Attenuation vs Drive Voltage
DS100083-3
LM1208
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4
Typical Performance Characteristics
V
CC
= 12V, T
A
= 25C unless otherwise specified (Continued)
LM1208 Crosstalk vs Frequency
DS100083-4
LM1208 Contrast vs Frequency
DS100083-5
LM1208 Drive vs Frequency
DS100083-6
LM1208
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5
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