NSC LM1281N Datasheet

LM1281
85 MHz RGB Video Amplifier System with On Screen
Display (OSD)

General Description

The LM1281 is a full feature video amplifier with OSD inputs,
all within a 28-pin package. This part is intended for use in
monitors with resolutions up to 1024 x 768. The video sec­tion of the LM1281 features three matched video amplifiers
with blanking. All of the video amplifier adjustments feature
high input impedance 0V to 4V DC controls, providing easy
interfacing to bus controlled alignment systems. The OSD
section features three TTL inputs and a DC contrast control.
The switching between the OSD and video section is con­trolled by a single TTL input. Although the OSD signals are
TTL inputs, these signals are internally processed to match
the OSD logic low level to the video black level. When ad­justing the drive controls for color balance of the video sig­nal, the color balance of the OSD display will track these
color adjustments. The LM1281 also features an internal
spot killer circuit to protect the CRT when the monitor is
turned off. For applications without OSD insertion please re­fer to the LM1205 or LM1208 data sheets.

Features

n Three wideband video amplifiers 85 MHz@−3 dB

(4 V

output)

PP

n TTL OSD inputs, 50 MHz bandwidth
n On chip blanking, outputs under 0.1 V when blanked
n High speed Video/OSD switch
n Independent drive control for each channel for color

balance

n 0V to 4V, high impedance DC contrast control with over

40 dB range

n 0V to 4V, high impedance DC drive control (0 dB to

−12 dB range)

n 0V to 4V, high impedance DC OSD contrast control with

over 40 dB range

n Capable of 7 V

bandwidth)

n Output stage directly drives most hybrid or discrete CRT

drivers

output swing (slight reduction in

PP

Applications

n High resolution RGB CRT monitors requiring OSD

capability

LM1281 85 MHz RGB Video Amplifier System with On Screen Display (OSD)

April 1999

Block and Connection Diagram

DS012355-1

FIGURE 1. Order Number LM1281N

See NS Package Number N28B

© 1999 National Semiconductor Corporation DS012355 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

Pins 6, 9, and 22 15V

Peak Video Output Source Current

(Any One Amp) Pins 18, 20, and 23 28 mA
Voltage at Any Input Pin (V
Power Dissipation (P

(Above 25˚C Derate based on

and TJ) 2.5W

θ

JA

)V

IN

)

D

≥ VIN≥ GND

CC

Thermal Resistance (θ
Junction Temperature (T

) 50˚C/W

JA

) 150˚C

J

ESD Susceptibility (Note 4) 2 kV
Storage Temperature −65˚C to +150˚C
Lead Temperature

(Soldering, 10 sec.) 265˚C

Operating Rating (Note 2)

Temperature Range: −20˚C to +70˚C
Supply Voltage (V

) 11.4V ≤ VCC≤ 12.6V

CC

DC Electrical Characteristics

See DC Test Circuit (

=

0V; V

1V unless otherwise stated

25

Figure 5

), T

A

=

25˚C; V

Symbol Parameter Conditions

I

S

R

IN

V

15l

V

15h

I

15l

I

15h

V

16l

V

16h

I

16l

I

16h

V

12

I

vid-clamp

I

vid-bias

I

out-clamp

I

out-bias

V

OL

V

OH

V

O(1V)

∆V

O(1V)

(blanked) Video Output Blanked Voltage Blank Gate On 100 500 mV (max)

V

OL

I

13,14, 26, 27, or

28

I

25

V

spot

Supply Current V
Video Input Resistance Any One Amplifier 100 kΩ
Clamp Gate Low Input Voltage Clamp Comparators On 1.2 0.8 V (max)
Clamp Gate High Input Voltage Clamp Comparators Off 1.6 2.0 V (min)
Clamp Gate Low Input Current V
Clamp Gate High Input Current V
Blank Gate Low Input Voltage Blank Gate On 1.2 0.8 V (max)
Blank Gate High Input Voltage Blank Gate Off 1.6 2.0 V (min)
Blank Gate Low Input Current V
Blank Gate High Input Current V
Reference Voltage 2.0 V
Video Input Cap Charge Current Clamp Comparators On
Video Input Cap Bias Discharge

Current
Output Clamp Cap Charge Current Clamp Comparators On
Output Clamp Cap Bias Discharge

Current
Video Output Low Voltage V
Video Output High Voltage V
Video Black Level Output Voltage V
Video ∆Black Level Output

Voltage

Contrast/Drive Control Input
Current

Cut-Off Control Input Current V
Spot Killer Voltage VCCAdjusted to Activate 10.6 11.2 V

=

=

V

CC1

12V; V

CC2

CC1+VCC2,RL

=

0V −1.5 −5.0 µA (max)

15

=

12V 0.01 1.0 µA (max)

15

=

0V −8 −11 µA (max)

16

=

12V 0.01 1.0 µA (max)

16

Clamp Comparators Off

Clamp Comparators Off

=

0V 50 100 mV (max)

25

=

10V 7.5 7 V (min)

25

=

1V 1.2 V (Note 8)

25

Between Any Two Amplifiers,

=

1V

V

25

=

V

contrast

=

0V to 4V −1.0 1.5 µA (max)

25

=

13

=

=

4V; V

14

∞

(Note 7) 95 120 mA (max)

4V; V

=

4V; V

16

Typical

(Note 5)

±

750

±

750 nA

±

750

drive

=

=

4V; V

4

Limit

(Note 6)

±

450 µA (min)

±

450 µA (min)

0V; V

750 nA

±

20

=

V

0V to 4V

Drive

−125 −500 nA (max)

±

250 mV (max)

15

Units

=

www.national.com 2

AC Electrical Characteristics

See AC Test Circuit (
4V DC for the AC test unless otherwise stated (Note 15)

Figure 6

), T

A

=

25˚C, V

Symbol Parameter Conditions

A

V max

∆A

V2V

∆A

V 0.25V

∆Drive
∆Drive

A

V match

A

V track

2V

0.25V

Video Amplifier Gain V

Contrast Attenuation@2V Ref: AVmax, V
Contrast Attenuation@0.25V Ref: AVmax, V
Drive Attenuation@2V Ref: AVmax, V
Drive Attenuation@0.25V Ref: AVmax, V
Absolute Gain Match@AVmax V

Gain Change between Amplifiers V
THD Video Amplifier Distortion V
f(−3 dB) Video Amplifier Bandwidth (Notes

11, 12)

(Video) Video Output Rise Time (Note 11) V

t

r

t

(Video) Video Output Fall Time (Note 11) V

f

V

10 kHz Video Amplifier 10 kHz Isolation V

sep

V

10 MHz Video Amplifier 10 MHz Isolation V

sep

t

(Blank) Blank Output Rise Time (Note 11) Blank Output=1V

r

t

(Blank) Blank Output Fall Time (Note 11) Blank Output=1V

f

t

(Blank) End of Blanking Propagation Delay Blank Output=1V

r-prop

t

(Blank) Start of Blanking Propagation Delay Blank Output=1V

f-prop

T

(Clamp) Back Porch Clamp Pulse Width (Note 14) 200 ns (min)

pw

CC1

=

=

V

CC2

13

V

drive

13

9)

13
O

V

13

V

O
O
O
13
13

=

12V; V

=

=

=

=

=

=
=
=

=
=

0V. Manually adjust Video Output pins 18, 20, and 23 to

4

Typical

(Note 5)

=

4V, V

=

4V, V

400 mV

IN

PP

4V 20.0 16.9 dB (min)

=

2V −6 dB

13

=

0.25V −40 dB

13

=

2V −4.5 dB

drive

=

0.25V −11 dB

drive

=

4V (Note

drive

4V to 2V (Notes 9, 10)

,f=10 kHz 1

1V

PP

4V, V

4V
4V
4V

=

3V,

drive

PP
PP
PP

10.0 7.0 V/V (min)

±

0.3 dB

±

0.2 dB

85 MHz

3.5 ns

4.5 ns

Limit

(Note 6)

4V (Note 13) −70 dB
4V (Notes 11, 13) −50 dB

PP
PP
PP
PP

8ns
14 ns
23 ns
20 ns

Units

%

www.national.com3

OSD Electrical Characteristics

See DC Test Circuit (

=

0V; V

1V unless otherwise stated

25

Figure 5

), T

A

=

25˚C; V

Symbol Parameter Conditions

V

OSDI

V

OSDh

V

4l

V

4h

I

4l

I

4h

∆V

O-OSD(1V)

V

OSD-out

∆V

OSD-out

∆V

OSD-out match

V

OSD-out track

t

(OSD S) Video to OSD Switch Time (Note

r

(OSD S) OSD to Video Switch Time (Note

t

f

(OSD S) Video to OSD Propagation Delay V

t

r-prop

t

(OSD S) OSD to Video Propagation Delay V

f-prop

t

(OSD) OSD Rise Time at VO(Note 11) V

r

t

(OSD) OSD Fall Time at VO(Note 11) V

f

t

(OSD) Starting OSD Propagation Delay V

r-prop

t

(OSD) Ending OSD Propagation Delay V

f-prop

V

10 kHz Video Feedthrough into OSD V

feed

V

10 MHz Video Feedthrough into OSD V

feed

Note 1: Absolute Maximum Rating 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 conditons.

Note 3: V
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 5: Typical specifications are specified at +25˚C 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

depends on the output load. With video output at 1V DC, the additional current through V

Note 8: Output voltage is dependent on load resistor. Test circuit uses R
Note 9: Measure gain difference between any two amplifiers. V
Note 10: ∆A

gain change between any two amplifiers with the contrast voltage (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 V
sured typical

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
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
Note 14: A minimum pulse width of 200 ns is guaranteed for a horizontal line of 15 kHz. This limit is guaranteed by design. If a lower line rate is used a longer clamp

pulse may be required.
Note 15: During the AC test the 4V DC level is the center voltage of the AC output signal. For example, if the output is 4 V

and 6V DC.
Note 16: When V

shown in

OSD Input Low Input Voltage 1.2 0.4 V (max)
OSD Input High Input Voltage 1.6 2.0 V (min)
OSD Select Low Input Voltage Video Inputs are Selected 1.2 0.8 V (max)
OSD Select High Input Voltage OSD Inputs are Selected 1.6 2.0 V (min)
OSD Select Low Input Current V
OSD Select High Input Current V
OSD ∆Black Level Output Voltage,

Difference from Video Output
OSD Output Voltage V

PP

OSD Output VPPAttenuation V
Output Match between Channels V
Output Variation between Channels V

11)

11)

supply pins 6, 9, and 22 must be externally wired together to prevent internal damage during VCCpower on/off cycles.

CC

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

V

±

0.1 dB channel tracking.

V

=

=

=

V

V

1

Figure 3

. Thus tr(OSD) is actually a fall time and tf(OSD) is actually a rise time in this condition.

0V and the video input is 0.7V, then t

2

3

=

=

V

CC1

max reference level) to the −3 dB corner frequency (f

=

10 MHz for V

IN

12V; V

CC2

=

4

=

4

=

V

25

=

V

14

=

14

=

14

=

14

=

V

1

=

V

1

=

1

=

1

=

14

=

14

=

14

=

14

=

14

=

V

1

=

14

=

V

1

and V

CC1

=

L

=

400 mV

IN

) at either 4V or 2V measured relative to an AVmax condition, V

13

sep 10 MHz

(OSD)=11ns and tf(OSD)=4 ns. The Video Output waveform will be inverted from the one

r

=

13

4V; V

=

14

0V −3.0 −5.0 µA (max)
12V 0.01 2.0 µA (min)

1V

4V, V
2V, V
4V, V
4V to 2V, V

V

2

V

2

V

2

V

2

4V; V
4V; V
4V; V
4V; V
4V; V

V

2

4V; V

V

2

CC2

390Ω.

PP

=

2V 4.5 V

Drive

=

2V 50 30

Drive

=

2V

.

=

=

=
=

=

=

with R

.

Drive

V

3

V

3

V

3

V

3
25
25
25
25
25

V

3
25

V

3

=

Drive

=

4V (Note 16)

=

4V (Note 16)

=

=

V

V

13

=

=

=

L

14

=

V

V

13

14

=

1V 4 ns

=

1V 10 ns

=

1V 6.5 ns

=

1V 9 ns

=

1V;

0V

=

1V;

0V

=

∞

, see

Figure 5’s

is 8 mA for

CC2

4V; V

2V

16

=

4V; V

Typical

(Note 5)

=

=

4V; V

Drive

±

85

±

2.0

±

3.5

4V; V

4

Limit

(Note 6)

±

175 mV (max)

4ns

11 ns

=

4V 11 ns

=

4V 12 ns

−70 dB

−60 dB

test circuit. The supply current for V

Figure 5

’s test circuit.

).

−3 dB

the signal will swing between 2V DC

PP

CC2

=

4V. For example, at A

13

=

2V.This yields the mea-

13

15

%

(pin 22) also

=

Units

PP

(min)
%
%

V

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Typical Performance Characteristics V

Attenuation vs Contrast Voltage

=

CC

12V, T

=

25˚C unless otherwise specified

A

Attenuation vs Drive Voltage

LM1281 Crosstalk vs Frequency

LM1281 Contrast vs Frequency

DS012355-2

DS012355-4

DS012355-5

DS012355-3

LM1281 Drive vs Frequency

DS012355-6

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