LM2445
Monolithic Triple 7.5 ns CRT Driver
General Description
The LM2445 is an integrated high voltage CRT driver circuit
designed for use in color monitor applications. The IC con-
tains three high input impedance, wide band amplifiers
which directly drive the RGB cathodes of a CRT. Each
channel has its gain internally set to -20 and can drive CRT
capacitive loads as well as resistive loads present in other
applications, limited only by the package's power dissipation.
The IC is packaged in an industry standard 9-lead TO-220
molded plastic power package. See the Thermal Consider-
ations section for more information.
Features
n
Higher gain to match LM126X CMOS preamplifiers
n
0V to 3.75V input range
n
Stable with 020 pF capacitive loads and inductive
peaking networks
n
Convenient TO-220 staggered lead package style
n
Maintains standard LM243X Family pinout which is
designed for easy PCB layout
Applications
n
1024 x 768 displays up to 85 Hz refresh
n
Pixel clock frequencies up to 95 MHz
n
Monitors using video blanking
Schematic Diagram
20063701
FIGURE 1. Simplified Schematic Diagram
(One Channel)
March 2003
LM2445
Monolithic
T
riple
7.5
ns
CRT
Driver
2003 National Semiconductor Corporation
DS200637
www.national.com
Absolute Maximum Ratings
(Notes 1,
3)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
)
+90V
Bias Voltage (V
BB
)
+16V
Input Voltage (V
IN
)
0V to 4.5V
Storage Temperature Range (T
STG
)
-65C to +150C
Lead Temperature
(Soldering,
<
10 sec.)
300C
ESD Tolerance, Human Body
Model
2 kV
Machine Model
250V
Operating Ranges
(Note 2)
V
CC
+60V to +85V
V
BB
+8V to +15V
V
IN
+0V to +3.75V
V
OUT
+15V to +75V
Case Temperature
-20C to +100C
Do not operate the part without a heat sink.
Electrical Characteristics
(See Figure 2 for Test Circuit) Unless otherwise noted: V
CC
= +80V, V
BB
= +12V, C
L
= 8 pF, T
C
= 50C DC Tests: V
IN
=
2.25VDC AC Tests: Output = 40V
PP
(25V - 65V) at 1MHz
Symbol
Parameter
Conditions
LM2445
Units
Min
Typical
Max
I
CC
Supply Current
All Three Channels, No Input Signal,
No Output Load
30
mA
I
BB
Bias Current
All Three Channels
18
mA
V
OUT
DC Output Voltage
No AC Input Signal, V
IN
= 1.25V
62
65
68
V
DC
A
V
DC Voltage Gain
No AC Input Signal
-18
-20
-22
A
V
Gain Matching
(Note 4), No AC Input Signal
1.0
dB
LE
Linearity Error
(Notes 4, 5), No AC Input Signal
5
%
t
R
Rise Time
(Note 6), 10% to 90%
7.5
ns
t
F
Fall Time
(Note 6), 90% to 10%
8
ns
OS
Overshoot
(Note 6)
1
%
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
change when the device is not operated under the listed test conditions.
Note 3: All voltages are measured with respect to GND, unless otherwise specified.
Note 4: Calculated value from Voltage Gain test on each channel.
Note 5: Linearity Error is the variation in dc gain from V
IN
= 1.0V to V
IN
= 3.5V.
Note 6: Input from signal generator: t
r
, t
f
<
1 ns.
LM2445
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3
AC Test Circuit
Figure 2 shows a typical test circuit for evaluation of the LM2445. This circuit is designed to allow testing of the LM2445 in a 50
environment without the use of an expensive FET probe. The two 2490
resistors form a 200:1 divider with the 50 resistor and
the oscilloscope. A test point is included for easy use of an oscilloscope probe. The compensation capacitor is used to
compensate the stray capacitance of the two 2490
resistors to achieve flat frequency response.
20063703
Note: 8 pF load includes parasitic capacitance.
FIGURE 2. Test Circuit (One Channel)
LM2445
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4
Typical Performance Characteristics
(V
CC
= +80 V
DC
, V
BB
= +12 V
DC
, C
L
= 8 pF, V
OUT
= 40 V
PP
(25V-65V), Test Circuit - Figure 2 unless otherwise specified)
20063704
FIGURE 3. V
OUT
vs V
IN
20063705
FIGURE 4. Speed vs Temp.
20063706
FIGURE 5. LM2445 Pulse Response
20063707
FIGURE 6. Power Dissipation vs Frequency
20063708
FIGURE 7. Speed vs Offset
20063709
FIGURE 8. Speed vs Load Capacitance
LM2445
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5
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