LM2421
Monolithic Triple Channel HDTV Driver
General Description
The LM2421 is an integrated high voltage CRT driver circuit
designed for use in HDTV applications. The IC contains
three high input impedance, wide band amplifiers which
directly drive the RGB cathodes of a CRT. Each channel has
its gain internally set to -42 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 11-lead TO-220
molded plastic power package. See Thermal Considerations
section.
Features
n
0V to 5V input range
n
Stable with 020 pF capacitive loads and inductive
peaking networks
n
Convenient TO-220 staggered lead package style
n
Maintains standard LM240X Family pinout which is
designed for easy PCB layout
Applications
n
AC coupled HDTV applications using the 1080i and
720p formats as well as standard NTSC and PAL
formats.
Schematic and Connection Diagrams
DS200233-1
FIGURE 1. Simplified Schematic Diagram
(One Channel)
DS200233-2
Note: Tab is at GND
Top View
Order Number LM2421TA
November 2001
LM2421
Monolithic
T
riple
Channel
HDTV
Driver
2001 National Semiconductor Corporation
DS200233
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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
)
+155V
Bias Voltage (V
BB
)
+15V
Input Voltage (V
IN
)
-0.5V to V
BB
+0.5V
Storage Temperature Range (T
STG
)
-65C to +150C
Lead Temperature
(Soldering,
<
10 sec.)
300C
ESD Tolerance, Human Body Model
2kV
Machine Model
200V
Junction Temperature
150C
JC
(typ)
2.8C/W
Operating Ranges
(Note 2)
V
CC
+130V to +150V
V
BB
+7V to +13V
V
IN
+1V to +5V
V
OUT
+16V to +135V
Do not operate the part without a heat sink.
Electrical Characteristics
(See
Figure 2 for Test Circuit)
Unless otherwise noted: V
CC
= +145V, V
BB
= +8V, C
L
= 8 pF, T
C
= 50C
DC Tests: V
IN
= 2.8VDC
AC Tests: Output = 100V
PP
(32V - 132V) at 1MHz
Symbol
Parameter
Conditions
LM2421
Units
Min
Typical
Max
I
CC
Supply Current
All Three Channels, No Input Signal,
No Output Load
43
55
mA
I
BB
Bias Current
All Three Channels
29
40
mA
V
OUT
DC Output Voltage
No AC Input Signal
78
82
86
V
DC
A
V
DC Voltage Gain
No AC Input Signal
-38
-42
-46
A
V
Gain Matching
(Note 4), No AC Input Signal
1.0
dB
LE
Linearity Error
(Notes 4, 5), No AC Input Signal
8
%
t
R
Rise Time
(Note 6), 10% to 90%
11
ns
t
F
Fall Time
(Note 6), 90% to 10%
13
ns
OS
Overshoot
(Note 6)
2
%
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. Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. 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
= 1.8V to V
IN
= 3.8V.
Note 6: Input from signal generator: t
r
, t
f
<
1 ns.
LM2421
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2
AC Test Circuit
Figure 2 shows a typical test circuit for evaluation of the LM2421. This circuit is designed to allow testing of the LM2421 in a 50
environment without the use of an expensive FET probe. The two 4990
resistors form a 400:1 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 4990
resistors to achieve flat frequency response.
DS200233-3
Note: 8 pF load includes parasitic capacitance.
FIGURE 2. Test Circuit (One Channel)
LM2421
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3
Typical Performance Characteristics
(V
CC
= +145V
DC
, V
BB
= +8V
DC
, C
L
= 8pF, V
OUT
=
100V
PP
(32V-132V), Test Circuit -
Figure 2 unless otherwise specified)
DS200233-4
FIGURE 3. V
OUT
vs V
IN
DS200233-5
FIGURE 4. Speed vs Temp.
DS200233-6
FIGURE 5. LM2421 Pulse Response
DS200233-7
FIGURE 6. Power Dissipation vs Frequency
DS200233-8
FIGURE 7. Speed vs Offset
DS200233-9
FIGURE 8. Speed vs Load Capacitance
LM2421
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4
Typical Performance
Characteristics
(V
CC
= +145V
DC
, V
BB
= +8V
DC
,
C
L
= 8pF, V
OUT
= 100V
PP
(32V-132V), Test Circuit -
Figure
2 unless otherwise specified) (Continued)
DS200233-16
FIGURE 9. Power Derating Curve
LM2421
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5
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