NSC LM2438T Datasheet

LM2438
Monolithic Triple 13.5 ns CRT Driver

LM2438 Monolithic Triple 13.5 ns CRT Driver

August 1999

General Description

The LM2438 is an integrated high voltage CRT driver circuit
designed for use in color monitor applications. The IC con­tains three high input impedance, wide band amplifiers
which directly drivethe RGB cathodes of a CRT. Each chan­nel has its gain internally set to −14 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 Thermal Considerations
section.

Schematic and Connection Diagrams

DS101043-1

FIGURE 1. Simplified Schematic Diagram

(One Channel)

Features

n Well matched with LM1279 video preamp
n 0V to 5V input range
n Stable with 0–20 pF capacitive loads and inductive

peaking networks

n Convenient TO-220 staggered lead package style
n Standard LM243X Family Pinout which is designed for

easy PCB layout

Applications

n 1024 x 768 displays up to 60 Hz refresh
n Pixel clock frequencies up to 60 MHz
n Monitors using video blanking

DS101043-2

Note: TabisatGND

Top View

Order Number LM2438T

© 1999 National Semiconductor Corporation DS101043 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
Bias Voltage (V
Input Voltage (V
Storage Temperature Range (T

) +90V

CC

) +16V

BB

) 0Vto6V

IN

) −65˚C to +150˚C

STG

Lead Temperature

<

(Soldering,

10 sec.) 300˚C

ESD Tolerance, Human Body Model 2 kV

Machine Model 250V

Operating Ranges (Note 2)

V

CC

V

BB

V

IN

V

OUT

+60V to +85V

+8V to +15V

+0V to +5V

+15V to +75V
Case Temperature −20˚C to +100˚C
Do not operate the part without a heat sink.

Electrical Characteristics

(See

Figure 2

Unless otherwise noted: V

DC Tests: VIN= 2.8 VDC;
AC Tests: Output = 40 V

for Test Circuit)

Symbol Parameter Conditions

I

I
V
A
∆A

CC

BB

OUT
V

Supply Current All Three Channels, No AC Input

Bias Current All Three Channels 11 mA
DC Output Voltage No AC Input Signal, VIN= 1.35V 62 65 68 V
DC Voltage Gain No AC Input Signal −12 −14 −16
Gain Matching (Note 4), No AC Input Signal 1.0 dB

V

LE Linearity Error (Notes 4, 5), No AC Input Signal 8
t

R

t

F

Rise Time (Note 6), 10%to 90
Fall Time (Note 6), 90%to 10

OS Overshoot (Note 6) 5

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
Note 6: Input from signal generator: t

= +80V, VBB= +12V, CL= 8 pF, TC= 50˚C;

CC

(25V–65V) at 1 MHz.

PP

Signal, No Output Load

%
%

= 1.0V to VIN= 4.6V.

1 ns.

IN

r,tf

<

LM2438

Min Typical Max

18 mA

13.9 ns

14.2 ns

Units

DC

%

%

AC Test Circuit

Note: 8 pF load includes parasitic capacitance.

FIGURE 2. Test Circuit (One Channel)

Figure 2

shows a typical test circuit for evaluation of the LM2438. This circuit is designed to allow testing of the LM2438 in a 50Ω
environment without the use of an expensive FET probe. The two 2490Ω resistors form a 200:1 divider with the 50Ω 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 2490Ω resistors to achieve flat frequency response.

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DS101043-3

Typical Performance Characteristics (V

(25V−65V), Test Circuit -

Figure 2

unless otherwise specified)

= +80 VDC,VBB= +12 VDC,CL= 8 pF, V

CC

OUT

=40V

PP

FIGURE 3. V

OUT

vs V

IN

FIGURE 4. Speed vs Temp.

DS101043-4

DS101043-5

DS101043-7

FIGURE 6. Power Dissipation vs Frequency

DS101043-8

FIGURE 7. Speed vs Offset

DS101043-6

FIGURE 5. LM2438 Pulse Response

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Typical Performance Characteristics (V

(25V−65V), Test Circuit -

Figure 2

unless otherwise specified) (Continued)

FIGURE 8. Speed vs Load Capacitance

for Various Inductances

= +80 VDC,VBB= +12 VDC,CL= 8 pF, V

CC

DS101043-9

OUT

=40V

PP

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