NSC LM2405T Datasheet
LM2405
Monolithic Triple 7 ns CRT Driver
General Description
The LM2405 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 at −14 and can drive CRT capacitive loads as well as resistive loads presented by 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
on page 5.
Features
n Rise/fall times typically 7 ns with 8 pF load
Schematic and Connection Diagram
n Output swing capability:
50 V
40 V
30 V
n Pinout designed for easy PCB layout
n 0V to 6V input range
n Stable with 0 pF–20 pF capactive loads
n Convenient TO-220 staggered lead package style
Applications
n CRT driver for 1280 x 1024 (Non-interlaced) and XGA
display resolution color monitors
n Pixel clock frequency up to 130 MHz
n Monitors using video blanking
LM2405 Monolithic Triple 7 ns CRT Driver
August 1999
=
for V
PP
for V
PP
for V
PP
80
CC
=
70
CC
=
60
CC
TabisatGND
Top View
DS012682-1
FIGURE 1. Simplified Schematic Diagram (One
Channel)
© 1999 National Semiconductor Corporation DS012682 www.national.com
Order Number LM2405T
DS012682-2
Absolute Maximum Ratings (Notes 1, 3)
Supply Voltage (V
Bias Voltage (V
Input Voltage (V
Storage Temperature Range
) −65˚C to +150˚C
(T
STG
Lead Temperature
(Soldering,
) +90V
CC
) +16V
BB
) −0.5V to V
IN
<
10 sec.) 300˚C
BIAS
+ 0.5V
Operating Ranges (Note 2)
V
CC
V
BB
V
IN
Case Temperature (T
Do not operate the part without a heat sink.
) −20˚C to +100˚C
CASE
+60V to +85V
+8V to +15V
0V to +6V
ESD Tolerance 2 kV
Electrical Characteristics
Unless otherwise noted: V
=
T
25˚C.
A
CC
=
+80V, V
Symbol Parameter Conditions
I
I
V
A
∆A
CC
BB
OUT
V
V
Supply Current Per Channel, No Output Load 18 30 mA
Bias Current 38 mA
DC Output Voltage No Input Signal 47 50 53 V
DC Voltage Gain No Input Signal −12 −14 −16
Gain Matching No Input Signal (Note 4) 1.0 dB
LE Linearity Error No Input Signal (Notes 4, 5) 8
t
R
t
F
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
Rise Time 10%to 90
Fall Time 90%to 10
R,tF
=
+12V, V
BB
1 ns.
IN
<
%
%
=
+ 1.3V to V
=
+2.6V (at LM2405 input pins), C
IN
Min Typical Max
=
+3.9V.
IN
=
8 pF, Output=40 V
L
LM2405
at 1 MHz,
PP
Units
7ns
5.5 ns
DC
%
AC Test Circuit
Note: 8 pF is total load plus parasitic capacitance.
Note: Adjust Vtest for +2.6V DC at LM2405 input pins. See “Input Resistance” section of Application Hints.
FIGURE 2. Test Circuit (One Channel)
Figure 2
LM2405. This circuit is designed to allow testing of the
LM2405 in a 50Ω environment, such as a pulse generator,
oscilloscope or network analyzer. The 4950Ω resistor at the
output forms a 100:1 voltage divider when connected to a
50Ω load.
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shows a typical test circuit for evaluation of the
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AC Test Circuit (Continued)
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FIGURE 6. Pulse Response
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FIGURE 3. V
FIGURE 4. Power Dissipation vs V
OUT
vs V
IN
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CC
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FIGURE 5. Large Signal Frequency Response
Theory of Operation
The LM2405 is a high voltage monolithic triple CRT driver
suitable for SVGA and XGA display applications. The
LM2405 features +80V operation and low power dissipation.
The part is housed in the industry standard 11-lead TO-220
molded plastic power package.
The circuit diagram of the LM2405 is shown in
Figure 1
.A
PNP emitter follower, Q5, provides input buffering. Q1 and
Q2 form a fixed gain cascode amplifier, with a gain of −14.
Emitter followers Q3 and Q4 isolate the high output impedance of the amplifier from the capacitance of the CRT cathode, and make the circuit relative insensitive to load capacitance. Q6 provides biasing to the output emitter follower
stage to reduce crossover distortion at low signal levels.
Figure 2
shows a typical test circuit for evaluation of the
LM2405. This circuit is designed to allow testing of the
LM2405 in a 50Ω environment, such as a pulse generator
and a scope, or a network analyzer. In this test circuit, two
low inductance resistors in series totaling 4.95 kΩ form a
100:1 wideband low capacitance probe when connected to a
50Ω cable and load. The input signal from the generator is
AC coupled to the base of Q5.
Application Hints
INTRODUCTION
National Semiconductor is committed to providing application information that assists our customers in obtaining the
best performance possible from our products. The following
information is provided in order to support this commitment.
The reader should be aware that the optimization of performance was done using a specific printed circuit board designed at National. Variations in performance can be realized
due to physical changes in the printed circuit board and the
application. Therefore, the designer should be aware that
component value changes may be required in order to optimize performance in a given application. The values shown
in this document can be used as a starting point for evaluation purposes. When working with high bandwidth circuits,
good layout practices are also critical to achieving maximum
performance.
POWER SUPPLY BYPASS
Since the LM2405 is a wide bandwidth amplifier, proper
power supply bypassing is critical for optimum performance.
Improper power supply bypassing can result in large overshoot, ringing and oscillation. A 0.01 µF capacitor should be
connected from the supply pin, V
, to ground, as close to
CC
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