220V Monolithic Single Channel 37 MHz HDTV CRT
General Description
The LM2432 is a single channel high voltage CRT driver
circuit designed for use in Rear-Projection and Direct-View
HDTV applications. The IC contains a high input impedance,
wide band amplifier which can be DC coupled to a cathode
of a CRT. The amplifier has its gain internally set to −53 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 a staggered 7-lead TO-220 molded
plastic power package designed specifically to meet high
voltage spacing requirements. See the section “Power Dissipation and Heatsink Calculation” for more information.
Pinout Diagram
37 MHz bandwith at 110VPP output swing
0V to 4V input range
Greater than 130VPP output swing capability
IK Current Output (Pin 5) for IK feedback systems
Stable with 0–20 pF capacitive loads and inductive
peaking networks
n For Rear-Projection and Direct-View DC coupled CRT
applications using up to 720p and 1080i HDTV formats
n Compatible with RGB video processors with IK feedback
for automatic cathode calibration
Schematic Diagram
Note: Tab is at GND. Pin 6 is not connected (N/C) internally.
Top View
Order Number LM2432TE
FIGURE 1. Simplified Connection and Pinout Diagram
FIGURE 2. Simplified Schematic Diagram
© 2005 National Semiconductor Corporation
LM2432 220V Monolithic Single Channel 37 MHz HDTV CRT Driver
April 2005
Absolute Maximum Ratings
Operating Ranges (Note 2)
(Notes 1,
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
+7V to +13V
0V to +4.25V
Supply Voltage (VCC)
Bias Voltage (VBB)
-0.5V to VBB+0.5V
IK Voltage (VIK)
Input Voltage (VIN)
0V to VBB+1V
+40V to VCC–5V
Case Temperature
-0.5V to +16V
Storage Temperature Range (TSTG)
+130V to +230V
See Figure 11. Derate power for
TC above 110˚C.
Do not operate the part without a heat sink.
-65˚C to +150˚C
Lead Temperature
(Soldering, < 10 sec.)
ESD Tolerance,
Human Body Model
2 kV
Machine Model
Junction Temperature
θJC (typ)
Electrical Characteristics (See Figure 3 for Test Circuit)
Unless otherwise noted: VCC = +220V, VBB = +12V, CL = 10 pF, TC = 40˚C.
DC Tests: VIN = 2.75VDC
AC Tests: Output = 110VPP (80V - 190V) at 1 MHz
Supply Current
Bias Current
DC Output Voltage
DC Output Voltage
No AC Input Signal, VIN = 1.25VDC
DC Voltage Gain
No AC Input Signal
Linearity Error
(Note 4), No AC Input Signal
Rise Time
(Note 5), 10% to 90%
(Note 5)
Fall Time
(Note 5), 90% to 10%
(Note 5)
IK Current Output Error
(Notes 6, 7)
No AC Input Signal, No Output Load
No AC Input Signal, VIN = 2.75VDC
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
Note 3: All voltages are measured with respect to GND, unless otherwise specified.
Note 4: Linearity Error is the variation in DC gain from VIN = 1.15V to VIN = 4.35V.
Note 5: Input from signal generator: tr, tf < 2 ns. Slower inputs to the LM2432 will change the transient response characteristics and reduce power dissipation.
Note 6: IKERROR = IK – IOUT, where IK is the IK current output from pin 5 (IK) and IOUT is the cathode current into pin 2 (VOUT). IK is calculated by measuring VIK
across a known resistor value between pin 5 and GND.
Note 7: Refer to the RGB Video Processor data sheet for IK leakage compensation, feedback operation, and adjustment range information.
AC Test Circuit
Note: 10pF load includes parasitic capacitance.
FIGURE 3. Test Circuit
Figure 3 shows a typical test circuit for evaluation of the LM2432. This circuit was designed to test the transient response of the
LM2432 in a 50Ω environment without the use of an expensive FET probe. On the input side, a 50Ω pulse generator output can
be AC coupled and biased with an external supply via the VADJ input. On the output side, the two 4990Ω resistors form a 400:1
divider with the 50Ω resistor and the oscilloscope. A test point can be included for easy use of an oscilloscope probe. A
compensation capacitor can be used to compensate the network to achieve a flat frequency response.
Typical Performance Characteristics
(VCC = +220V, VBB = +12V, CL = 10 pF, VOUT = 110VPP (80V
− 190V), Test Circuit - Figure 3, unless otherwise specified)
FIGURE 7. Speed vs Load Capacitance
FIGURE 8. Speed vs Offset
FIGURE 5. LM2432 Pulse Response
FIGURE 9. Speed vs Case Temperature
FIGURE 6. Bandwidth
FIGURE 10. Power Dissipation vs Frequency
FIGURE 11. Power Derating Curve
FIGURE 12. Cathode Pulse Response
Typical Performance Characteristics (VCC = +220V, VBB = +12V, CL = 10 pF, VOUT = 110VPP (80V
− 190V), Test Circuit - Figure 3, unless otherwise specified) (Continued)
cover are designed specifically for the LM2432. If another
member of the NSC DTV CRT Driver family is used, please
refer to its data sheet.
Theory of Operation
The LM2432 is a high voltage monolithic single channel CRT
driver suitable for HDTV applications. The LM2432 typically
operates with 220V and 12V power supplies. The part is
housed in a staggered 7-lead TO-220 molded plastic power
The circuit diagram of the LM2432 is shown in Figure 2. The
PNP emitter follower, Q5, provides input buffering. Q1 and
Q2 form a fixed gain cascode amplifier with resistors R1 and
R2 setting the gain at −53. Emitter followers Q3 and Q4
isolate the high output impedance of the cascode stage from
the capacitance of the CRT cathode which decreases the
sensitivity of the device to load capacitance. Q6 provides
biasing to the output emitter follower stage to reduce crossover distortion at low signal levels.
Since the LM2432 is a wide bandwidth amplifier, proper
power supply bypassing is critical for optimum performance
and for robustness against arcover. Improper power supply
bypassing can result in large overshoot, ringing or oscillation, and even arcover failure. 0.1 µF capacitors should be
connected from the supply pins, VCC and VBB, to ground
using very short traces. Additionally, a 10 µF or larger electrolytic capacitor should be connected from both supply pins
to ground reasonably close to the LM2432.
The LM2432 has an IK current output (pin 5) that produces a
replica of the actual cathode current into VOUT (pin 2). The IK
output pin is internally connected to the collector of Q4. If IK
feedback is not used in the application, the IK pin should be
connected to the same ground as pin 3 (GND). Otherwise,
the IK output can interface with a RGB video processor with
IK feedback for automatic cathode calibration. Note: During
the non-blanking period, video current levels can be as high
as several mA, which is much higher than the reference
currents (in µA range) produced during the IK measurement
interval. These high currents have the potential to produce
large voltages at the IK output pin. To avoid damage to Q4,
the IK output voltage, VIK, must not exceed +16V (VIKMAX).
Please see the section “Cathode Current Output for IK Feedback Systems” for more information on the usage and protection of the IK output.
During normal CRT operation, internal arcing may occasionally occur. This fast, high voltage, high energy pulse can
damage the LM2432 output stage since it is DC coupled to
the cathode. In a DC coupled application, an external spark
gap with an arcover voltage rating of 200 to 300VDC on the
cathode is NOT recommended. The internal CRT socket
spark gap (1 to 2 kVDC rating) can sufficiently reduce the
initial arcover voltage seen at the cathode. The output circuit
shown in Figure 13 is designed to help clamp the voltage at
the output of the LM2432 to a safe level during an arcover.
External arc protection clamp diodes, D1 and D2, should
have a fast transient response, high peak current rating, low
series impedance and low shunt capacitance. 1SS83 or
equivalent diodes like BAV21 are recommended. D1 and D2
should have short, low impedance connections to VCC and
ground respectively. The cathode of D1 should have a very
short connection to a separate VCC bypass capacitor, C3.
The ground connection of D2 and the C3 should have a
short, direct path to ground. This will significantly reduce the
high frequency voltage transients that the LM2432 would be
subjected to during an arcover.
Resistor R2, which limits the arcover current that is seen by
the diodes, should be a 1⁄2W solid carbon type resistor. R1
limits the current into the LM2432 as well as the voltage
stress at the outputs of the device and can be a 1⁄4W metal or
carbon film type resistor. Having large value resistors for R1
and R2 would be desirable, but this has the effect of increasing rise and fall times. Inductor L1 is critical to reduce the
initial high frequency voltage levels that the LM2432 would
be subjected to. The inductor will not only help protect the
device but it will also help minimize rise and fall times as well
as minimize EMI. For proper arc protection, it is important to
not omit any of the arc protection components shown in
Figure 13.
Application Hints
National Semiconductor (NSC) is committed to provide 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 NSC. Variations in performance can be realized
due to physical changes in the printed circuit board and the
application. Therefore, the designer should know 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.
The LM2432 performance is targeted for the HDTV market.
The application circuits shown in this document to optimize
performance and to protect against damage from CRT ar-
Application Hints
FIGURE 13. Recommended Application Circuit
A Practical Approach to Power Dissipation
Figure 7 shows the effect of increased load capacitance on
the speed of the device. The rise and fall time increase by
7% and 7.5%, respectively, per additional pF above 10 pF.
The power curve (Figure 10) mentioned previously shows
the LM2432 power dissipation for square wave frequencies
ranging from 1 to 50 MHz at 110VPP swing. In practice, it is
unrealistic for a TV to display average frequency content
over the entire picture exceeding 20 MHz. Therefore, it is
important to establish the worst-case picture condition under
normal viewing to give a realistic maximum power dissipation for the LM2432. Here is one approach:
A HDTV signal generator pattern that yields a practical
worst-case picture condition is a “multi-burst” pattern that
consists of a 1-to-30 MHz sine wave sweep over each of the
active lines. The power dissipated by the LM2432 as a result
of this picture condition can be approximated by taking the
average of the power between 1 to 30 MHz in Figure 10. This
average is 7W. Because a square wave input was used to
generate this power curve, a sine wave would cause the
LM2432 to dissipate slightly less power, probably about
6.7W. This is one common way to determine a practical
figure for maximum power dissipation. It is the system designer’s responsibility to establish the worst-case picture
condition for his particular application and measure dissipation under that condition to choose a proper heatsink.
Heatsink Calculation Example
Once the maximum dissipation is known, Figure 11 can be
used to determine the heatsink requirement for the LM2432.
If the 1-to-30 MHz multi-burst test described previously is
assumed to be worst-case picture condition that yields maximum dissipation, then the LM2432 will dissipate about 6.7W.
The power derating curve shows that the maximum allowed
case temperature is 120˚C when 6.7W is dissipated. If the
maximum expected ambient temperature is 65˚C, then the
maximum thermal resistance from device case-to-sink (θCS)
can be calculated:
Figure 8 shows the variation in rise and fall times when the
DC offset of the 110VPP output swing is varied between
120V and 150VDC. The rise time shows a variation of less
than 10% relative to the center data point (135VDC). The fall
time shows a variation of 14% relative to the center data
Figure 9 shows the performance of the LM2432 as a function
of case temperature. The figure shows that the rise and fall
times of the LM2432 increase by approximately 17% and
20%, respectively, as the case temperature increases from
40˚C to 90˚C. This corresponds to a speed degradation of
only 3.5% and 4.0% for every 10˚C rise in case temperature.
Worst-Case Power Dissipation
Figure 10 shows the maximum power dissipation of the
LM2432 vs. square wave frequency when the device uses
VCC of 220V and is driving a 10 pF load with 110VPP swing
alternating one pixel on, one pixel off signal. Note that the
frequency range shown in the power dissipation figure is
one-half the actual pixel frequency. The graph assumes 80%
active time (device operating at the specified frequency),
which is typical in a HDTV application. The other 20% of the
time the device is assumed to be sitting at the black level
(190V in this case). Under these worst-case condition, the
maximum power dissipated by the LM2432 is about 8.9W at
around 30 MHz. It is important to note that this power dissipation is a result of a high frequency square wave input,
which is unrealistic in practical TV applications. The bandwidth of the input source used to drive the LM2432 was over
300 MHz. Using a RGB video processor or preamplifier with
less bandwidth may cause the LM2432 to dissipate less
power than shown in Figure 10 at the same conditions.
θCS = (120˚C – 65˚C) / 6.7W = 8.2˚C/W
This example assumes a capacitive load of 10 pF and no
resistive load. The designer should note that if output swing,
VCC supply voltage, input bandwidth, or load capacitance is
increased, then the AC component of the total power dissipation will also increase.
Application Hints
back circuit in detail. For more information, please refer to
the RGB processor data sheet or contact your local National
Semiconductor Sales Office with your specific application
Tips for Reducing Power Dissipation
The following methods can be used to reduce the power
dissipated by the LM2432 in order to optimize heatsink size
and cost:
• Use a lower VCC supply voltage while maintaining sufficient operating range for cutoff, brightness, and drive
• Reduce the input bandwidth to the LM2432 while maintaining acceptable picture performance.
• Lower the maximum VPP swing while maintaining acceptable picture contrast and brightness.
• Minimize capacitive load on the LM2432 output by using
good PCB layout practices.
Feedback Topologies
RGB processors that use voltage feedback require the
LM2432 IK current to be converted to voltage via a resistor
(RIK) to ground. This IK voltage, VIK, will be fed back to the IK
input of the RGB processor through an interface circuit,
which will be AC or DC coupled depending on the processor’s IK input requirement. For proper feedback operation,
some processors may require an emitter follower to isolate
the IK input from the high impedance of the resistor. During
the closed-loop IK measurement interval, the IK input voltage will be sampled and compared with the processor’s
internal reference voltage to automatically calibrate the video
levels for the next field. The value of RIK is crucial, since it
establishes the IK voltage and consequently, the operating
point of the CRT. Once a stable operating point is established with a properly chosen resistor, this point can be
fine-tuned using the adjustment range of the processor’s
RGB cut-off and/or gain controls via the I2C-bus. After the IK
measurement interval (usually at the end of blanking), normal video will resume and high currents will flow out of the IK
output. These high video currents will produce large IK voltages across the resistor that can exceed the maximum
voltage rating for VIK. Therefore, it is recommended to use a
high-speed diode (DPROT) to clamp the LM2432 IK output to
a safe level (preferably VBB or a lower supply). If a zener
diode is used instead, it may be necessary for the RGB
processor to have IK leakage compensation for the leakage
current attributed to the zener. Lastly, it is possible to use a
single RIK resistor to set the IK voltage for all three LM2432s.
See a simplified voltage feedback interface circuit in Figure
Referring to Figure 13, there are three components (R1, R2
and L1) that can be adjusted to optimize the transient response of the application circuit. Increasing the values of R1
and R2 will slow the circuit down while decreasing overshoot. Increasing the value of L1 will speed up the circuit as
well as increase overshoot. It is very important to use inductors with very high self-resonant frequencies, preferably
above 300 MHz. Ferrite core inductors from J.W. Miller
Magnetics (part # 78FR_ _k) were used for optimizing the
performance of the device in the NSC application board. The
values shown in Figure 16 can be used as a good starting
point for the evaluation of the LM2432. Using a variable
resistor for R1 will simplify finding the value needed for
optimum performance in a given application. Once the optimum value is determined, the variable resistor can be replaced with a fixed value.
Figure 12 shows a typical cathode pulse response with an
output swing of 110VPP using a RGB video processor that
provides input speeds with 12 ns rise and fall times. Note:
The RGB processor’s sharpness feature adds emphasis
(preshoots and overshoots) to the rising and falling edges of
the input pulse, which consequently adds emphasis to the
cathode pulse response.
IK Feedback Systems
IK feedback was developed to accurately bias the CRT and
continuously calibrate it to the correct cut-off and/or drive
levels over the useful life of the CRT. RGB video processors
that use IK feedback to automatically adjust only cut-off, or
black level, are realized by a 1-point calibration system. A
few trade names for this system are Auto Kine Bias (AKB)
and Black Current Stabilization (BCS). RGB processors that
can automatically adjust both cut-off and drive, or white
level, are realized by a 2-point calibration system. This is
commonly known as Continuous Cathode Calibration
(CCC). For convenience, some 2-point RGB processors may
be programmed to 1-point operation if drive calibration is not
required. The LM2432 is compatible with both 1- and 2-point
To be compatible with various RGB processors, an interface
circuit may be needed in the feedback path between the
LM2432 IK output and the processor’s IK input. This feedback circuit depends on the RGB processor and feedback
topology (voltage or current) used. Because each processor
has its own IK input signal and topology requirements, it is
outside the scope of this data sheet to describe each feedwww.national.com
FIGURE 14. Simplified IK Interface for Voltage
Feedback Systems
RGB processors that use current feedback do not require
voltage conversion. The LM2432 IK current can be fed back
directly to the IK input of the RGB processor, although some
protection circuitry will be needed to protect the RGB processor and LM2432. During the closed-loop IK measurement interval, the voltage of the RGB processor’s IK pin will
be internally clamped, and the IK current will be sampled and
compared with the processor’s internal reference current to
calibrate the video levels. The operating point of the CRT
can be fine-tuned using the adjustment range of the proces8
voltage or current signal to the RGB processor. However,
each LM2432 IK output should have its own protection diode
on its PCB.
sor’s RGB cut-off and/or gain controls via the I2C-bus. When
normal video resumes, a protection element should shunt
high video current away from the IK input of the RGB processor. Since the processor’s IK pin is not clamped during
normal video, VIK of the LM2432 must not exceed +16V
(VIKMAX). A properly chosen high speed, low-leakage zener
diode (DPROT) can be used to protect both the RGB processor input and LM2432 IK output in this case. Again, it may be
necessary for the RGB processor to have IK leakage compensation for the leakage current attributed to the zener. See
a simplified current feedback interface circuit in Figure 15.
For optimum performance, an adequate ground plane, isolation between channels, good supply bypassing and minimizing unwanted feedback are necessary. Also, the length of
the signal traces from the preamplifier to the LM2432 and
from the LM2432 to the CRT cathode should be as short as
possible. The following references are recommended:
Ott, Henry W., “Noise Reduction Techniques in Electronic
Systems”, John Wiley & Sons, New York, 1976.
“Video Amplifier Design for Computer Monitors”, National
Semiconductor Application Note 1013.
Pease, Robert A., “Troubleshooting Analog Circuits”,
Butterworth-Heinemann, 1991.
Because of its high small signal bandwidth, the part may
oscillate in a TV if feedback occurs around the video channel
through the chassis wiring. To prevent this, leads to the video
amplifier input circuit should be shielded, and input circuit
wiring should be spaced as far as possible from output circuit
The high bandwidth, large swing capability, and simple application make the LM2432 ideal for Rear-Projection and
Direct-View HDTV CRT applications. The IK output can be
made compatible with any RGB video processor with IK
feedback. If the IK output is not used in the application, it
should be connected to the same ground as pin 3 (GND).
See the section “Cathode Current Output for IK Feedback
Systems” for more information.
FIGURE 15. Simplified IK Interface for Current
Feedback Systems
LM2432 IK Output and Protection Requirements
The LM2432 IK output sources a copy of the actual cathode
current to the interface circuit during the closed-loop IK
measurement interval and during normal video when the IK
feedback loop is opened. Because the cathode current during normal video is much higher than the low current being
measured during the measurement interval, VIK may exceed
it’s maximum rating. To protect and prevent improper operation of the LM2432, VIK must be maintained within the range
specified in the Section Operating Ranges .
Figure 16 and Figure 17 show the schematic and PCB layout
for the NSC demonstration neck board for a typical RearProjection HDTV application with IK feedback. This single
channel neck board could be used for all three channels,
since each neck board receives video-related signals directly
from the RGB mainboard. The power supplies are daisychained between each channel using inboard and outboard
connectors J6 and J7. This board provides a good example
of a layout that can be used as a guide for future layouts.
Samples of the NSC demonstration neck board are available
upon request to your local National Semiconductor Sales
Input Video Interface
On the RGB mainboard, the video output of the RGB processor is buffered with a PNP transistor to drive the video
through flat cabling to the NSC neck board. The cabling from
the mainboard plugs into the neck board at connector J8 to
supply it with video, IK, GND, and other signals. Between the
video input (pin 3) of J8 and VIN (pin 7) of the LM2432 is
another buffer stage consisting of two NPN transistors. Both
NPN transistors drop the video levels from the preceding
PNP buffer by a total of two VBE. This shifts the nominal input
black level such that the LM2432 output (or cathode) black
level voltage is near the nominal cut-off voltage of the CRT.
The overall voltage shift from the processor output to the
LM2432 input is one VBE drop. Note: The same video level
shifting could have been accomplished using one NPN
buffer on the RGB mainboard to drive the processor’s video
output through cabling directly to the LM2432 input. How-
For voltage feedback topologies, it is recommended to use a
high-speed diode to clamp the IK voltage to VBB or a lower
supply during normal video. A small series resistor (RD in
Figure 14) can be placed at the IK pin to limit the current
through the diode when clamping. See the NSC Demonstration Board for an example. For current feedback topologies,
it is recommended to use a high-speed, low-leakage zener
diode to clamp VIK to a properly chosen zener voltage and
shunt the high video current away from the RGB processor’s
IK input. The zener voltage should be higher than the clamping voltage of the processor’s IK pin and lower than the
maximum voltage rating of either the processor’s IK pin or
LM2432 VIK, whichever is less.
In a Direct-View TV application with a single neck PCB, it is
possible for the three LM2432 IK outputs to share the one
feedback circuit and protection diode by connecting the IK
pins together on the neck PCB. This will reduce component
count. In a Rear-Projection TV application with three neck
PCBs, the IK pins can be connected on the central neck PCB
or the RGB processor mainboard through cabling. This way,
they can share the interface circuit to feed back the IK
Application Hints
Application Hints
IK Feedback Circuit
The NSC demonstration neck board was made so that no
modifications to the existing TV circuitry were necessary
(except for replacing the original neck boards). Therefore,
the video interface and IK feedback circuits are designed to
be compatible with those original TV circuits. Referring to
Figure 16, the LM2432 IK output (pin 5) is connected to
protection circuitry before the IK current signal is routed to
pin 4 of connector J8. Diode D1 protects the LM2432 IK pin
from excessive voltage during normal video by clamping to
the VBB supply. Diode D2 isolates the IK output from the
other channels during the active IK measurement interval.
Resistors R17 and R12 limit the current through D1 and D2,
and C12 is used for filtering. From connector J8, the IK
current signal is passed through cabling and combined with
the other two IK signals on the RGB mainboard.
ever, it was decided to preserve the TV’s original RGB
mainboard circuitry (the PNP buffer) and use two NPN transistors on the neck board.
The input stage from the RGB processor to the LM2432 will
be determined by the system designer for his specific application. The input stage required depends mainly on the
following system parameters:
• Nominal CRT cut-off voltage
• Nominal black level output voltage of the RGB processor
• VCC & VBB supply voltages of the LM2432 (determines
DC transfer characteristic)
Once the nominal black level input to the LM2432 establishes a cathode black level near the CRT cut-off voltage, it
can be fine-tuned using the processor’s cut-off adjustment or
calibrated automatically using the IK feedback system, if
applicable. Lastly, some RGB processor video outputs cannot adequately drive the capacitive load introduced by the
cabling between the RGB mainboard and neck boards. To
prevent loading the processor’s output, a NPN or PNP buffer
stage can be applied close to the output on the mainboard to
sufficiently drive the video signal through cabling to the neck
board. It is important to bias the buffer stage(s) properly to
obtain optimal video performance and maintain the full video
adjustment range of the RGB processor.
Video Output and Arc Protection
The routing of the LM2432 output to the CRT is very critical
to achieve optimal video performance and robustness
against arcover. Figure 17 shows the routing and component
placement from VOUT (pin 2) of the LM2432 to the cathode
pin of the CRT socket. The components are placed so that
there is a short, direct path from the LM2432 output to the
cathode. This is done to reduce the PCB parasitic capacitance on the LM2432 output and minimize EMI. Note also
that L3, D3, D4, and R6 are placed to minimize the size of
the video nodes that they are attached to. This enhances the
effectiveness of the arc protection diodes. The anode of
protection diode D3 is connected directly to a section of the
ground plane that has a short, direct path to ground. The
cathode of D4 is connected to VCC very close to decoupling
capacitor C7, which is connected to the same section of the
ground plane as D3. The diode placement and routing is
very important to shunt arcover current away from the output
and minimize the voltage stress on the LM2432. The internal
CRT socket spark gap is essential to significantly reduce the
initial arcover voltage seen at the cathode. The DAG connector should be connected to CRT ground for arc return
Note: The following paragraph describes circuitry that is not
part of the NSC demonstration neck board. The RGB processor, which operates with a voltage feedback IK topology,
uses a single “IK resistor” on the RGB mainboard to convert
all three IK currents into a voltage signal. The IK voltage
signal is then buffered through a PNP transistor before it is
filtered and AC coupled to the RGB processor’s IK input.
This is one implementation of the IK feedback circuit based
on this TV’s specific RGB processor. The system designer
should refer to the RGB processor data sheet to determine
the appropriate feedback circuit implementation for his application.
Supply Decoupling
Note the location of the following components:
• C5 — VCC bypass capacitor with short traces to the VCC
and GND pins of LM2432.
• C7 — VCC bypass capacitor with short traces to the VCC
arc protection diode and ground. This capacitor is very
important for arc protection.
• C9 — VBB bypass capacitor with short traces to the VBB
and GND pins.
C10 and C11 — VCC and VBB electrolytic capacitors
placed near supply pins of LM2432.
Other Items
Connector J1 and switches JP2 & JP4 can be used to
bypass the TV’s internal 200V and 12V supplies and evaluate the LM2432 with external VCC and VBB supplies. Also,
this demonstration board uses medium-sized PCB holes to
accommodate socket pins, which function to allow for multiple insertions of the LM2432 in a convenient manner. To
benefit from the enhanced LM2432 package with thin leads,
the device should be secured with solder in small PCB holes
to optimize the metal-to-metal spacing between the leads.
Application Hints
FIGURE 16. LM2432 Demonstration Board Schematic
Application Hints
FIGURE 17. LM2432 Demonstration Board Layout
(slightly enlarged for more detail)
inches (millimeters)
NS Package Number TE07A
Order Number LM2432TE
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain
no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
National Semiconductor
Americas Customer
Support Center
Email: [email protected]
Tel: 1-800-272-9959
National Semiconductor
Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
National Semiconductor
Asia Pacific Customer
Support Center
Email: [email protected]
National Semiconductor
Japan Customer Support Center
Fax: 81-3-5639-7507
Email: [email protected]
Tel: 81-3-5639-7560
LM2432 220V Monolithic Single Channel 37 MHz HDTV CRT Driver
Physical Dimensions
unless otherwise noted