LM2409 [NSC]

Monolithic Triple 9.5 ns CRT Driver; 单片三重9.5纳秒的CRT驱动器


型号：	LM2409
厂家：	National Semiconductor
描述：	Monolithic Triple 9.5 ns CRT Driver 单片三重9.5纳秒的CRT驱动器驱动器
文件：	总9页 (文件大小：1063K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

August 1999

LM2409

Monolithic Triple 9.5 ns CRT Driver

n Well matched with LM1279 video preamp

n 0V to 5V input range

n Stable with 0 pF–20 pF capacitive loads and inductive

peaking networks

n Convenient TO-220 staggered lead package style

n Standard LM240X Family Pinout which is designed for

easy PCB layout

General Description

The LM2409 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 chan-

nel has its gain internally set to −14 and can drive CRT ca-

pacitive loads as well as resistive loads present in other ap-

plications, limited only by the package’s power dissipation.

Applications

n 1024 x 768 Displays up to 70 Hz Refresh

n Pixel clock frequencies up to 75 MHz

n Monitors using video blanking

The IC is packaged in an industry standard 11-lead TO-220

molded plastic power package. See Thermal Considerations

section.

Features

n Dissipates approximately 50% less power than the

LM2406

Schematic and Connection Diagrams

DS100838-2

Note: Tab is at GND

Top View

Order Number LM2409T

DS100838-1

FIGURE 1. Simplified Schematic Diagram

(One Channel)

DS100838

www.national.com

Absolute Maximum Ratings (Notes 1, 3)

Machine Model

250V

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Operating Range (Note 2)

V_CC

+60V to +85V

+8V to +15V

Supply Voltage, (V_CC

Bias Voltage, (V_BB

Input Voltage, (V_IN

)

+90V

+16V

V_BB

)

V_IN

+0V to +5V

)

0V to 6V

V_OUT

+15V to +75V

−20˚C to +115˚C

Storage Temperature Range, (T_STG

Lead Temperature

)

−65˚C to +150˚C

Case Temperature

Do not operate the part without a heat sink.

(Soldering, 10 sec.)

300˚C

2 kV

ESD Tolerance, Human Body Model

Electrical Characteristics

(See Figure 2 for Test Circuit)

Unless otherwise noted: V_CC= +80V, V_BB= +12V, V_IN= +2.7 V_DC, C_L= 8 pF, Output = 40 V_PPat 1 MHz, T_C= 50˚C.

LM2409

Symbol

Parameter

Supply Current

Condition

Units

Min

Typ

Max

I_CC

Per Channel, No Input Signal, No

Output Load

I_BB

V_OUT

A_V

Bias Current

DC Output Voltage

DC Voltage Gain

Gain Matching

Linearity Error

Rise Time

All Three Channels

−14

1.0

No AC Input Signal, V_IN= 1.2V

No AC Input Signal

V_DC

−12

−16

∆A_V

(Note 4), No AC Input Signal

(Notes 4, 5), No AC Input Signal

(Note 6), 10% to 90%

(Note 6), 90% to 10%

(Note 6)

t_R

t_F

Fall Time

Overshoot

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 = 1.0V to V = 4.5V.

IN IN

Note 6: Input from signal generator: t , t

1 ns.

AC Test Circuit

DS100838-3

Note: 8 pF load includes parasitic capacitance.

FIGURE 2. Test Circuit (One Channel)

Figure 2 shows a typical test circuit for evaluation of the LM2409. This circuit is designed to allow testing of the LM2409 in a 50Ω

environment without the use of an expensive FET probe. The 4950Ω resistor at the output forms a 100:1 voltage divider when

connected to a 50Ω load.

www.national.com

Typical Performance Characteristics (V_CC80V, V_BB12V, C_L8pF, V_OUT40V_PP(25V-65V),

Test Circuit - Figure 2 unless otherwise specified)

DS100838-4

DS100838-7

FIGURE 3. V_OUTvs V_IN

FIGURE 6. Power Dissipation vs Frequency

DS100838-5

DS100838-8

FIGURE 4. Speed vs Temperature

FIGURE 7. Speed vs Offset

DS100838-6

FIGURE 5. LM2409 Pulse Response

DS100838-9

FIGURE 8. Speed vs Load Capacitance

www.national.com

over are designed specifically for the LM2409. If another

member of the LM240X family is used, please refer to its

datasheet.

Theory of Operation

The LM2409 is a high voltage monolithic three channel CRT

driver suitable for high resolution display applications. The

LM2409 operates with 80V and 12V power supplies. The

part is housed in the industry standard 11-lead TO-220

molded plastic power package.

POWER SUPPLY BYPASS

Since the LM2409 is a wide bandwidth amplifier, proper

power supply bypassing is critical for optimum performance.

Improper power supply bypassing can result in large over-

shoot, ringing or oscillation. A 0.01 µF capacitor should be

connected from the supply pin, V_CC, to ground, as close to

the supply and ground pins as is practical. Additionally, a

10 µF to 100 µF electrolytic capacitor should be connected

from the supply pin to ground. The electrolytic capacitor

should also be placed reasonably close to the LM2409’s

supply and ground pins. A 0.1 µF capacitor should be con-

nected from the bias pin, V_BB, to ground, as close as is prac-

tical to the part.

The circuit diagram of the LM2409 is shown in Figure 1. 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 −14. Emitter followers Q3 and Q4 iso-

late 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 bi-

asing to the output emitter follower stage to reduce cross-

over distortion at low signal levels.

Figure 2 shows a typical test circuit for evaluation of the

LM2409. This circuit is designed to allow testing of the

LM2409 in a 50Ω environment without the use of an expen-

sive FET probe. In this test circuit, two low inductance resis-

tors in series totaling 4.95 kΩ form a 100:1 wideband, low

capacitance probe when connected to a 50Ω coaxial cable

and a 50Ω load (such as a 50Ω oscilloscope input). The in-

put signal from the generator is ac coupled to the base of

Q5.

ARC PROTECTION

During normal CRT operation, internal arcing may occasion-

ally occur. Spark gaps, in the range of 200V, connected from

the CRT cathodes to CRT ground will limit the maximum volt-

age, but to a value that is much higher than allowable on the

LM2409. This fast, high voltage, high energy pulse can dam-

age the LM2409 output stage. The application circuit shown

in Figure 9 is designed to help clamp the voltage at the out-

put of the LM2409 to a safe level. The clamp diodes, D1 and

D2, should have a fast transient response, high peak current

rating, low series impedance and low shunt capacitance.

FDH400 or equivalent diodes are recommended. Do not use

1N4148 or equivalent diodes for the clamp diodes. D1 and

D2 should have short, low impedance connections to V_CC

and ground respectively. The cathode of D1 should be lo-

cated very close to a separately decoupled bypass capacitor

(C3 in Figure 9). The ground connection of D2 and the de-

coupling capacitor should be very close to the LM2409

ground. This will significantly reduce the high frequency volt-

age transients that the LM2409 would be subjected to during

an arcover condition. Resistor R2 limits the arcover current

that is seen by the diodes while R1 limits the current into the

LM2409 as well as the voltage stress at the outputs of the

device. R2 should be a 1/2W solid carbon type resistor. R1

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 lev-

els that the LM2409 would be subjected to. The inductor will

not only help protect the device but it will also help maximize

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 9.

Application Hints

INTRODUCTION

National Semiconductor (NSC) is committed to provide ap-

plication information that assists our customers in obtaining

the best performance possible from our products. The follow-

ing information is provided in order to support this commit-

ment. 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 com-

ponent 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 pur-

poses. When working with high bandwidth circuits, good lay-

out practices are also critical to achieving maximum perfor-

mance.

IMPORTANT INFORMATION

The LM2409 performance is targeted for the VGA (640 x

480) to XGA (1024 x 768, 70 Hz refresh) resolution market.

It is designed to be a replacement for discrete CRT drivers.

The application circuits shown in this document to optimize

performance and to protect against damage from CRT arc-

DS100838-10

FIGURE 9. One Channel of the LM2409 with the Recommended Arc Protection Circuit

www.national.com

This example assumes a capacitive load of 8 pF and no re-

sistive load.

Application Hints (Continued)

OPTIMIZING TRANSIENT RESPONSE

TYPICAL APPLICATION

Referring to Figure 9, there are three components (R1, R2

and L1) that can be adjusted to optimize the transient re-

sponse of the application circuit. Increasing the values of R1

and R2 will slow the circuit down while decreasing over-

shoot. Increasing the value of L1 will speed up the circuit as

well as increase overshoot. It is very important to use induc-

tors with very high self-resonant frequencies, preferably

above 300 MHz. Ferrite core inductors from J.W. Miller Mag-

netics (part # 78FR82K) were used for optimizing the perfor-

mance of the device in the NSC application board. The val-

ues shown in Figure 9 can be used as a good starting point

for the evaluation of the LM2409. The NSC demo board also

has a position open to add a resistor in parallel with L1. This

resistor can be used to help control overshoot. Using vari-

able resistors for R1 and the parallel resistor will simplify

finding the values needed for optimum performance in a

given application. Once the optimum values are determined

the variable resistors can be replaced with fixed values.

A typical application of the LM2409 is shown in Figure 10.

Used in conjunction with an LM1279, a complete video chan-

nel from monitor input to CRT cathode can be achieved. Per-

formance is ideal for 1024 x 768 resolution displays with

pixel clock frequencies up to 75 MHz. Figure 10 is the sche-

matic for the NSC demonstration board that can be used to

evaluate the LM1279/2409 combination in a monitor.

PC BOARD LAYOUT CONSIDERATIONS

For optimum performance, an adequate ground plane, isola-

tion between channels, good supply bypassing and minimiz-

ing unwanted feedback are necessary. Also, the length of the

signal traces from the preamplifier to the LM2409 and from

the LM2409 to the CRT cathode should be as short as pos-

sible. The following references are recommended:

Ott, Henry W., “Noise Reduction Techniques in Electronic

Systems”, John Wiley & Sons, New York, 1976.

“Guide to CRT Video Design”, National Semiconductor Appli-

cation Note 861.

EFFECT OF LOAD CAPACITANCE

Figure 8 shows the effect of increased load capacitance on

the speed of the device. This demonstrates the importance

of knowing the load capacitance in the application.

“Video Amplifier Design for Computer Monitors”, National

Semiconductor Application Note 1013.

Pease, Robert A., “Troubleshooting Analog Circuits”,

Butterworth-Heinemann, 1991.

EFFECT OF OFFSET

Because of its high small signal bandwidth, the part may os-

cillate in a monitor if feedback occurs around the video chan-

nel through the chassis wiring. To prevent this, leads to the

video amplifier input circuit should be shielded, and input cir-

cuit wiring should be spaced as far as possible from output

circuit wiring.

Figure 7 shows the variation in rise and fall times when the

output offset of the device is varied from 40 V_DCto 50 V_DC

The rise time shows a maximum variation relative to the cen-

ter data point (45 V_DC) of about 21%. The fall time shows a

variation of about 3% relative to the center data point.

THERMAL CONSIDERATIONS

NSC DEMONSTRATION BOARD

Figure 4 shows the performance of the LM2409 in the test

circuit shown in Figure 2 as a function of case temperature.

The figure shows that the rise time of the LM2409 increases

by approximately 3% as the case temperature increases

from 50˚C to 100˚C. This corresponds to a speed degrada-

tion of 0.6% for every 10˚C rise in case temperature. The fall

time increases by approximately 3% which corresponds to a

speed degradation of 0.6% for every 10˚C rise in case tem-

perature.

Figure 11 shows routing and component placement on the

NSC LM1279/2409 demonstration board. The schematic of

the board is shown in Figure 10. This board provides a good

example of a layout that can be used as a guide for future

layouts. Note the location of the following components:

•

C55 — V_CCbypass capacitor, located very close to pin 6

and ground pins

C43, C44 — V_BBbypass capacitors, located close to pin

10 and ground

Figure

6 shows the maximum power dissipation of the

LM2409 vs Frequency when all three channels of the device

are driving an 8 pF load with a 40 V_p-palternating one pixel

on, one pixel off signal. The graph assumes a 72% active

time (device operating at the specified frequency) which is

typical in a monitor application. The other 28% of the time

the device is assumed to be sitting at the black level (65V in

this case). This graph gives the designer the information

needed to determine the heat sink requirement for the appli-

cation. The designer should note that if the load capacitance

is increased the AC component of the total power dissipation

will also increase.

C53–C55 — V_CCbypass capacitors, near LM2409 and

V_CCclamp diodes. Very important for arc protection.

The routing of the LM2409 outputs to the CRT is very critical

to achieving optimum performance. Figure 12 shows the

routing and component placement from pin 1 of the LM2409

to the blue cathode. Note that the components are placed so

that they almost line up from the output pin of the LM2409 to

the blue cathode pin of the CRT connector. This is done to

minimize the length of the video path between these two

components. Note also that D14, D15, R29 and D13 are

placed to minimize the size of the video nodes that they are

attached to. This minimizes parasitic capacitance in the

video path and also enhances the effectiveness of the pro-

tection diodes. The anode of protection diode D14 is con-

nected directly to a section of the the ground plane that has

a short and direct path to the LM2409 ground pins. The cath-

ode of D15 is connected to V_CCvery close to decoupling ca-

pacitor C55 (see Figure 12) which is connected to the same

section of the ground plane as D14. The diode placement

and routing is very important for minimizing the voltage

The LM2409 case temperature must be maintained below

115˚C.

If the maximum expected ambient temperature is 70˚C and

the maximum power dissipation is 3.4W (from Figure 6, 40

MHz bandwidth) then a maximum heat sink thermal resis-

tance can be calculated:

www.national.com

Application Hints (Continued)

stress on the LM2409 during an arc over event. Lastly, notice

that S3 is placed very close to the blue cathode and is tied

directly to CRT ground.

www.national.com

Application Hints (Continued)

DS100838-14

FIGURE 11. LM1279/240X Demo Board Layout

www.national.com

Application Hints (Continued)

DS100838-15

FIGURE 12. Trace Routing and Component Placement for Blue Channel Output

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted

NS Package Number TA11B

Order Number LM2409T

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR 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

Corporation

Americas

Tel: 1-800-272-9959

Fax: 1-800-737-7018

Email: support@nsc.com

National Semiconductor

Europe

National Semiconductor

Asia Pacific Customer

Response Group

Tel: 65-2544466

Fax: 65-2504466

National Semiconductor

Japan Ltd.

Tel: 81-3-5639-7560

Fax: 81-3-5639-7507

Fax: +49 (0) 1 80-530 85 86

Email: europe.support@nsc.com

Deutsch Tel: +49 (0) 1 80-530 85 85

English Tel: +49 (0) 1 80-532 78 32

Français Tel: +49 (0) 1 80-532 93 58

Italiano Tel: +49 (0) 1 80-534 16 80

Email: sea.support@nsc.com

www.national.com

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.

LM2409 [NSC]

相关型号：

LM2409T

LM240K12

LM240K15

LM240K5

LM240WU8

LM240WU8-SLA2

LM240Z

LM241

LM2412

LM2412A

LM2412ATA

LM2412ATA