General description

LM1279A is a full -featured and low -cost video amplifier with OSD (screen display). 8V low -power operation improves reliability. Use 20 -pin DIP packaging, which can accommodate very compact video channel design requires OSD. All video functions are input from 0V to 4V. This can easily connect to the application calibration system of a 5V digital converter in the computer control system. The unique OSD switch does not require the OSD switch signal. An OSD signal at any OSD input terminal is switched to OSD mode within 5 nan seconds. The ideal low -cost OSD display video amplifier maximum 1024 x 768. LM1279A provides excellent protective anti -static electricity. In the new MC13282 alternative design.

Features

Three 110 MHz@ 3DB Broadband video amplifier (4VPP output)

OSD signal to any OSD input pins automatic switch

All 3 outputs to OSD mode

Quick OSD switching time, usually 5 nano seconds

3.5 kv ESD protection

Fixed deadline level is usually set to 1.2 V

0V to 4V, high impedance DC contrast control

40 decibel range

0V to 4V, high impedance DC driver control (0 db to 12 db Scope)

N match (± 0.1 db or 1.2%) attenuator used for contrast

Control

Directly drives most mixed or discrete CRT [ 123]

Application

High -resolution RGB CRT display

Video AGC amplifier

Broadband amplifier with contrast and drive control

] N interface amplifier used for LCD or CCD system

Absolute maximum rated value (Note 1)

Power voltage

] Needle 2 and 16 (Note 3) 10V

Peak video output source current

(any ampere) needle 13, 15 or 18 28 ma

Any input pin pin Voltage (VIN) vcc ≥Vin≥GND

Power Consumption (PD)

(25 ° C or TJ based on θja) 2.1W

Environmental thermal resistance ( θJa) 60 ; c/w

The shell thermal resistance (θja) 37 ; C/W

[TJ) 150 ; C

ESD ESD Sensitivity (Note 4) 3.5 kV

ESD machine model (Note 16) 300V

Storage temperature 65 ; C to 150 ; C

] Diversion temperature (welding, 10 seconds) 265 ; c

Working rated value (Note 2)

The temperature range 0 ; c to 70 ; 123] Power voltage (VCC) 7.5V ≤VCC ≤ 8.5V

DC Phase Feature

TA u003d 25 ; C; VCC1 u003d VCC2 u003d 8V; V10 u003d 4V; V driver u003d 4VV ; V11 u003d 7V; VOSD u003d 0V, unless there is another instructions

AC electrical characteristics

ta u003d 25 ; c; vcc1 u003d vcc2 u003d 8V Essence Unless there are other regulations, manually adjust the video output pins 13, 15 and 18 to 4V DC for communication and test regulations. (Note 15)

AC electrical characteristics (continued)

TA u003d 25 ; c; vcc1 u003d vcc2 u003d 8V. Unless there are other regulations, manually adjust the video output pins 13, 15 and 18 to 4V DC for communication and test regulations. (Note 15)

Note 1: Absolute maximum rated value indicates the limit value that may cause damage.

Note 2: The working rated value indicates the conditions of the equipment, but does not guarantee specific performance restrictions. For the guarantee specifications and test conditions, see the electrical characteristics. The guarantee specifications are only applicable to the test conditions listed. When the device does not run under the test conditions, certain performance characteristics may be downgraded.

Note 3: VCC power plugging 2 and 16 must be connected together to prevent internal damage from the VCC power -power/power -off cycle.

Note 4: Human model, 100 PF discharge through 1.5 k resistor.

Note 5: The typical specifications are specified under+25 ; C, which represents the most likely parameter specifications.

Note 6: The detection limit is guaranteed to be national AOQL (the average factory quality level).

Note 7: The current specified power supply is reduced by the current of VCC1 and VCC2.IsupPly u003d ICC1+ICC2 IL). VC16 pin power supply depends on the output load. When the video output is 1V DC, the additional current of VCC2 is 7.7 ma, RL u003d 390

Note 8: The output voltage depends on the load resistance. The test circuit uses RL u003d 390 .

Note 9: Measure the difference between the gain between any two amplifiers. Vehicle recognition number u003d 635 MVPP.

Note 10: #8710; AV Track is the measurement of the ability to track any two amplifiers, and quantifies the matching of three attenuers. The difference is that when the comparison voltage (V10) is 4V or 2V, compared to the maximum conditions of AV, the gain change between any two amplifiers measured by V10 u003d 4V. For example, when AV When V10 u003d 2V, the maximum gain of the three amplifiers is 17.1DB, 16.9DB, and 16.8DB, respectively, and become 11.2DB, 10.9DB, and 10.7DB, respectively, so Essence

Note 11: When measuring the bandwidth or pulse of the video amplifier, it is recommended to use the double -sided full -ground plane printing circuit board with a non -socket without sockets. The quarantine test of the 10 MMS of the video amplifier also requires this printing circuit board. The reason for the two -sided full -ground plane PCB is that the measured value is too large, a single -sided polychloropenezen will change.

Note 12: Adjust the input frequency from 10 MHz (the maximum reference level of AV) to 3 DB to angle frequency (f 3 dB).

Note 13: Measure the output level of the other two unavailable amplifiers relative to the driver amplifier to determine the channel interval. Termid the input of the unavailable amplifier simulation generator load. For VSEP 10 MHz, repeat the test under FIN u003d 10 MHz.

Note 14: For the horizontal line of 15kHz, the minimum pulse width is 200NS. This limit is guaranteed by design. If you use a lower line rate, a longer one may require clamping pulse.

Note 15: During the exchange test, the 4V DC level is the central voltage of the exchange output signal. For example, if the output is 4 VPP, the signal will swing between 2V DC and 6V DC power.

Note 16: The ESD test of the machine model is included in the standard EIAJ IC-121-1981. A 200 -PF capacitor charges to the specified voltage, and then discharged directly to an integrated circuit with no external series resistance (the resistance of the discharge channel must be less than 50 ).

Note: All video input must have one 30 series resistors to prevent EOS (electricity stress). If the OSD signal is outside the monitor, or when the+8V is not fully powered, these signals will appear at any time, then OSD input also requires a 30 series resistor.

ESD and arc are protected

The ESD battery of the LM1279A is improved than the ESD battery. When designing LM1279A, the monitor design must use a good PC plate layout technology. The sensitivity of these components of human model ESD is set to 3 kV (Note 4). However, many monitor manufacturers are now testing monitors that comply with IEC 801-2 specifications. This requires the input of the monitor to withstand 8 kv discharge. If the display designer hopes to survive at this level, it must provide an external ESD protection input for the video prefabrication! In the LM1279A AS, the PC plate layout is very important to place a large prefabrication with other videos. The LM1279A provides excellent electrostatic discharge and arc discharge, but LM1279A is not a substitute for a good PCB layout. Figure 5 shows a video presence of a video. The two diodes of the input end of the video provide the best protection anti -static after the series of diode input end of the large input terminal at 30 #8486. When this protection and good PCB layout, the video prefabricated vessel will easily pass the IEC801-2 4 (8 KV ESD) test. The monitor is usually completed by the monitor. If the protective diode is moved to the video input terminal, there is 30 resistance, and then ESD protection will reduce efficiency. It may also damage the diode because there is no resistance to restriction current. The design of a more load diode, such as FDH400, should be used. It is strongly recommended to add a protection code, as shown in Figure 5. 1N4148 diode has the maximum capacitor of 4 PF. This will not have any impact due to the low impedance of the input video, the video system response.

Instead of the two diodes of the recommended video front place input end. The position required by the Qina diode is in FIG. 5. It is displayed as the dotted line, indicating the inherent changes of the dual diode solution. The Qina diode does save a component, but now the protection is less effective. In order to minimize the capacitance, the Qina diode requires the Qina voltage to be 24V or higher. This far exceeds the VCC voltage of LM1279A. The Qina diode must be located at the video input end to prevent low voltage surge. It needs 30 resistors to limit this current voltage waves to protect the video presence of the video. The effect of protecting the use of Zina diode to prevent static discharge and two diode (and Zina diode) at the video input end. It may require a higher series resistance to protect the Qina voltage, but the higher resistance value will damage the performance of LM1279A; the result is that the bandwidth is low and the black level is unstable. The maximum that the monitor designer should not considerLM1279A, ESD protected by the Qina diode solution. The ESD battery of LM1279A also has good tolerance anti -arc. Once again, the monitor designer must be careful on his printing circuit board and protect it with good arcs. Only the output of the CRT driver is directly exposed to the overvoltage of the arc. A good PCB layout is the best protection anti -arc of video front placed. The vulnerabilities of the front amplifier are mainly through the ground traces on the PCB. In order to correctly operate the ground connection related to the video front placing large, including the grounding of the bypass container, there must be a short circuit of grounding. Important horizon is used to connect all front plattoral ground ground ground. Figure 16, the layout of the demonstration board is a good example, on an effective ground plane, but only the single -sided PCB layout is used. This is a checklist to ensure that the PC board layout is good:

All ground planes related to the video front plattifier are connected together through a large ground plane.

The CRT driver is connected to the video front placement to ground.

CRT and arc protective grounding directly connected to the chassis or main land. There is no arc over current flowing from these grounding through the front placed large or cathode ray tube driver ground. If you do not follow any of the above suggestions, LM1279A may be easily affected by the arc. So far, grounding is the most common cause of the faulty of the videos of the videos during the arc period.

function description

Homepage shows the pins of LM1279A and IC. Each channel receives a video input signal at its input amplifier (-a1). The output of this input amplifier to the contrast attenuator stage. In order to facilitate the connection to all control inputs of 5V DAC, including contrast control, the range of 0V to 4V is used. The transmission control was not attenuated under 4V input, and attenuation (exceeding 40 dB), and the input voltage was 0V. All three channels will set the comparison control at the accurate tracking pin to set the attenuation of 10 per channel at the same time for the given input voltage, usually within the range of ± 0.3 dB. Because the contrast control is the first step, all channels are tracked at attenuation and internal control voltage generated input voltage to all three channels are public. The output of the contrast attenuator to the driver At Tenuator. At this stage, there is a control range of 12 decibels. This stage is used for color balance, so the adjustment range is limited to 12 decibels to obtain more accurate color balance.

Function description (continued)

The channel has its own independent control pipe foot, 0V to 4V control range. When a 4V input does not attenuate input 0V, attenuation is attenuation 12 decibels. The output of the driver attenuation enters the inverter input A2. Since this is the second reversal stage, the loser of A2It will be a non -reversal video signal. Note the output of GM1 to the non -inverter input of A2. Please note that the output of A2 is output to the inverter input of GM1. This is the feedback of the clamp circuit. The output level of A2 is accurate replication through the video output from A3. If 390 load impedance is used for video output, and then output -level black levels will accurately track output A2. Another input of GM1 is the expected black level output because the LM1279A has a fixed black level output, and the non -reversing input of the GM1 in all three channels is transferred to a fixed 1.35V internal reference. This is the black level output to the nominal 1.35V. The role of GM1 is similar to samples and maintenance amplifiers. Once the pulse of the clamp exceeding 3.6V GM1 is activated, the input of the A2 input to the video output voltage is 1.35V. In order to correctly restore DC power, this is very important that GM1 is activated at the horizontal scanning time when the video is at a black level. GM1 also clamped the lamp cover to the correct voltage to maintain a black video output level of 1.35V. When the GM1 is closed, the voltage can be kept on the cap to maintain the correct black level during the video video, thereby restoring 1.35V black levels. The input of A3 receives the output from A2. A3's video channel is replication from output level to A2. As described in the previous paragraph, this is to be completed in the A2 stage. A3 also received OSD input to clear the channel without OSD input. By performing DC recovery in the A2 stage, OSD can be completed in A2 during the output phase of the DC recovery period.

OSD signal enters a special interface circuit. The output of this circuit will drive A3 to OSD black level or about 2.4V higher than the video black level (OSD white level). OSD's black and electricity is about 300 millivolttility, which is lower than the black level of video. This guarantees that if the OSD signal is not activated for specific channels, but its output will be slightly lower than the critical level. If an OSD input is received to a specific channel, the video output will be at OSD white level. If any video has only one OSD signal, the OSD mode will automatically activate the channel. The OSD control circuit will allow any colors other than black in OSD mode. This also saves a special signal switch to OSD mode. Remember that at least one OSD input must be high to enable the OSD mode, so black cannot be used in the OSD window.

The application of LM1279A

The two demonstration boards can be used to evaluate LM1279A. A board is a prefabricated large -scale demonstration board. The board is used to test and characterize LM1279A. The schematic diagram of this board is shown in Figure 4 The printing circuit layout of the circuit board is shown in the Figure 6. Another plate is a complete video channel neck panel that can be directly inserted into the CRT socket. The circuit diagram of the circuit board is shown in Figure 9, and the layout of the printing circuit board is shown in Figure 10. The CRT driver is used for this board is LM2407. Any countryThe single -sheet cathode driver of the home can be used for this board, but based on cost and performance, LM2407 is considered the best match for LM1279A. Some of the important notes in Figure 4. All three video inputs are 75 video system is equipped with 75 ending resistors. This is a normal video impedance system for computer video. There may also be 50 system, and then R1, R3 and R5 will be changed to 50 R2, R4, and R6 are connected in series with the video input with LM1279A. These three require 30 resistors to protect ICs from being influenced by any emergencies in power and power shutdown mode, or connect the display to other modes. The display designer must include these resistors in its design to obtain good monitor reliability. If you need to perform additional anti -static protection on the video input terminal, add a clamp diode to the IC side of the resistor at 30 one connect VCC1 and one ground (see Figure 5) 1. Sometimes designers may want to add 30 resistance at the video input terminal for additional ESD protection. It is not recommended to use LM1279A. C5, C7, and C9 are part of the DC recovery circuit. This circuit depends on the total maximum circuit resistance of about 110 ; 30 input series resistors and video terminal national resistors 75 Increase the value of 30 the resistor will exceed 110 limit. The excellent internal ESD protects the external clamping diodes (if required), it will provide excellent ESD protection. The 30 the resistor is also required if the OSD signal is outside the monitor, or if the signal does not exist when the+8V does not exist. The interface to OSD input is quite easy to complete the signal processing required to match the OSD signal and video electricity level. LM1279A is completed internally. No OSD window signal is required. At any time, any of the three OSD inputs have a high TTL signal LM1279A that will automatically switch to OSD mode. The climax TTL OSD signal will provide high video output for the color. The OSD level is fixed, usually 2.3V level higher than video black. This will provide a fixed brightness for the OSD window, but it is not the biggest video brightness, which may be unpleasant users. Figure 2 and 3 show the OSD signal chart of the time arrangement LM1279A. The proposed load impedance of LM1279A is 390 . However, some changes in load impedance. If the load impedance is reduced, the monitor designer must confirm that the part is still in the normal working mold temperature range, and must not exceed the mold temperature. When the load impedance is changed, the black horizontal displacement is shown in the figure below. The measured VP-P also lists outputs with less than 1%.

Load VP-P BLK. Horizontal displacement

430 3.62V+15 millival

390 3.62V 0 millival

330 3.58V 25 millival

270 #8486; 3.51v 45 millivolttility

When using lower load impedance, LM1279A can indeed be tailored more quickly. This does reduce the space for video output. In high -frequency applications, the circuit board layout is always crucial, for example, using LM1279A. If the layout is not good, it may cause the video waveform to occur after the sudden conversion, or part may oscillate. A good ground plane and suitable+8V wiring are an important step of a good PCB layout. LM1279A does need to be on VCC1 and VCC2 (needle 2 and 16). Figure 6 and 10 clearly show this point. There are short and large trace thread needle 2 and 16 in the figure. Both demonstration boards provide a good example of a monitor with LM1279A. These boards are single -sided allowed LM1279A to run with its highest performance. This neck plate also shows a good example of the CRT driver and CRT. The video signal path is kept as short as possible between LM1279A and CRT drivers, and between the CRT driver and the CRT socket. The performance of the actual LM1279A placed in the video front of the video is shown in Figure 7 and Figure 8.