General description

lm1283 is a full -featured video amplifier with OSD input, all in a 28 -pin packaging. This part is used for display with a resolution of up to 1280 X 1024. The video part of the LM1283 has three matching video amplifiers. All video amplifiers adjustment functions High input impedance 0V to 4V DC control, providing simple connection to the standard system for bus control. OSD has three TTL inputs and a DC contrast control. The switch between OSD and the video part is controlled by a single TTL input. Although the OSD signal TTL input is internal processing to match OSD logic low level to the video black level. When adjusting the color balance of the driver control the video signal, the color balance of the OSD display will track these colors and color adjustments. LM1283 also has an internal display. Please insert 1208 or 1208 pages into LMD.

Features

Three 140 MHz@ 3 DB Broadband video amplifier (4 VPP output)

TTL OSD input, 50 MHz bandwidth

The film is faint, and the output of the output is below 0.1V

Video/OSD switching speed is 7NS

Independent driving control balance of each channel

0v 4V, high impedance DC contrast control 40 decibel range

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

0V to 4V, high impedance DC flow, high impedance DC OSD comparison control exceeds 40 decibel range

Able to achieve 6.5 VPP output swing (on bandwidth)

Directly drives most mixed or discrete CRT

Application
Application

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Need OSD high -resolution RGB CRT display

Absolute rated value (Note 1)

Power voltage

needle 6, 9, and 22 15V

Peak video output source current (any ampere) needle pin 18, 20 and 23 28 ma

Any input pink voltage (VIN ) VCC≥Vin≥GND Power Consumption (PD)

(25 ° C or TJ based on θja) 2.5W

Environmental thermal resistance (θja) 45 ; C/W

Shell thermal resistance (θjc) 28 ; C/W

Jienon (TJ) 150 ; C

[12]3] Static discharge sensitivity (Note 4) 2 KV

ESD machine model (Note 17) 200V

Storage temperature 65 ; C to+150 ; C

Drawing temperature (welding, 10 seconds) 265 ; C

Working rated value (Note 2)

Temperature range 20 ; C to to to +70 ; C

Power supply voltage (VCC) 11.4V ≤VCC ≤ 12.6V

DC Power

See DC test circuit (Figure 5), TA 25 ℃; vcc1 vcc2 12V; V13 4V; V14 4V; v16 4V; vdrive 4V; v4 0V; v15 0V; v25 1V, unless there is another instructions

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AC electrical characteristics

See AC test circuit (Figure 6), TA 25 ; C, VCC1 VCC2 12V; V4 0V. Manual adjustment video output pins 18, 20, and 23 to the exchange test for 4V DC power, unless there is another instructions (Note 15)

OSD electrical characteristics

See DC test circuit (Figure 5), TA 25 ℃; VCC1 VCC2 12V; V13 4V; V14 4V; v16 4V; vdrive 4V; v4 4V; v15 0V; v25 1V, unless otherwise There are instructions

OSD electrical characteristics (continued)

See DC test circuit (Figure 5), TA 25 ° C; VCC1 VCC2 12V; V13; V13 4V; v14 4V; v16 4V; vdrive 4V; v4 4V; v15 0V; v25 1V, unless there is another instructions

Note 1: Absolutely The maximum rated value indicates the limit 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 pins 6, 9, and 22 must be connected to the outside to prevent internal damage to prevent VCC power -power/power off cycle.

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

Note 5: Typical specifications in+25 ; C below the regulations, represent the most likely parameter specifications.

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

Note 7: The static current of VCC1 and VCC2 with the specified power supply is RL ∞, see the test circuit of Figure 5. The power current of VCC2 (needle 22) also depends on the output load. When the video output is 1V DC, the additional current of the VCC2 is 8 mA for the test circuit of Figure 5.

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

Note 9: Measure the difference between the gain between any two amplifiers. Vehicle recognition number 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 (V13) is 4V or 2V, compared to the maximum conditions of AV, the gain change between any two amplifiers measured by V13 4V. For example, when AV When V13 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 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 speed, a long thread clip may require 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: When v1 v2 v3 0V, and the video input is 0.7V, TR (OSD) 11ns, TF (OSD) 4NS. Video output waveforms will be shown in Figure 3. Therefore, in this case, TR (OSD) is actuallyIt is a decrease time, and TF (OSD) is actually rising.

Note 17: The ESD test of the machine model is included in the standard EIAJ IC-121-1981. A 200 -PF capacitor is charged to the specified voltage, and then discharged directly to an integrated circuit without external series resistance (the resistance of the circuit course must be lower than 50 ).

Typical performance characteristics vcc 12V, TA 25 ; 123]

function description

Figure 1 shows the pins of LM1283 and IC. Each channel receives video signals and OSD signals at its input AM amplifier ( A1). The video/OSD switch signal will also be sent to the input amplifier. The control video is still OSD signal via LM1283. OSD input and video/OSD switch accepts standard TTL signals. After the selection of the mid -frequency video, the TTL low voltage is applied to the pin 4, which is used for OSD A TTL to apply high. When the OSD function is not used, then the pin 4 needs to pass the 47K resistance ground. Although the OSD input signal is a TTL signal, the amplifier processing this signal to match the video level. ATTL high signals will usually be within 100 millivoltage range of video black levels in the white level and TTL low level signals. Please note that by using LM1283, the monitor designer can directly connect the OSD input signal to IC without any signal processing. The right video input execution of DC resumes LM1283. Remember that video input always communicates and couples to the video front. The video input does not have DC standards, so the correct operation of the video input is needed to communicate the coupling monitor. The minimum capacitor is recommended to set 1 μF at the video input pin. The preferred value is 10 μF. Part of the TTL OSD signal processing input the black level of the black level of the OSD signal (TTL) to the black level of the video signal. Tibetan coupling must be used to restore the execution of black electricity matching at the input end. The next stage of LM1283 is a comparison attenuation. Both video and OSD contrast controls enter this stage. In order to facilitate the connection to all control inputs of 5V DAC, including these two controls, the range of 0 to 4 volts. The two contrast controllers did not decay at 4V, and completely attenuated (more than -50 dB) at 0V. Video and OSD contrast adjustment to each other is completely independent, allowing users to set the required contrast display video part without affecting the OSD window. Only one output comes from this section, any adjustment comparison level of the signal path also affects video signals and OSD signals at the same time.

Following the comparison attenuation block is the driver attenuation. PassThe driver attenuation exceeds any adjustment of the video signal to the OSD signal. This configuration simplifies the white level adjustment. When the white level of the video is adjusted, the OSD white level is automatically set. When this uses LM1283, you only need to adjust OSDOSD comparison. Please note that when you execute the white level, you must use the video part of the display, because there are small changes and video levels between OSD levels.

The output level is A2 amplifier. This stage is similar to the LM1205 output level, where the video output can be hidden to the level below the video black level. Black output during the dark disappearance process provides a blank ability on the cathode of the cathode ray tube. In this way, there is no need to use a high -pressure transistor at the G1 of the CRT to perform the anti -faint function. When the output is shielded, LM1283 can also use clamp door. There is a DC recovery in the internal feedback stage. In order to maintain the correct video level based on this feedback circuit, the video output LM1283 must be connected at the impedance end of 390 The required correction voltage required for DC recovery is on the chip. The recommended value is 0.1 μF clamp the lid. If the upper limit value is too small, it will occur (offset) the DC level of the video output during horizontal scanning. If the upper limit value is too large, the DC recovery circuit may not be able to keep the video signal. Because the recovery of DC power is also input on the video, the larger the tip head value, the smaller the problem is that compared with most other video front placing vessels, LM1283. The reference level of the DC recovery circuit is set at RGB cutting adjustment (sales 25). Most monitor applications AC couples the front placedrior output to the cathode drive. Therefore, only one cut -off adjustment is provided, which is the operation that mainly optimizes the cathode drive. Please note that the blank and tong -shaped gates are in a low activation state. These pins are usually controlled by standard TTL signals. For video applications, a clamping grid must be used. There is a design that does not require blank functions. It is not necessary to pour the mouth, and you must use pulling it to tie it to a high resistor. The resistance value is 47K is acceptable 4V or 12V. -A2's gain is controlled by the driver. These are the control voltage of 0V to 4V. 4V causes A2 and 0V to cause 12 db attenuation. 12 DB AD adjustment range should provide sufficient adjustment to set the white level. Note that the range of 12 decibels is given a 4 to 1 range channel between the three output levels.

The application of LM1283

The schematic diagram of the demonstration board is shown in Figure 7. The board is described by the characteristic of LM1283. Please note that 33 all inputs of the resistor and IC to receive external signals. These resistors are necessary protective integrated circuits from the impact of sudden voltage impact In power supply and power -off mode, or connect the display to other devices. The monitor designer must include these resistors in the design. If it is additional, it is necessary to perform anti -static protection at the video input terminal, and then at 33 The IC side of the resistor to add clamping diodes is desirable-

The application of LM1283 (continued)

Suggestion: one connection VCC1, one ground. Under normal circumstances, designers may want to insert an additional ESD protection input for video for video. Remember that the input capacitor to the video input is also part of the DC recovery circuit. The maximum circuit resistance of this circuit is about 110 . The value of the resistor should not increase. Designers can choose to reduce the 10μF video input capacitor to 1 μF. Internal ESD protection and external clamping diodes, one connected+12V, and the other will provide excellent electrostatic protection. The interface to OSD input is quite easy, because the signal that the processing level required to match the OSD signal and video matching is completed by the LM1283. However, the appropriate design skills must be followed to ensure that the TTL signal is received in LM1283. The ground bouncing TTL signal may cause the switching time to have multiple switching functions. This effect can lead to the quality of degenerate display of OSD window. The last TTL stage needs to be located near LM1283 to ensure cleaning the TTL signal. The transmission delay is another that can reduce the quality of OSD display. The best condition is that all OSD signals come from a register, maintaining changes in the transmission delay below 5NS. If the OSD function is not used, or the line may have been disconnected from some test operations, then the video/OSD switching pin (pin 4) must have a drop -down resistance place to ensure the operation in the video mode. The use of a 47K drop -down resistor will lower this needle and provide sufficient resistance to where the pins can still be driven directly by the TTL signal. Needle 1 to 3 should also be terminated in the same way, eliminating the possibility of the possibility of switching logic levels from noise. Figure 2 to 4 shows LM1283. When the measuring transmission delay, all TTL signals are set to 4 VPP when the output is measured when crossing 1.3V. When the output is half (change to 2V). The decrease of the rising video output is 10%and 90%of the transition point.

In high -frequency applications, the circuit board layout is always crucial, for example, LM1283. Improper layout can cause the video waveform after the sudden conversion, or partially may oscillate. A good ground plane and suitable+12V wiring are important steps for good PCB layout. LM1283 can be good -looking. It is recommended to use ground planes, it is best to isolate the output level grounding from the rest of the circuit. In addition, the two grounds should only be at one point. Ideally, the ground cable is connected to the circuit board to ground. Yes, all ground wires are connected inside, but the trace wire resistance can still allow the ground to rebound enough vibration feedback. Output -level power supply needle pin 22 and other power pins. This pin must be connected to the+12V power supply, and it is best to use high -frequency isolation. This is a pins between the iron oxygen magnet beads that are easy to achieve 22And+12V power supply.Figure 8 and 9 show the waveforms obtained by using a single -sided demonstration board LM1283 for this part.