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LM1044N データシート(PDF) 5 Page - National Semiconductor (TI) |
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LM1044N データシート(HTML) 5 Page - National Semiconductor (TI) |
5 / 10 page Pin Description Note The pin designations CV R G B and Sync are as- signed for the convenience of description and are not in- tended to be a limitation For example RGB could be YUV or they could all be independent signal sources Pin 1 Composite video input 1 (CV1) biased internally via 18 kX to VS 2 a 1V Pin 2 Composite video input 2 (CV2) biased as for pin 1 (CV1) above Pin 3 Composite video input 3 (CV3) biased as for pin 1 (CV1) above Pin 4 RGB input R1 This pin is internally biased via a clamp circuit to VS 2 a 1V and should be AC coupled to a low impedance source The input coupling capacitor also acts as a clamp capacitor see application notes Pin 5 RGB input G1 biased as for pin 4 (R1) above Pin 6 RGB input B1 biased as for pin 4 (R1) above Pin 7 Sync input S1 biased internally via 25k to VS 2 a 1V Pin 8 RGB input R2 biased as for pin 4 (R1) above Pin 9 RGB input G2 biased as for pin 4 (R1) above Pin 10 RGB input B2 biased as for pin 4 (R1) above Pin 11 Sync input S2 biased as for pin 7 (S1) above Pin 12 Negative supply (GND) Pin 13 Connect a capacitor to GND to decouple the internal bias of the RGB amplifiers Pin 14 Internal bias for the CV and Sync Amplifiers decouple with a capacitor to GND Pin 15 B Output Pin 16 G Output Pin 17 R Output Pin 18 This is the clamp pulse input pin A positive going pulse activates the RGB input bias clamps See application notes Pin 19 Channel select input control C Pin 20 Channel select input control B Pin 21 Channel select input control A Pin 22 Enable input for control latches Channel selection is locked while this input is low and is updated when high The minimum enable pulse width is 5 ms Pin 23 CV output or Sync output when an RGB channel is selected Pin 24 Supply pin (VS) This pin should be well decoupled at high frequencies a 100 nF capacitor connected close to the supply pins is normally adequate Application Notes DEVICE DESCRIPTION The LM1044 video switch circuit has a configuration as illus- trated in Figure 1 and consists of a 3 input to 1 output 5 MHz switch with 6 dB gain three 2 input to 1 output 30 MHz 0 dB gain switches coupled together with a 2 input to 1 output switch sharing the 3 way switch output All switch stages are current switched differential amplifers with feed- back providing low impedance buffered outputs Latched logic inputs with control decoding are provided for switch control and a DC clamp facility is available on the 30 MHz channels The principle application of this device is the selection be- tween various composite video (CV) or Red Green and Blue (RGB) sources now found in video systems using vari- ous signal sources eg VCR’s satellite receivers home computers and video games Other possible application ex- amples for example security camera switching are shown towards the end of these notes The 5 MHz channels are ideally suited for the switching of composite video sources and have a gain of 6 dB to allow amplification from terminated inputs back up to internal sig- nal levels The 30 MHz channels are suitable for direct RGB inputs to display high quality graphics and will also handle high quality linear signals The fourth switch channel shares the CV output pin and is ideal for routing synchronization signals from the RGBYUV sources into the path to the sync separator and timebase circuits CHANNEL SELECTION The switch selections are made via the enable and 3 logic control inputs according to the truth table shown on the following page This gives a choice of 3 CV video signal sources or 2 RGB plus Sync signals on the video display TLH9252 – 3 FIGURE 1 5 |
同様の部品番号 - LM1044N |
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同様の説明 - LM1044N |
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