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LM1237 数据表(PDF) 9 Page - National Semiconductor (TI) |
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LM1237 数据表(HTML) 9 Page - National Semiconductor (TI) |
9 / 42 page Pin Descriptions and Application Information Pin No. Pin Name Schematic Description 1 V Flyback Required for OSD synchronization and is also used for vertical blanking of the video outputs. The actual switching threshold is about 35% of V CC. For logic level inputs C4 can be a jumper, but for flyback inputs, an AC coupled differentiator is recommended, where R V is large enough to prevent the voltage at pin 1 from exceeding V CC or going below GND. C4 should be small enough to flatten the vertical rate ramp at pin 1. C 24 may be needed to reduce noise. 2V REF Bypass Provides filtering for the internal voltage which sets the internal bias current in conjunction with R EXT. A minimum of 0.1 µF is recommended for proper filtering. This capacitor should be placed as close to pin 2 and the pin 4 ground return as possible. 3V REF Current Set External resistor, 10k 1%, sets the internal bias current level for optimum performance of the LM1237. This resistor should be placed as close to pin 3 and the pin 4 ground return as possible. 4 Analog Ground This is the ground for the input analog portions of the LM1237 internal circuitry. 5 6 7 Blue Video In Red Video In Green Video In These video inputs must be AC coupled with a .0047 µF cap. Internal DC restoration is done at these inputs. A series resistor of about 33 Ω and external ESD protection diodes should also be used for protection from ESD damage. 8 10 Digital Ground PLL V CC The ground pin should be connected to the rest of the circuit ground by a short but independent PCB trace to prevent contamination by extraneous signals. The V CC pin should be isolated from the rest of the V CC line by a ferrite bead and bypassed to pin 8 with an electrolytic capacitor and a high frequency ceramic. www.national.com 9 |
类似零件编号 - LM1237 |
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类似说明 - LM1237 |
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