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TDA4504B Fiches technique(PDF) 8 Page - NXP Semiconductors |
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TDA4504B Fiches technique(HTML) 8 Page - NXP Semiconductors |
8 / 26 page February 1992 8 Philips Semiconductors Product specification Small signal combination for multistandard colour TV TDA4504B 50/60 Hz Information In the external video mode and with a resistor of 1 M Ω from pin 25 to VCC the mute is overruled by the 50/60 Hz information from the divider system. 50/60 Hz Truth Table: VCR switch Flywheel horizontal synchronization is desirable when receiving weak signals marred by noise but is usually unnecessary when receiving stronger off-air signals unless certain types of interference or multipath reception are apparent. Due to the inherent instability of VCR signals, however, the horizontal time constant should be shorter to prevent loss of horizontal synchronization in the early part of the scan. Provision is therefore incorporated to automatically switch the short time constant such that a strong signal instigates the 'VCR' mode and a weak signal triggers the 'TV' mode. The connection of a switch to pin 17 provides for this to be accomplished manually and may take the form of an auxiliary switching function associated with a designated program selector button. The TDA4504B has a separate pin (pin 17) for the VCR switch: Video-switch Video output from the demodulator is filtered to remove the audio carrier and DC-coupled to pin 16. If AC-coupling is employed the internal noise clamp will operate on sync. tips. The TDA4504B provides the opportunity for a direct video connection (e.g. via a peritel connector) to be made to the device at pin 13. Selection between internal and external video is made by applying a switching potential to pin 18. Video switch: Gain reduction To prevent crosstalk between the IF stages and the horizontal oscillator when the device is operated in its external video mode with no RF input, the TDA4504B incorporates an option to reduce IF gain by 20 dB. This is accomplished by connecting a 39 k Ω resistor between pin 17 and ground. Omission of this component results in the IF amplifier remaining at full gain. In the internal video mode the resistor must be disconnected to achieve the auto-VCR mode. Input Signal 50 Hz 60 Hz None Don’t care Don’t care Don’t care Pin 9/10 Pin 25 9.5 9.5 0.3 9.5 9.5 9.5 Pin 28 50 Hz 60 Hz None 50 Hz 60 Hz None Pin 18 LOW LOW LOW HIGH HIGH HIGH Pin 14 12 9 0.3 12 9 12 pin 17 HIGH: VCR mode fast time constant; ungated pin 17 n.c.: auto VCR mode pin 17 LOW: TV mode slow time constant; gated pin 18 LOW: internal video pin 18 HIGH: external video |
Numéro de pièce similaire - TDA4504B |
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Description similaire - TDA4504B |
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