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TDA4655 Scheda tecnica(PDF) 6 Page - NXP Semiconductors |
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TDA4655 Scheda tecnica(HTML) 6 Page - NXP Semiconductors |
6 / 17 page June 1993 6 Philips Semiconductors Preliminary specification Generic multi-standard decoder TDA4655 demodulated signal. The result is an identification signal (PIDT, pin 15) that is positive for a PAL signal in PAL mode, for a SECAM signal in SECAM mode and for a PAL signal in NTSC 4.4 mode. If PIDT is positive in SECAM mode, the scanner switches back to the PAL mode in order to prevent a PAL signal being erroneously identified as a SECAM signal (PAL priority). If then PIDT is not positive, the scanner returns to SECAM mode and remains there until PIDT is positive again. In the event of a field frequency of 60 Hz the signal can not be identified as a SECAM signal, even if PIDT is positive. In this event the scanner switches forward in the NTSC 3.5 mode. If the H/2 signal has the wrong polarity, the identification signal is negative and the H/2 flip-flop is set to the correct phase. The third demodulator operates in NTSC mode and is active during the burstkey pulse. The resulting identification signal (NIDT, pin 14) is positive for PAL and NTSC 4.4 signals in NTSC 4.4 mode and for NTSC 3.5 signals in the NTSC 3.5 mode. The reference signal has the (B −Y) phase. The two identification signals allow an unequivocal identification of the received signal. In the event of a signal being identified, the scanning is stopped and after a delay time the colour is switched on. The standard outputs (active HIGH) are available at the pins 20, 21, 22 and 23. During scanning the HIGH level is 2.5 V and when a signal has been identified the HIGH level is switched to 6 V. The standard pins can also be used as inputs in order to force the IC into a desired mode (Forced Standard Setting). Sandcastle detector and pulse processing In the sandcastle detector the super sandcastle pulse (SC) present at pin 24 is compared with three internal threshold levels by means of three differential amplifiers. The derived signals are the burstkey pulse, the horizontal blanking pulse and the combined horizontal and vertical blanking pulse. These signals are processed into various control pulses required for the timing of the IC. Bandgap reference In order to ensure that the CD output signals and the threshold levels of the sandcastle detector are independent of supply voltage variations a bandgap reference voltage has been integrated. LIMITING VALUES In accordance with the Absolute Maximum Rating System (IEC 134). THERMAL RESISTANCE SYMBOL PARAMETER CONDITIONS MIN. MAX. UNIT Tstg storage temperature −25 +150 °C Tamb operating ambient temperature 0 +70 °C Vp supply voltage − 8.8 V Ptot power dissipation without load − 330 mW V24 voltage at pin 24 Imax =10 µA − 15 V voltage at all other pins Imax = 100 µA − VP + Vbe V SYMBOL PARAMETER THERMAL RESISTANCE Rth j-a thermal resistance on printed-circuit board from junction to ambient in free air (without heat spreader) SO 24 90 K/W SDIL 24 70 K/W |
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