RC6120

The RC6120 is the basis of an NTSC and PAL chroma subcarrier re-generation capability. The wide burst-gate generator enables the phase comparator during the back porch interval. The phase of the VCXO output is compared to that of the chroma signal reference burst. The phase error is sampled in the center of the burst, extemally hltered by the loop filter and applied to the VCXO to correct its phase.  In NTSC mode both sample/hold circuits sample simultaneously. In PAL mode they sample on alternate lines and the phase errors, of nominally $450 from the VCXO signal, are summed to form the VCXO control signal. A lock detector measures the subcarrier phase error and indicates phase lock status of the loop. This output of RC6120 can also be used to control the speed (bandwidth) of the loop filter. If a burst is present, the sampling pulse sequence is generated by the Burst Pick-off Sample Pulse Generator and Sample Logic.

The features of RC6120 can be summarized as (1)NTSC and PAL subcarrier regeneration; (2)adapts to incorrect burst amplitude and position; (3)rapid lock and long time constant for noise averaging; (4)locked indication if <10° phase error; (5)dual ±10V supplies; (6)CMOS compatible logic.

The absolute maximum ratings of RC6120 are (1)positive power supply voltage (Vgg): -02(min)/11(max)V; (2)negative power supply voltage (VEE): 02(min)/-11(max)V; (3)operating temperature: 70 °C; (4)storage temperature: -40 to 125°C; (5)junction temperature:150°C(max); (6)lead soldering (10 seconds): 300°C(max); (7)package thermal resistance (JA): 75°C/W (note: Functional operation under any of these conditions is NOT implied. Performance and reliability are guaranteed only if Operating Conditions are not exceeded.)