TDA4570

Chrominance part
` Gain controlled amplifier with operating point control stage
` ACC (automatic chrominance control) with sampled rectification during burst-key signal
` Blanking circuit for the colour burst signal
Oscillator and control voltage part
` Voltage controlled reference oscillator for double subcarrier frequency
` Divider stages which provide the correct 90° phase between -(R-Y) and -(B-Y) reference signals for the  emodulators
` Phase comparator which controls the frequency and phase of the reference oscillator and compares the (R-Y) reference with the burst pulse
` HUE control stage provides phase shifting via the combined service and hue control input (pin 11)
` Identification demodulator provides a positive-going identification signal at pin 14 for NTSC signals and acts as the automatic colour killer
` Two-function service switch:
position one (V14-3 < 1 V): switches the colour-ON and switches the hue control and burst for the PLL oscillator-OFF, allowing the adjustment of the reference oscillator
position two (V14-3 > 5 V): switches the colour-ON, the hue control OFF and allows the output signal to be bserved
` Sandcastle pulse detector for burst-gate, horizontal and horizontal/vertical blanking pulse detection. The vertical art of the sandcastle pulse is used for the internal colour-ON and colour-OFF delay
` Pulse processing part for the prevention of premature switching ON of the colour. The colour-ON delay, two or hree field periods after identification of the NTSC signal, is achieved by a counter.
When there is no identification voltage present the colour is switched OFF immediately or, at the most, one field  eriod later.
Demodulator part
` Two synchronous demodulators for the (R-Y) and (B-Y) signals, which incorporate stages for the blanking during ine and field flyback
` Internal filtering of the residual carrier in the demodulated colour difference signals
` Colour switching stages controlled by the pulse processing part in front of the output stages
` The output stages for (R-Y) and (B-Y) signals are low resistance n-p-n emitter followers
` Separate colour switching output

The TDA4570 is an integrated 3,58 MHz or 4,43 MHz NTSC decoder. It is pin sequence compatible with multi-standard
decoder TDA4555 and pin compatible with the PAL decoder TDA4510.