GENERAL DESCRIPTION
The TDA3508 is an integrated circuit which performs video control functions in a PAL/SECAM decoder for negative colour difference signals −(R−Y) and −(B−Y). The required input signals are luminance and colour difference and a 3-level sandcastle pulse for control purposes. Linear RGB signals can be inserted from an external source. RGB output signals are available for driving the video output stages. The circuit provides automatic cut-off control of the picture tube.

FEATURES
• Capacitive coupling of the colour difference and luminance input signals with black level clamping in the input stages
• Linear saturation control acting on the colour difference signals
• (G−Y) and RGB matrix
• Linear transmission of inserted signals
• Equal black levels for inserted and matrixed signals
• Three identical channels for the RGB signals
• Linear contrast and brightness controls, operating on both the inserted and matrixed RGB signals
• Peak beam current limiting input
• Clamping, horizontal and vertical blanking of the three input signals controlled by a 3-level sandcastle pulse
• Three DC gain controls for the RGB output signals (white point adjustment)
• Emitter-follower outputs for driving the RGB output stages
• Input for automatic cut-off control with compensation for leakage current of the picture tube.