µPC1830

16

5.3 Matrix Section

(1) Input signal

•

Brightness input signal

After coupling by a capacitor (0.22

pin (pin 16).

•

Color difference input signal

After coupling by a capacitor (0.22

(pins 18 and 19).

(2) Y, R-Y and B-Y input clamp circuit

Clamps Y, R-Y and B-Y signals when the voltage of the clamp pulse input pin (pin 22) is 2.8 V or higher.

Input a clamp pulse to the clamp pulse input pin (pin 22) in synchronization with the burst section of an input signal

as shown in Figure 5-3.

In the application circuit example, adjust the position of the clamp pulse by DELAY (

µPD4538B external variable

resistor: 10 k

Ω) and the clamp pulse width by PD (

µPD4538B external variable resistor: 10 kΩ).

Figure 5-3. 22-Pin Input Clamp Pulse Waveform

(3) Amplification color control circuit

Adjusts the amplitude of a color difference signal input to the R-Y input pin (pin 18) and B-Y input pin (pin 19) according

to the voltage of the color control pin (pin 20). This controls the color density on the screen.

When using a matrix, adjust the color density mainly using this color control and fix the voltage of the subcolor control

pin (pin 37) at 2 V (TYP.).

The control characteristic is shown in Figure 5-4.

Video signal

Composite

video input

22-pin input

clamp pulse

Burst signal

Clamp operates at 2.8 V or higher.