LM1253A National Semiconductor, LM1253A Datasheet - Page 10

• Manufacturer Part Number: LM1253A
• Description: Monolithic Triple 180 MHz I2C CRT Pre-amp With Integrated Analog On Screen Display (OSD) Generator
• Manufacturer: National Semiconductor

www.national.com
Pin Descriptions
Pin 13 — Clamp A positive going clamp signal is input on
this pin. Using this signal black level clamping of the video is
carried out directly on the input video that is AC coupled into
the high impedance preamplifier input, thus eliminating the
need for additional black level clamp capacitors. Figure 29
shows the external schematic of pin 13, Figure 17 shows the
internal schematic. An optional capacitor to ground may be
needed if noise interferes with the clamp signal.
(Continued)
FIGURE 8. Effect of ABL Voltage on V
10
Pin 14 — H Flyback H Flyback is an analog signal input from
the monitor horizontal scan. HBLANK is a digital signal de-
rived from the horizontal flyback pulse as shown in Figure 9 .
An optional capacitor and/or resistor to ground may be
needed if noise interferes with the H Flyback signal.
The horizontal flyback from the monitor must be a clean sig-
nal. There should be no ringing or other noise on the flyback.
DS101265-70
OUT