GS1881 Ver la hoja de datos (PDF) - Gennum -> Semtech

Número de pieza

componentes Descripción

Fabricante

GS1881

Monolithic Video Sync Separators

Gennum -> Semtech 

5. Application Notes

5.1 Choosing the Appropriate Input Capacitor to

Optimize Slicing Level and Hum Rejection

The video designer can adjust the slicing level by choosing the value of the input

coupling capacitor. The relationship between slicing level and input coupling capacitor

is described by the following equation:

∆VSLICE =

IDIS

CC

∆T

= VDROOP

where:

IDIS = clamp discharge current = 11 μA

∆T = TLINE - TSYNC = (63.5 μs - 4.7 μs)

CC = input coupling capacitor

Figure 5-1 is a graphical representation of this equation and Figure 5-2 and Figure 5-3

show the input video waveforms for 0.1μF and 0.01μF input capacitors respectively. The

advantage in choosing a smaller input coupling capacitor, is increased hum rejection as

the following analyses illustrates.

137

127

117

107

97

87

77

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

INPUT COUPLING CAPACITOR (μF)

Figure 5-1: Slicing Level vs Input Coupling Capacitor

GS1881, GS4881, GS4981 Monolithic Video Sync

Separators

Data Sheet

6926 - 5

November 2009

20 of 29

Proprietary & Confidential

Share Link: