General Purpose Sync SeparatorsThe devices extract the timing information from composite video signals with scan rates from 15 to 130kHz

Overview:

The GS1881, GS4881 and GS4981 are general purpose sync separators for use in a wide variety of video applications.

The devices extract the timing information from composite video signals with scan rates from 15 to 130kHz.

The GS1881 is a drop-in replacement for the industry standard LM1881 with much improved performance. The device generates composite sync, vertical sync, back porch and odd/even field signals. The GS4881 is identical to the GS1881 but features a noise immune back porch pulse which maintains a constant H rate during the vertical interval. The GS4981 is identical to the GS4881, except that it provides horizontal sync in place of the odd/even output.

All three devices feature a self-adjusting windowing circuit for noise immunity, which synchronizes to H rate. This windowing circuit determines the odd or even field in the GS1881 and GS4881, gates the back porch pulse in the GS4881 and GS4981, and generates the horizontal sync output in the GS4981.

The devices feature an improved input stage which ensures that the input signal is sliced at a predictable point due to well-controlled input clamp discharge current and sync slicing level. A missing pulse detector enables the devices to recover quickly from impulse noise disturbances by temporarily increasing the clamp discharge current by roughly ten times. The input stage will operate with signals from 0.5 to 4 volts peak to peak with a 5 volt supply.

The GS1881, GS4881 and GS4981 also feature a predictable vertical output pulse width with a default trigger for non-standard video signals. All three are available in commercial and industrial temperature ranges and are packaged in both DIP and SOIC.