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Maxim > Design Support > Technical Documents > Reference Designs > Analog Switches and Multiplexers > APP 4370

Keywords: VGA switching, VGA signals, switching VGA signals

REFERENCE DESIGN 4370 INCLUDES: Tested Circuit Schematic Description

Reference Design for Switching VGA Signals in a

Laptop

Mar 17, 2009

Abstract: This application shows how the MAX4885E low-capacitance VGA switch can be used to

perform the switching function in a laptop computer. The MAX4885E draws nearly zero current, fits into a

4mm x 4mm package, and incorporates most of the switches and active components used in a discrete

business-oriented laptops need to work with a docking station and with the vast number of existing

projectors. Nearly all projectors have a VGA port which is the only common way for a typical user to

hook up a laptop. Although digital connections such as DVI™ and HDMI™ are appearing, the vast

majority of projectors still only support VGA.

The requirement to support VGA through the docking station and the VGA port will likely continue for

many years, until one digital standard fully replaces the ubiquitous blue VGA connector on the laptop.

Maxim introduced the MAX4885E low-capacitance VGA switch to perform that switching function.

The MAX4885E draws nearly zero current, fits into a 4mm x 4mm package, and incorporates most of the

switches and active components used in a discrete implementation. All device outputs are protected to

±15kV HBM (Human Body Model), so that the designer can eliminate many ESD components, reduce

the quality of the waveform is preserved. Some designers use the older "bus switches" with 12pF of

capacitance which compares to the 6pF for the MAX4885E. Those older bus switches, moreover, need

ESD diodes which reduce the bandwidth further and add cost to the system.