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High speed analogue switch

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article image Saves space, reduces costs.

MAXIM Integrated Products, represented by Arrow Electronics , has introduced the MAX4885, a high-speed analogue switch that performs the entire VGA video switching task: R, G, B, H/V, and the DDC (I2C) switching/translation.

Previous solutions required three ICs, discrete FETs, and ESD-protection diodes to accomplish these tasks.

The MAX4885 saves board space, reduces system cost by replacing all these parts with one IC, and provides the ability to switch more than two video sources.

In a typical application, the MAX4885 switches the signals from one source and connects them either to an internal connector or through to a docking station.

Alternatively, the MAX4885 switch can be used in a monitor or projector to select one of two inputs. Typical applications include laptop computers, monitors, projectors, and HDTV receiver/monitors.

One chip does the work of many

Historically analogue-RGB switch implementation required an RGB switch, H/V sync switch, logic-level translators, DDC FETs, and ESD-protection diodes. The MAX4885 is the first device to simplify VGA switch implementation into a single-chip solution.

Compared to traditional analogue-RGB implementation, the MAX4885 uses 25mm2 (package information below), 50% less board space than the prior 50mm2 norm. Also, this new part costs 25% to 30% less than its multichip predecessors.

The achievement is in the integration

By integrating three SPDT, 500MHz analogue switches, 2 SPDT H/V signal switches, 2 SPDT DDC signal switches, 2 TTL compatible logic-level gates, and the ±8kV ESD-protection devices, the MAX4885 provides the customer with a complete 1:2 or 2:1 VGA switching solution. This part is the first device available in the market to address this total function.

The DDC switches are level-shifting n-channel FETs, offering high-voltage protection to sensitive low-voltage circuits. The built-in logic-level shifting of the H/V signals allow a low-voltage graphics chip to interface with the required 5V video TTL-level output.

The MAX4885 can operate from a single +5.0V supply or a +5.0V supply, and a second supply (usually the available +3.3V supply) which is used for clamping the dangerous higher voltages to prevent damage to the signals in the DDC path.

An innovative 3-state feature allows the cascading of multiple MAX4885 ICs. Multiplexing ratios of 4:1, or more, can be achieved to support more than two video sources.

Simplifies switching design for many applications

Target applications for the MAX4885 are laptop computers, consumer video products, digital projectors, computer monitors, servers, and other industrial PC-related peripherals.

In notebook applications, the MAX4885 will be placed on the motherboard and located between the standard VGA connector and the multipin docking station connector. The MAX4885 handles all the necessary switching between the docking station and the VGA connector.

The MAX4885 can also be used in high-resolution analogue video monitors to support multiple incoming signals to source into the display.

Available for design now

The MAX4885 provides customers these unique capabilities in a compact 5mm x 5mm, 32-pin TQFN package. The MAX4885 is specified over the -40°C to +85°C extended temperature range.

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