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Multiplexer packs VGA switching in a single chip

Posted: 08 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Maxim? VGA? analog? IC? switch?

Maxim Integrated Products has introduced the MAX4885, an analog switch that promises to perform the entire VGA video switching task: R, G, B, H/V and the DDC (I2C) switching/translation.

According to the company, previous solutions required three ICs, discrete FETs, and ESD-protection diodes to accomplish these tasks, but the new device saves board space and 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 device switches the signals from one source and connects them either to an internal connector or through to a docking station. Or, it can be used in a monitor or projector to select one of two inputs.

Maxim said the new product is the first device to simplify VGA switch implementation into a single-chip solution. It gives customers >500MHz broadband width and 3-state capability for achieving high 4:1 mux ratios.

"Video design engineers can now simplify their VGA design with our integrated 3-channel RGB video switch, H/V sync signal switches, and DDC signal switches. They can also incorporate TTL-compatible logic-level translators as well as robust 8kV ESD protection," said Jeff DeAngelis, director of business management for Maxim's Interface, Switch, and Protection business unit.

Compared to traditional analog-RGB implementation, Maxim said its new analog switch uses 25mm2 of board space, 50 percent less than the previous 50mm2 norm. Also, this new part costs 25 percent to 30 percent less than its multichip predecessors, the company added.

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

According to Maxim, 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 device can operate from a single 5.0V supply or a 50V and a second supply (usually the available 3.3V), which is used for clamping the dangerous higher voltages to prevent damage to the signals in the DDC path, the company explained.

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.

Target applications for the new analog switch are laptop computers, consumer video products, digital projectors, computer monitors, servers, and other industrial PC-related peripherals. In notebook applications, the device will be placed on the motherboard and located between the standard VGA connector and the multi-pin docking station connector. It handles all the necessary switching between the docking station and the VGA connector, Maxim said.

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

The MAX4885 comes in a 5-by-5mm, 32-pin TQFN package. The device is specified over the -40C to 85C extended temperature range. Pricing begins at $1.25 (1,000-up, FOB USA) and samples are already available.

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