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Video amp with load detect saves up to 75% power

Posted: 04 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:video amplifier? load detection? power consumption?

Maxim Integrated Products has released the MAX9516 video amplifier, which detects and reports the presence of a video load and reduces power consumption when the load is not present. Using Maxim's latest 1.8V technology, the MAX9516 lowers power consumption 75 percent below other solutions.

The MAX9516 leverages the company's DirectDrive technology to generate a clean, internal negative supply. By combining the internal negative power supply with the external positive 1.8V supply, the device drives a 2Vp-p video signal into a 150? load.

Operating at the 1.8V single power supply, the MAX9516 only consumes 6mW quiescent power and 12mW average power while a typical competitive video filter amp operating at 3.3V burns at least 46mW of average power. If customers use the 1.8V digital supply, they can eliminate the analog supply, an added convenience and can simplify designs. Offered in a 2mm x 2mm microDFN package, the MAX9516 is suitable for portable applications like digital still cameras, digital camcorders, and cellphones.

Detection convenience
Traditionally, video amplifiers do not have video load detection. Customers would need an external circuit or a specialized video connector to detect the presence of a video load. However, these can only detect whether a cable has been connected to the device, and cannot determine if there is an actual video load at the other end of the cable. The specialized connector requires more board space and is more costly. The availability of such connectors can be limited as well.

The MAX9516 provides customers with an integrated solution to the problem. With built-in load detection and reporting feature, the MAX9516 detects a 75? video load. When the load is not present, the MAX9516 automatically places itself in a 31?W low-power-consumption state. In addition, the MAX9516 reports a change-of-load status with a LOAD flag, which can be connected to a video encoder or other components to trigger the power on and off.

Power, space savings
If a MAX9516 is used with a video DAC, the power consumption of the video DAC can be reduced. Since the MAX9516 has a high-impedance input, the video DAC's output resistor can be increased by at least four times, from 37.5? nominally to 150?. In addition, the output current of the video DAC can be reduced by a factor of four, because the full-scale input level of the MAX9516 is 0.25Vp-p, whereas the typical full-scale input level is 1Vp-p. With both changes, the output current can be reduced by a total factor of 16.

For the utmost power saving, the supply voltage of the video DAC can be reduced from 3.3V to 1.8V. The MAX9516 makes this circuit modification possible because it accepts a 0.25Vp-p video signal, leaving enough headroom for the DAC output stage. With the drop in both output current and supply voltage, the DAC power consumption is substantially reduced.

In addition, the high PSRR spec (49dB at 100kHz) of the MAX9516 is designed to reject the noise from digital power supplies. Customers can use the digital 1.8V power supply to power these analog video amps and potentially eliminate the analog supply to save space and cost.

For added design flexibility, the MAX9516 supports DC-coupled inputs and can be directly connected to the output of a video DAC. The device also features a transparent input sync-tip clamp, allowing AC-coupling of input signals with different DC biases.

To provide additional operational protection, the MAX9516 is offered in the -40Celsius to 125C automotive temperature range. The MAX9516 is priced at 55 cents(1000-up, FOB USA) and is available in a 10-pin microDFN package. Samples and evaluation (EV) kits are available.

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