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wirelessZONE Products for the week of August 3, 2009
Linear Technology Says…
LTC6412: 800 MHz VGA: 31 dB Analog Control And 35 dBm OIP3 From 3.3 V Rail
Linear Technology introduced the LTC6412, an 800MHz analog-controlled variable gain amplifier (VGA) with outstanding noise and distortion performance, gain conformance, and gain flatness. The device’s gain control is highly linear. With a guaranteed maximum conformance error of only 0.45dB, the LTC6412 offers a significant improvement over competing solutions.
The LTC6412 is optimized for operation from 1MHz to 500MHz and provides continuous gain adjustment from -14dB to 17dB. Third-order output intercept point (OIP3) is 35dBm at 240MHz across all gain settings. The LTC6412 also achieves a constant output noise level over the entire gain range, with a noise figure (NF) of just 10dB at the maximum gain setting. This results in a constant SFDR characteristic, remaining at greater than 120dB at 240MHz over the full gain control range. The LTC6412 is therefore ideal for use in automatic gain control (AGC) in receiver IF chains.
The device’s gain is controlled with either a positive or negative slope control voltage. Using negative gain slope mode, the gain control slope is approximately -32dB/V at 140MHz, with a control range of 0.1V to 1.1V.
The LTC6412 consumes just 110mA on a 3.3V supply, enabling a low power, compact solution when paired with other low voltage mixers such as the LT5557, ADC drivers such as the LTC6400 and LTC6416, and ADCs such as the LTC2208. It also includes a shutdown pin, reducing the current consumption to below 1mA for power-down or sleep modes.
EN-Genius Says…
Linear just about says it all in the press release. I am, however, very surprised at the low-key approach they have taken to the part. When I was first shown it – some months ago – I recognized a solution that I have looked for so many times in my engineering life…
What is staggering about the LTC6412 is the gain linearity over frequency. Here, for the first time, is a part that you can throw a band of signals through, like 10 MHz to 200 MHz, and actually get a decent result at the output over a 31 dB gain range. And, of course, I love that the control is analog.
I would take issue with Linear’s “Typical Application” on the front page of the data sheet showing an LTC6412 driving an LTC6400-8 op amp and an LTC2208 ADC. The LTC2208 is a 16 bit 150 Msample/s part and the LTC6412 with a 10 dB noise figure at maximum gain just doesn’t cut the mustard for full 16 bit operation.
The total supply current of the LTC6412 at 3.3 V is a typical 110 mA. Typical PSRR at both maximum and minimum gains is 53 dB.
This is a sleeper part. It will provide a major number of breakthroughs in receiver and distribution applications, most of which I cannot fully imagine just yet. Once volume starts moving it will be a huge success for Linear. Watch for follow-on parts as the applications begin to sort themselves out.
The LTC6412 is in production in QFN-24 priced at $4.69 in 1000-piece lots.
Data Sheet
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