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ADC offers highest SFDR above 250MHz input frequencies

Posted: 23 Aug 2007     Print Version  Bookmark and Share

Keywords:ADCs  WiMAX  3G  wireless communications applications 

National Semiconductor Corp. has launched two 12bit 170MSps ADCs and a 14bit, 155MSps ADC, each with a full-power bandwidth of 1.1GHz. Available in dual-data rate, LVDS and CMOS output options, the ADCs target WiMAX and 3G wireless communications applications.

In high intermediate frequency (IF) sampling receiver applications, the 1.1GHz bandwidth capability of these ADCs provide high spurious free dynamic range (SFDR) and SNR performance that extends beyond 250MHz input frequencies. This enables the system designer to digitise the signal at the first IF, thereby eliminating a down conversion stage, which reduces component count and system power, said National.

The 12bit ADC12C170 with parallel CMOS outputs and 12bit ADC12V170 with dual-data rate, parallel LVDS outputs are said to offer the industry's highest SFDR above 250MHz input frequencies. At an input frequency of 70MHz, the ADC12C170 provides 85.4dB SFDR and 67.2dB SNR, while the ADC12V170 provides 85.8dB SFDR and 67.2dB SNR. Compared to competitive devices, the ADC12C170 at 84.1dB offers 5.5dB better SFDR and the ADC12V170 at 83dB offers 3.8dB better SFDR at an input frequency of 250MHz. These characteristics make them suitable for digital pre-distortion techniques to improve power amplifier efficiency in base station applications.

The ADC12C170 operates from a 3.3V supply and typically consumes 715mW, while the ADC12V170 typically consumes 781mW. Both ADCs include a power-down feature to reduce power consumption to 5mW.

At 1.1GHz, the ADC14V155 delivers 57 percent higher full-power bandwidth than competing 14bit ADCs. The device also provides an SFDR of 85dB and SNR of 69.5dB at an input frequency of 238MHz. In addition, the device's low-jitter front-end allows the digitisation of high frequency inputs up to 450MHz. The 14bit ADC operates from a 3.3V supply and typically consumes 951mW. It offers a power-down feature to reduce power consumption to 15mW, while a separate 1.8V supply for the digital interface allows low-power operation with reduced noise.

Supplied in 48-pin LLP packages, the 12bit ADC12C170 and 12bit ADC12V170 are priced at Rs.1585.87 ($39.20) and the 14bit ADC14V155 is priced at Rs.2714.08 ($67.10)in quantities of 1,000. The devices are available now including samples and evaluation boards.

- Gina Roos

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