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12-Bit ADCs for WiMAX

From National Semiconductor come two 12-bit 170M sample/sec ADCs(analogue-to-digitalconverters) and a 14-bit, 155M sample/sec ADC, each with a full-power bandwidth of 1.1 GHz. National designed the ADCs, which are available in dual-data-rate, LVDS (low-voltage-differential-signalling) and CMOS output options, for WiMAX and 3G wireless-communications applications. In high-IF (intermediate-frequency)-sampling receiver applications, the 1.1 GHz bandwidth provides high SFDR (spuriousfree- dynamic-range) and SNR (signal-tonoise- ratio) performance that extends beyond 250-MHz input frequencies. This enables the system designer to digitise the signal at the first IF, eliminating a downconversion stage.

The 12-bit ADC12C170 features parallel CMOS outputs, and the 12-bit ADC12V170 has dual-data-rate, parallel- LVDS outputs. The ADC12C170 offers a 84.1-dB SFDR, and the ADC12V170 83 dB. The ADC14V155 has an SFDR of 85 dB and an SNR of 69.5 dB at an input frequency of 238 MHz.

The devices employ a differential, pipelined architecture and operate in single- ended- or differential-clock modes. At an input frequency of 70 MHz, the ADC12C170 provides a 85.4-dB SFDR and a 67.2-dB SNR, while the ADC12V170 provides a 85.8-dB SFDR and a 67.2-dB SNR. The ADC12C170 typically consumes 715 mW, and the ADC12V170 781 mW. Both ADCs operate from a 3.3V supply and include a power-down feature to reduce power consumption to 5 mW. The ADC14V155’s dynamic performance and linearity at high IF allow for the consolidation of signal paths, enabling the migration from a single-carrier architecture to a multicarrier approach where a single ADC digitises several carriers. The device’s lowjitter front-end allows the digitisation of high-frequency inputs up to 450 MHz. The ADC14V155 operates from a 3.3V supply and typically consumes 951 mW. It offers a power-down feature to reduce power consumption to 15 mW, while a separate 1.8V supply for the digital interface allows low-power operation with reduced noise. The ADC14V155 is supplied in a 48-pin LLP package.

The 12-bit ADC12C170 and 12-bit ADC12V170 are $39.20, and the 14-bit ADC14V155 sells for $67.10 (1000).

National Semiconductor, www.national.com