Electronic Design

Fast 14- & 16-Bit ADCs For Comm & Instrument Apps

The multicarrier, multimode receivers in next-generation cellular infrastructure equipment will need analog-to-digital converters (ADCs) with higher spurious-free dynamic range (SFDR) and signal-to-noise ratio (SNR). This is to help deal with the basestation near-far problem (capture of weak signals in the presence of stronger signals in the same frequency band). Fortunately, equipment designers can look to Analog Devices' 14-bit AD9455 ADC. With input frequencies of up to 300 MHz, its 80-dBc SFDR is 10 dB better than today's best communications ADCs. Plus, at 225 MHz, its SFDR tops 85 dBc.

In the AD9455, Analog Devices also reduced aperture jitter by factors of five or six to 50 fs. This resulted in an SNR slashed to 72.5 dBfs at 300 MHz and 73.5 dBfs at 225 MHz. The combination of 14-bit resolution and low noise makes it possible to capture the input signal with fewer samples.

Other key specs include ±0.2-LSB (typical) differential nonlinearity (DNL) and ±0.6-LSB integral nonlinearity (INL). The AD9445 has an on-chip reference and track-and-hold, as well as parallel low-voltage differential signaling (LVDS) outputs. Power dissipation is 2.3 W. A 105-MHz version is available, too.

With another 2 bits of resolution and 10 times the maximum sample rate of other 16-bit ADCs, ADI's 105-Msamples/s AD9446 suits high-performance test and measurement applications that use digital time sampling for frequency and time domain analysis, along with military and aerospace communication systems and high-end medical devices. SFDR is 85 dBc and SNR is 80 dBfs at Nyquist. DNL is ±0.5 LSB, and INL is ±3 LSB. Power dissipation is 2.3 W. An 80-MHz version with even higher specs at Nyquist is available.

The 14-bit, 125- and 104-Msamples/s AD9445-125 and AD9445-105 are sampling now. Production quantities will be available in September for $59.50 and $49.30, respectively, in 1000-unit quantities. The 16-bit, 105- and 80-Msamples/s AD9446-105 and AD9446-80 also are sampling, with the same target production date. They cost $79.90 and $72.25 each, respectively.

Analog Devices
www.analog.com

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