Mixed Signal/Analog

Analog Devices' High-Speed Multi-Channel ADCs Reduce System Board Space

19th November 2008
ES Admin
Analog Devices has introduced a pair of four-channel 12-bit analog-to-digital converters (ADCs) that use 50 percent less printed-circuit-board surface area than other ADCs in their class. The AD9239 and AD9639 quad analog-to-digital converters require only eight pins and traces, compared to as many as 26 in competing dual-channel devices, which yields space savings in high-speed signal processing applications, including cable infrastructure and point-to-point wireless communications equipment and spectrum analyzers. As part of a complete receive-path signal chain solution, the AD9239 and AD9639 quad ADCs are compatible with ADI’s variable gain amplifiers, including the AD8372 and AD8376.
The 250-MSPS (mega-sample-per-second) AD9239 incorporates an efficient packetized output scheme, while the 210-MSPS AD9639 supports a JESD204-compliant output scheme. Both ADCs feature on-chip PLL (phase-locked loop) and input buffer circuits, which are designed for low cost, low power, small size, and ease of use. The new ADCs require a single 1.8-V power supply, dissipating 1.5 W in normal mode and 145 mW per channel (typical) when standby-mode is enabled with the digital link remaining in operation. The new devices are also the first high-speed ADCs to feature an on-chip temperature sensor, which allows engineers to conduct thermal monitoring for optimized system operation. The quad ADCs offer excellent noise performance and achieve SNR (signal-to-noise ratio) of 65 dBFs, SFDR (spurious-free dynamic range) of 77 dBc and an ENOB (effective number of bits) of 10.5, all at an 85-MHz input frequency.

The AD9239 and AD9639 support an LVDS (low-voltage differential signal)-compatible sample-rate clock input and provide four serial digital output streams with coded data from each ADC channel. Clock information is also coded into each serial stream so that the receiving logic can extract the necessary clocking information. The AD9239 and AD9639 are available with ADI’s VisualAnalog™ evaluation and ADIsimADC™ behavioral software modeling tools.

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