Linear Technology announces a 16-bit, 105Msps ADC for digital communication between high speed ADCs and FPGAs. The LTC2274’s 2-wire serial interface reduces the number of data input/output (I/O) lines required between a 16-bit ADC and the FPGA from 16 CMOS or 32 LVDS parallel data lines to a single, self-clocking, differential pair communicating at 2.1Gbps, freeing up valuable FPGA pins. Serial data communications offers simplified layout, and requires less board area for routing, while providing the flexibility to route across analog and digital boundaries.
The LTC2274 output data is serialized according to the JEDEC serial interface specification for data converters (JESD204) using 8b10b encoding, and is compatible with many FPGA high speed interfaces including Xilinx’s Rocket IO, Altera’s Stratix II GX I/O and Lattice’s ECP2M I/O. At 2.1Gbps, the LTC2274 offers a fast serial interface. For high-sensitivity receiver applications, the device provides an internal transparent dither circuit that improves the ADC’s SFDR response well beyond 100dBc for low level input signals. To avoid any interference from the serial digital outputs, an optional data scrambler is available to randomize the spectrum of the serial link. Serial test patterns are also incorporated to facilitate testing of the serial interface.
While the LTC2274 may be operated at a maximum sampling rate of 105Msps, the internal PLL may be configured to lock at one of three different sample rate ranges. An on-chip clock duty cycle stabilizer circuit has been implemented to facilitate non-50% clock duty cycles. Separate shutdown pins for the analog and digital sections are provided to conserve power. The chip offers signal to noise ratio (SNR) performance of 77.5dB and spurious free dynamic range (SFDR) of 100dB at baseband. Jitter of 80fs RMS enables undersampling of input frequencies up to 500MHz with excellent noise performance. The ADC consumes 1.3W from a 3.3V analog supply.
The device serial output allows it to fit in a 6mm x 6mm QFN-40 package, less than half the size of 16-bit ADCs with parallel outputs. In addition to the 16-bit, 105Msps LTC2274, pin-compatible 80Msps and 65Msps versions will be releasing this summer. Production quantities of the LTC2274 will be available in July in both commercial and industrial temperature grades. Demonstration boards and samples are available.
