Analog Angle Article

Linear Tech’s LTC2261 ADC does 14 bits at 125 Msps and 127 mW; offers varied digital-side choices

Milpitas, Calif.—Reaching their 1 mW/Msps goal, the LTC2261 top-line member of a new analog/digital converter (ADC) family from Linear Technology Corp. provides 14-bit conversions at up to 125 megasamples/sec (Msps). The pipelined converter (5 cycle latency) dissipates 127 mW, drawing 70 mA from a 1.8 V analog supply (1.2 to 1.8V for the digital side), and 9 mW in nap mode and 0.5 mW in sleep mode. The converter family targets portable applications such as medical imaging, non-destructive testing (NDT), software defined radio (SDR), and instrumentation.

Static specifications for the highest-performance converter, include ±1 LSB integral nonlinearity (INL) and ±0.3 dB differential nonlinearity (DNL); dynamic performance specifications include signal-to-noise ratio (SNR) of 73.4 dBc and spur free dynamic range of 85 dBc, commensurate with the needs of many signal-processing designs. Input signal range is selectable at 1.0 or 2.0 Vp-p , full power bandwidth is 800 MHz, and aperture jitter (critical to dynamic performance) is 0.17 psec.

In addition to the analog-side performance, the ADCs offer a wide variety of user-programmable options for the digital output, all set via an SPI port. Among the choices are:

  • Full rate CMOS using 14 data lines
  • Double data rate (DDR) CMOS, 7 data lines
  • DDR LVDS, 14 data lines, for reduced digital noise
  • Straight binary or twos complement data coding
  • Selectable LVDS output current (1.75 to 4.5 mA), to match output current to the load, while minimizing power dissipation
  • Internal 100-ohm resistors which you can switch in, to absorb reflections due to impedance mismatch at the receiver
  • A data randomizer which scrambles the output bits via an exclusive-OR circuit, to reduce noise coupling from major signal transitions and improve SFDR (the data receiver, of course, must do a reverse XOR to unscramble them); LTC claims this can reduce residual tones caused by digital feedback by 10-15 dB

Price and availability : LTC is offering a total of six pin-compatible ADCs in the family, spanning 12 bits at 80, 105, and 125 Msps, and 14 bits at 80, 105, and 125 Msps. Pricing for the 6×6 mm QFN-40 ICs, in commercial and industrial temperature ranges, begins at $9.50 each (1000 piece lots). Samples are available now, with full production in December. LTC is also offering demonstration boards for evaluation and assessment.—Bill Schweber.

0 comments on “Linear Tech’s LTC2261 ADC does 14 bits at 125 Msps and 127 mW; offers varied digital-side choices

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.