DALLAS -- To address higher performance in third-generation, multi-carrier wireless base station designs, Texas Instruments Inc. today launched a new 14-bit resolution digital-to-analog converter that's capable of handling output frequencies up to 400 million samples per second.
The new IC is the first DAC to use low-voltage differential signal (LVDS) interfaces for high-speed data transmission with low noise levels, according to TI. Typically, high-speed DACs use CMOS interfaces, which make high-speed data frequencies difficult to use in board designs, according to TI managers.
With output frequencies up to 400 mega-samples/sec., the new DAC5675 is capable of handling direct digital intermediate frequency (IF) transmissions, which makes it possible to eliminate a mix-up stage from the signal chain in base transceiver stations. The elimination of other devices and functions could result in a 75% reduction in the cost of digital-to-analog conversion, said TI.
"The customer can remove the mixer, filtering, additional amplification in the chain, and just use this DAC at higher frequency," said Robert Remmers, systems engineering manager for TI's Wireless Infrastructure Business Unit in the High Performance Analog Group.
TI said the 14-bit resolution DAC will enables transmission of 3G multi-carrier wideband code-division multiple access (W-CDMA) and it supports additional wireless standards, such as CDMA2000, IS-95, GSM, GPRS, EDGE and IS-136, as well as other digital applications based on QAM and QPSK modulation techniques.
The use of LVDS interfaces instead of CMOS I/O will ease the task of avoiding electromagnetic
interference (EMI) in systems when devices are operating at high frequencies. "All major ASIC processes as well as most FPGA libraries have LVDS interface options," Remmers said.
The new DAC will support of up to four W-CDMA carriers in a single channel. TI said the DAC5675 features a 68 dB W-CDMA adjacent channel power ratio (ACPR) at 150 MHz IF. For multi-carrier narrow-band applications, the DAC5675 provides a low intermodulation distortion (IMD3) of -82 dBc at 100 MHz IF.
While the main focus of the new 14-bit DAC is on cellular base transceiver stations, TI also believes the device will work its way into test and measurement applications for arbitrary waveform generation and communication test equipment. Other applications for the DAC include direct digital synthesis (DDS) and cable modem head-end systems.
Samples of the 14-bit DAC are available now with volume production beginning in December. In quantities of 1,000, the device costs $35 each. The DAC is housed in a 48-lead high-temperature quad flat pack (HTQFP).