Converting analog to digital (A-D) and digital to analog (D-A) signals requires different performance levels and very different packaging depending on the application. Here are three new stand-alone A-D converters (ADCs) and two new D-A converters (DACs) that bring out the differences.
10-BIT, 1.5 GSPS A-D CONVERTER
Atmel Corporation AT84AS003TP (http://rbi.ims.ca/4392-541). This 10-bit analog-to-digital converter (ADC) exceeds 8.0 effective number of bits (ENOB) at sampling rates over 1 Gsps. The unit's embedded 1:4 low-voltage differential signaling (LVDS) demultiplexer allows direct interfacing with standard FPGAs. In Nyquist conditions, engineers measured 8.0 ENOB, 58 dB spurious free dynamic range (SFDR) at 1.5 Gsps. The 3 GHz analog input bandwidth allows operation in a second Nyquist zone as well. When sweeping the sampling frequency from 100 Msps to 1.5 Gsps, additional timing or voltage tuning between the ADC and DMUX is not required. Packaging for the AT84AS003TP is a 25 × 35 mm 317-pin enhanced ball grid array, EBGA317. Target applications include upgrading existing systems or new digitizers for digital receivers, test instrumentation, or radar equipment.
DUAL 16-bit D-A CONVERTER SAMPLES AT 1 GSPS
Analog Devices Inc. AD9779 (http://rbi.ims.ca/4392-542). The dual 16-bit DAC achieves a sample rate of 1 GSPS and has typical 159 dBm/Hz noise spectral density (NSD), 88 dBc two tone intermodulation distortion (IMD) (fDAC=800 MSPS, fOUT=100 MHz), and 87 dBc spurious free dynamic range (SFDR) at a 70 MHz output frequency. The device contains on-chip digital interpolation filters with 84 dB stopband attenuation, a digital modulator that allows fDAC/2, fDAC/4, fDAC/8 modulation, and a digital mixer. The dual DACs come in a 100-lead exposed-paddle TQFP package. Target applications include conversion in wireless standards, such as W-CDMA, CDMA2000, TD-SCDMA, and WiMAX.
DUAL 8-BIT D-A CONVERTER
Maxim Integrated Products /Dallas Semiconductor MAX5109 (http://rbi.ims.ca/4392-543). This dual 8-bit DAC has nonvolatile registers and a two-wire interface. Storing the operating modes and output states in the nonvolatile registers, allows the DACs to initialize specified configurations at power-up. At power-down the software decreases the supply current to less than 25 ľA. A software-controlled mute mode sets each DAC or both DACs simultaneously, to their reference low voltage levels. The I2C-compatible, two-wire serial interface operates at a maximum clock frequency of 400 kHz. The dual DAC is available in a 16-pin QSOP. Applications include ATE calibration, digital gain and offset adjustments, laser biasing, portable instruments, power-amp bias control, and programmable attenuators.
MOTOR CONTROL A-D CONVERTER
Texas Instruments ADS7869 (http://rbi.ims.ca/4392-544). This motor-control front-end includes three 1-Msps (mega-samples-per-sec), 12-bit ADCs with a total of seven sample-and-hold capacitors. The twelve fully differential input channels have gain and offset adjustments for every channel. The digital interface has a serial peripheral interface (SPI) and two parallel modes. In addition, a specialized serial interface with three data lines (100 percent software-compatible VECANA01 mode) allows the unit to interface with most digital signal processors or microcontrollers. To ensure that the analog input of the encoder is held at the same point of time as the counter value during position sensor analysis, the unit has two up-down counters. The motor control ADC is packaged in a TQFP-100.
8-CHANNEL 200 KPS A-D CONVERTER
Linear Technology Corporation LTC1867 (http://rbi.ims.ca/4392-545). This 16-bit, 8-channel ADC targets low power applications and draws 2.7 mW max from 3V supply at full speed. The unit provides 16-bit no missing codes and ą2 LSB max integral nonlinearity (INL) over temperature. With low-power applications in mind, engineers included a sleep mode and an automatic nap mode between conversions, which typically reduces the power to 0.9 mW at 50 ksps. The 8-channel multiplexer allows single-ended or differential inputs in either unipolar or bipolar conversion modes. The unit is offered in a 16-pin narrow SSOP package. Applications include industrial process control, high-speed data acquisition, battery operated systems, multiplexed data acquisition systems, and imaging systems.