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CompactPCI-based PXI module conveys 64 DAC channels

Posted: 24 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:kineticsystems? dac card? digital-to-analog converter card? compactpci? pxi?

Board maker KineticSystems has a new D/A (digital-to-analog) converter card that packs no less than 64 channels of D/A output in a single-width 6U-sized CompactPCI form-factor for PXI (pci extensions for Instrumentation). It's priced at about $2,750.

A word about PXI. It's based upon the CompactPCI bus, with data transfer rates up to 132MHz. PXI is optimized for measurement, control, and automation of test systems, and KineticSystems's PXI data-acq products use a modular architecture to provide integrated timing and synchronization between instruments. Dubbed the CP266, this new CP266 plug-in joins the company's growing family of data acquisition and ATE (automated test equipment) products for CompactPCI/PXI, as well as VXI, and stand-alone data-acq platforms.

16-bit resolution

With 16-bit resolution and 10-V full-scale (FS) output, the CP266 can stimulate DUTs (devices under test) for ATE. In addition, the power-up state of its analog outputs can be set to independent user-defined values to provide non-zero voltage settings on application of power.

The analog outputs are available at a single 68-pin SCSI II shielded connector (for a 32-channel option), or a pair of 68-pin SCSI II shielded connectors for the full 64-channel implementation. The channel update rate is 2ms, and each output is accurate to within 1mV. Paired output signals are provided to eliminate ground offset effects.

Plug-and-play drivers

Similar to the company's VXI counterpart called the V266, the CP266 ships with plug-and-play drivers for configuration and use. Application examples, including source code, are also provided to illustrate basic functions. In use, data values for each channel are written to a 16-bit wide, dual-port memory. It's sequentially scanned, and the values are then applied to a single 16-bit DAC. The DAC output is then MUXd to separate sample-and-holds. There's one for each channel.

Lowpass filtering

The outputs of these circuits pass through active 2-pole lowpass (500Hz) Bessel filters. The Bessel filters provide optimum step response. Since the voltage outputs of all circuits are accurate to within a millivolt of each other, only one offset and one gain pot are needed to adjust the DAC. Nothing could be simpler!

Data can be written to or read from the CP266 in either offset binary or two's complement format. During power-on, the module initiates a sequence to restore the memory contents to user-defined values or to the zero default.

- Alex Mendelsohn


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