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300 MHz DDS Chip Empowers 100 MHz PXI Frequency Source

The manufacturer says . . .

ChipCenter's Alex Mendelsohn says . . .

NI Introduces Its Fastest Frequency Source for the PXI Platform Test and design engineers can generate high-frequency sine and clock outputs with the latest addition to the National Instruments line of PXI modular instrumentation. The NI PXI-5404 100 MHz frequency source, the fastest National Instruments source for PXI, can generate sine and clock outputs simultaneously up to 100 MHz with 1.07 µHz resolution and ± 0.2 dB sine-level accuracy. Engineers can use National Instruments new frequency source for flexible clocking options in automated test equipment (ATE) systems as well as for cost-effective sine-wave generation for basic analog stimulus. Its flexible clock output levels address both TTL and CMOS technologies. The simultaneous sine and clock outputs and sine-level accuracy of ± 0.2 dB of this new frequency source make it ideal for coherent sampling in ATE, functional test, and design-validation applications. It features 9 kHz to 100 MHz sine generation and DC to 100 MHz clock generation with the sine amplitude adjustable from 2 V pp to 1 V pp, 12-bit vertical resolution, and sine-wave passband flatness of ± 0.2 dB. With its phase-lock loop, the device can synchronize to the PXI backplane and other devices, such as high-speed digitizers. The NI PXI-5404 frequency source comes with the IVI-compliant instrument driver NI-FGEN, which delivers full programming support for LabVIEW, LabWindows/CVI, Visual Basic, and Visual C++. With the simulation mode now available in the NI-FGEN software, test and design engineers have the freedom to develop and prototype applications without the NI PXI-5404 hardware in their system.

Once again National Instruments (NI) comes up with a PXI plug-in sporting a smashing price vs. performance ratio. But, because I'm a believer that one should eat dessert last, I'll defer stating the price until I make my concluding remarks. Up-front stuff first. For those not up to speed on the PXI spec itself, it defines CompactPCI-based PC platforms and modules. The PXI bus definition includes environmental specs, standardized software, and timing and triggering features. Adherence to the spec conveys the benefit of standardization for environmentally hardened test-and-measurement, data acquisition, and industrial and factory-floor gear. Since its introduction, and promotion in no small way by NI, PXI is now considered an industry-standard architecture. Lots of folks enjoy its 132 Mbytes/s data rate and plug-and-play usability. Also, as with CompactPCI, PXI offers nearly twice as many peripheral slots as desktop PCI systems per bus segment. Multiple-segment PXI systems also offer more slots than extended desktop systems. Multi-Board Triggering For those of you working with ATE and test suites of multiple instruments, PXI also brings trigger-bus and reference clocking to the table. This is a feature that enhances multi-board synchronization. The spec defines a so-called Star Trigger Bus for precise system timing. The PXI spec also includes local bus definitions for sideband communication between adjacent peripherals. On the software side, PXI also defines system-level software for Microsoft Windows products. And, according to the spec, PXI peripherals must include appropriate device drivers. Extraordinary Specs Tell the Story Back to NI's single-slot Model PXI-5404 frequency source. With its very tight level-accuracy, 300 Msamples/s D/A converter sample rate, and a range extending from 9,000 Hz up to 105 MHz, the PXI-5404 really is the essence of a state-of-the-art instrument. Just look at its inherent phase range for proof. It extends from 0 degrees to 359.978 degrees, with a resolution of more than 16,000 steps. That gives you a resolution of 0.022 degrees, which is remarkable. In use, the system is designed to feed 50 W loads through a gold-plated SMB connector, where it will deliver up to 2 V (peak-to-peak) signals. Like its phase resolution, the PXI-5404 achieves high amplitude resolution, too (the loaded amplitude resolution is 2,048 steps), of roughly 489 µV/step. Likewise, the PXI-5404's clock output, also available at an SMB port, touts rise and fall times on the order of 4 ns. As the company's press statement notes (but it's worth reiterating), the frequency resolution is 1.07 µHz. With those kinds of specs, the designers of the PXI-5404 surely considered noise and distortion too. For its sine output, the card touts an average noise density spec of just 0.126 µV (rms) per root-hertz. The total harmonic distortion (THD) is -56 dB at 1 MHz, and -36 dB at 100 MHz. DDS Silicon Magic This type of performance accrues to the use of an on-board direct digital synthesizer (DDS), which works in conjunction with a phase-locked loop (PLL). If you look closely at the circuit board, you'll notice an Analog Devices Inc. (ADI) Type AD9852 PLL chip lurking quietly. ADI's AD9852 is an all-CMOS 300 MHz DDS that packs its own 12-bit D/A converters and phase comparator. When referenced to an accurate clock source, this screamer of a chip generates extremely stable frequency-, phase-, and amplitude-programmable sine-wave outputs. In the NI board, the AD9852's on-chip DDS and PLL combine to let you program and set amplitude, frequency, and phase of both the board's sine and clock outputs, as well as the duty cycle of the clock output. This silicon is an example of state-of-the-art mixed-signal chip-level integration, and the NI board is a masterful design embedding such an IC on a single-board product. NI's FGEN software mentioned briefly in its press statement is also worth underscoring. With FGEN, included with all of NI's waveform and function generators, you can seamlessly integrate the function set of this hardware into NI's LabVIEW, or Measurement Studio, or using C, C++, or VisualBASIC languages. FGEN includes NI's so-called Source Soft Front Panel that lets you operate the PXI-5404, without programming, through screens such as this one. click for full-size image Now comes the good part: dessert. You can purchase this product for less than $1500. Not bad, eh? For more details, contact National Instruments Corp. 11500 North Mopac Expwy. Austin, TX 78759-3504 Phone: (512) 683-0100 FAX: 512-683-8411 Web: www.ni.com

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