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National Semiconductor’s New Amplifier Family Eliminates EMI-Induced Errors in Analog Systems

PowerWise Op Amps with Integrated EMI Filters Enable Systems to Maintain Optimal Accuracy

Aug 25, 2008

August 25, 2008 – National Semiconductor Corp. (NYSE:NSM) today introduced three new operational amplifiers (op amps) with integrated electromagnetic interference (EMI) filters that maintain the accuracy of analog systems by reducing the effects of radio frequency (RF) interference. The LMV83x op amps deliver the industry’s highest EMI rejection ratio (EMIRR) of 120 dB, thereby eliminating EMI-induced errors. They also feature 3 MHz unity gain bandwidth while operating on only 240 uA of supply current. This yields a power-to-performance ratio of 80 uA per MHz, which places these devices among National’s PowerWise® family of energy-efficient products.

The LMV831 single, LMV832 dual and LMV834 quad EMI-hardened op amps reduce development time and board size by minimizing the need for metal shielding, filters and extra components. They are well-suited for use in phone accessories, medical instruments, precision weigh scales and other industrial electronic equipment that are sensitive to electromagnetic disturbances in noisy environments. For example, an injected RF signal in a weigh scale can result in as much as 1V of output offset, which would diminish a 10-bit analog-to-digital converter’s (ADC’s) resolution (1024 codes) to the equivalent of only 3-bits. Using an LMV83x op amp would only reduce resolution by 0.2-bits. A wide range of applications can benefit from EMI protection, including filters/buffers, photodiode preamp and piezoelectric sensors.

National’s LMV83x devices join the previously released LMV851/52/54 with 8 MHz unity gain bandwidth and LMV861/62 with 30 MHz of unity gain bandwidth. They are built on National’s proprietary CMOS7 process technology, which enables optimal performance while maximizing power-efficiency.

To assist engineers with determining an op amp’s EMI robustness, National developed the EMIRR specification (app note: AN-1698 www.national.com/an/AN/AN-1698.pdf), which quantifies how well various pins of the op amp reject RF interference. Evaluation boards are also available to accelerate the design process. Additionally, National provides signal path solutions by offering the LMV83x devices and 10-bit and 12-bit ADCs with 1 LSB performance and either a serial peripheral interface (SPI) or I2C interface. These ADCs include the ADC121SXX1, ADC101Sxx1, ADC122SXX1, ADC102Sxx1, ADC124SXX1, ADC104Sxx1, ADC128SXX2 and ADC108Sxx2 with SPI, and the ADC121C021 and ADC101C021 with I2C interface.

Technical Features of LMV831/32/34 EMI-Hardened Op Amps
The LMV831 single, LMV832 dual and LMV834 quad op amps feature CMOS inputs, a maximum input offset voltage of 1 mV, a rail-to-rail output stage and an input common-mode voltage range that includes ground. These devices provide a common-mode rejection ratio (CMRR) and a power supply rejection ratio (PSRR) of 93 dB. The LMV83x devices maintain stability for capacitive loads as large as 200 pF and offer a wide temperature range of -40 degrees C to 125 degrees C. The LMV831 is offered in a 5-pin SC70 package, while the LMV832 is offered in an 8-pin MSOP package and the LMV834 is offered in a 14-pin TSSOP package.

About National’s Amplifier Portfolio
Specializing in high-performance amplifiers and comparators, National Semiconductor offers a complete portfolio of op amps addressing the high-speed, precision, low-voltage and low-power markets with products ranging from building-block ICs to application-specific standard products (ASSPs). The company has a long history of setting industry standards in amplifiers and continues this trend with product releases on National’s advanced VIP10 bipolar and VIP50 BiCMOS processes. National also leads the industry in packaging technology with its revolutionary Silicon Dust™ and micro SMD packaging technologies. For more information on National’s amplifier products, visit www.national.com/amplifiers

Pricing and Availability
The LMV831 is priced at 55 cents each, the LMV832 is 79 cents each, and the LMV834 is priced at $1.10 each in 1,000-unit quantities. Samples of all three EMI-hardened op amps are available now and production quantities will be available in third quarter 2008.

For more information or to order samples and an evaluation board, visit www.national.com/pf/LM/LMV831.html, www.national.com/pf/LM/LMV832.html, and www.national.com/pf/LM/LMV834.html. National’s WEBENCH® Amplifiers Designer online tool supports a large selection of amplifiers. To explore these solutions, visit www.national.com/webench. To learn more about designing with amplifiers, visit our library at www.national.com/onlineseminar/#amps.

Note to Editors: To view a high-resolution downloadable photo of these products, visit National's photo gallery

About National’s PowerWise Brand
National’s PowerWise brand reflects the company’s energy-efficient product portfolio.  It signifies products with outstanding performance-to-power at the component level, as well as products that provide an outstanding, energy-efficient solution when coupled with other National parts. National’s PowerWise family of products features energy-efficient power management, operational amplifiers, interface, and data conversion products.  For more information about National’s PowerWise brand, visit: www.national.com/powerwise.

About National Semiconductor
National Semiconductor creates energy-efficient analog and mixed-signal semiconductors. Its PowerWise® products enable systems that consume less power, extend battery life, and generate less heat. Headquartered in Santa Clara, Calif., National reported sales of $1.89 billion for fiscal 2008 which ended May 25, 2008. Additional company and product information is available at www.national.com.