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National Semiconductor Introduces Industry’s First Differential Wideband Amplifier with Programmable Output Limiting Clamp

PowerWise Amplifier Provides Over-Voltage Protection When Driving High-Speed A/D Converters for Automotive Safety Applications

National Semiconductor Corp. October 22, 2008 introduced the industry’s first wideband 900 MHz fully differential amplifier to include a programmable output limiting clamp for protecting analog-to-digital converters (ADC) and other downstream circuitry from over-voltage events. The amplifier’s integrated clamp provides improved distortion, higher bandwidth and clamping accuracy compared with existing amplifiers that must use external discrete clamping circuits to provide the same protection.

The LMH6553 operates over the -40 degrees C to 125 degrees C temperature range and is well-suited for processing wide dynamic-range signals in automotive safety applications, including collision avoidance, lane departure and back-up warning systems. A member of National’s PowerWise® family of energy-efficient products, the LMH6553 features 900 MHz unity-gain bandwidth while operating on only 29 mA of supply current. This results in an industry-leading power-to-performance ratio of 32 uA per MHz.

Additionally, National provides designers with a variety of signal path solutions by pairing the LMH6553 with one of more than 40 differential input 8-bit to 14-bit ADCs featuring sampling rates up to 1 giga samples per second (GSPS). These ADCs include the ADC08D1000, ADC10080, ADC12C170 and ADC14DS105.

Key Features – LMH6553 Amplifier with Output Limiting Clamp
The LMH6553 operates across a wide supply range from single 4.5V up to a split +/- 6V supply. The LMH6553 provides 4 kV of electrostatic discharge (ESD) protection and its adjustable output clamp has a single reference control that sets the internal high and low clamp levels versus the multiple reference control levels required with external discrete clamps. Additionally, the LMH6553 features a 600 picosecond (ps) clamp overdrive recovery time and guaranteed +/- 53 mV clamp accuracy, allowing clamp levels to be accurately set relative to the desired signal.

The LMH6553’s -0.1 mV/degree C clamp-accuracy temperature coefficient provides excellent clamp level stability and enables signals to swing to within 22 mV of the clamp level before distortion degrades by 3 dB. The device’s current feedback architecture coupled with low input voltage noise of 1.2 nV/sqrt Hz and low input current noise of 13.6 pA/sqrt Hz delivers lower output noise at higher gain settings than other competitive differential amplifiers. The LMH6553’s external gain set resistors and the output common-mode control allow it to be configured for a variety of gains in AC- and DC-coupled ADC driving applications.

From: http://www.national.com



Publication date: 28.10.2008


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