September 27, 2010
The PowerWise chipset balances low power with high-quality imaging for portable ultrasound applications.
Portable ultrasound systems are paving the way for better healthcare in rural and developing areas, on the battlefield, and in traditional clinical environments. But as systems shrink in size, OEMs have grappled with how to achieve low power consumption and high image quality in such a small package size. Addressing this need, National Semiconductor Corp. has introduced what it claims is the first eight-channel transmit/receive chipset for portable ultrasound systems.
Consisting of a receive analog front end (AFE), a transmit/receive switch, a transmit pulser, and a transmit beamformer, the PowerWise chipset combines an optimized design with advanced integrated circuit fabrication and packaging, according to Suresh Ram, director of National Semiconductor's medical key market segment group. "It's always a tradeoff of power versus performance, and what we're working on in this solution is a balance between performance and power," he adds.
Helping to strike this balance is the PowerWise AFE, which the company boasts has a 10% lower B-mode power consumption than competing AFEs. It also features a low-power continuous-time sigma-delta (CTSD) analog-to-digital convertor, integrated continuous-wave Doppler, and a high-resolution digital variable-gain amplifier (DVGA) technology--all condensed into an 11 x 17-mm chip package. Furthermore, National Semiconductor maintains that its DVGA technology employs an architecture that supports FPGA control for system flexibility and improves channel-to-channel gain matching and spectral performance.
The CTSD convertor, on the other hand, offers the benefit of fast recovery from overload. "By passing the probe over the rib cage or bone, that can lead to an overload," Ram states. "On the image side, you'll see some saturation of the image; it's important how quickly the system recovers from saturation. With this [CTSD], because it's a very high oversampled architecture, the recovery is almost instantaneous in the event of a saturation--it's in the order of tens of nanoseconds."
In terms of transmission functionality, the transmit beamformer enables flexibility, low jitter, and high resolution, while the chipset's pulser supports high-performance imaging that the company says is comparable to that of a conventional ultrasound console. In addition, the transmit/receive switch, which integrates an active damping circuitry, offers low noise, high sensitivity, and high quality. "Each channel of the chip can be separately controlled; each chip is connected by a simple daisy-chain approach," Ram explains. "Using the SPI interface from the FPGA, you can control all of these chips, as opposed to traditional implementations where you need resources in the FPGA for each one of these chips. So, you reduce board size and ease of implementation gets better."
Although each component is offered as a stand-alone product, the PowerWise chipset is designed to serve as a high-performance end-to-end solution that can replace various proprietary in-house design methods. Consequently, the use of the analog subsystem solution can help to streamline operations, reduce the design cycle, and eliminate certain external components, thereby minimizing board space, according to Ram.
"We brought this [chipset] together utilizing a unique combination of process technology and package technology coupled with circuit architecture to provide a high-performance, low-power solution that drives high-quality imaging in portable systems with a longer battery life," he states.
National Semiconductor Corp.
Santa Clara, CA
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