Eight-Channel Transmit/Receive Chipset for Portable Ultrasound Systems

Mon, 12/06/2010 - 3:31pm


National Semiconductor Corporation has unveiled an eight-channel ultrasound transmit/receive chipset specifically designed for portable ultrasound systems used in hospitals, clinics, ambulances and remote point-of-care facilities. The PowerWise® chipset’s innovative circuit architecture enables the design of both hand-carried and handheld units that deliver longer battery life and imaging performance comparable to larger console systems. National provides a complete eight-channel transmit/receive chipset, including receive analog front end (AFE), transmit/receive switch, transmit pulser and configurable transmit beamformer. This high-level of integration allows system designers to build lightweight 128-channel portable ultrasound systems with enhanced image quality and diagnostics in a small footprint. National supports the chipset with comprehensive evaluation kits, reference schematics and tools that help customers make detailed chip performance evaluations and accelerate time-to-market. “Previously, this level of ultrasound imaging quality was only attainable with large cart-based consoles,” said Dr. Norbert Gaus, chief executive officer of the Clinical Products Division of Siemens Healthcare. “National Semiconductor has significantly raised the bar in terms of imaging performance and low-power consumption for portable ultrasound systems.” The chipset includes four integrated circuits (ICs) that work together to deliver unmatched performance and power efficiency. For example, the transmit beamformer can be configured to calibrate the board trace delay mismatch and pulser delay mismatch. This significantly improves the distortion performance and enables second harmonic imaging. The transmit/receive switch gives system designers the flexibility to trade-off power versus performance by selecting different bias current settings. The company’s unique AFE architecture provides superior imaging quality and B-mode power consumption that is 10 percent lower than the closest comparable AFE. It includes the industry’s highest resolution digital variable gain amplifier (DVGA) and a low-power continuous-time sigma-delta (CTSD) analog-to-digital converter (ADC). The DVGA offers several advantages over traditional analog VGAs such as better channel-to-channel matching and higher spectral performance. The CTSD ADC provides inherent brickwall anti-aliasing filtering in comparison to higher power consuming, low-order anti-aliasing filters found in other AFEs that use conventional pipeline ADCs.
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The LM96511 AFE integrates eight channels of LNA, DVGA, 12-bit, 40-50 MHz ADC with LVDS data outputs and eight demodulators for CW Doppler beamforming. The AFE provides the lowest B-mode power consumption at 110 mW per channel. It enhances image quality with channel-to-channel gain matching of +/- 0.06 dB (typical) that is four times better than the closest comparable AFE. The integrated CW Doppler delivers 161 dB per Hz of dynamic range, enabling measurement of low velocity blood flow in organs such as the liver. The AFE delivers this performance in a 187 mm² package that’s 27 percent smaller than any other comparable AFE. The LM96530 PowerWise Ultrasound Transmit/Receive Switch contains eight transmit/receive switches with integrated clamping diodes and offers an individual channel shut-off capability. Compared to other T/R switches, the LM96530 provides 55 percent better input referred noise (0.5 nV/sqrt Hz) and 53 percent lower on-resistance (16 Ohms), thereby increasing receiver sensitivity and image resolution. The LM96530 reduces board space by 4x compared to discrete solutions, and its daisy-chained SPI control reduces the number of FPGA I/O pins required for programming. The LM96550 PowerWise Ultrasound Transmit Pulser contains eight pulsers with damper circuit that generates +/- 50V bipolar pulses with peak currents up to 2A and pulse rates up to 20 MHz. The LM96550 features over-temperature protection by continuously monitoring on-chip temperature and providing power-down logic output. The LM96570 PowerWise Ultrasound Configurable Transmit Beamformer provides an order of magnitude jitter performance improvement (25 ps pk-pk) over beamforming traditionally done in FPGAs. This enables much higher resolution imaging in B-mode and low blood velocity measurements in CW Doppler mode. The LM96570 simplifies board layout since system designers can place it directly next to the pulser, thereby avoiding the typical routing challenges of connecting an FPGA’s I/O pins to the pulser. Easy-to-use evaluation kits, reference schematics and tools from National allow for fast and accurate evaluation to help customers accelerate their time-to-market. National offers a full development package that includes the WaveVision 5 acquisition analysis hardware and software with user-friendly GUI for device programming and control.

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