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Semiconductors for Ultrasound Slide 9

There are other opportunities in the transmit and receive paths available today for designers to reduce power and size in the system. The transmit/receive switch, commonly known as the T/R switch, function prevents the high voltage pulses from damaging the receiver electronics. As shown in the diagram on this slide, it is made up of a protection diode bridge and clamp diodes. This block has been traditionally done discretely, but today there is a fully integrated T/R switch available. The tradeoffs for T/R switch integration include insertion loss, capacitance, and cross-talk, which are most visible in high-end systems and are adequate for most portable applications. An integrated T/R switch solution offers over 70% board space savings; the pros outweigh the cons for the portable system design. Another benefit is the power savings. The T/R switch usually remains on to protect the receiver path from the high voltage pulses, bias currents are constantly being drawn which affects the power consumption. Programmable bias currents are an option to adjust this power consumption. The TX810 illustrated here contains a 3-bit interface used to program a 7 mA range of bias currents. With this solution, an ultrasound system designer can program seven different current settings and also have a power down mode to further reduce power consumption.

PTM Published on: 2013-04-30