The lowest B-mode power consumption of the analog front-end circuit is 1 100 MW per channel. In addition, the digital variable gain amplifier can ensure that the gains between channels can be aligned with each other, thus making it easier to select the signal spectrum. Wu Weiqiang told reporters that in the past, analog front-end circuits used analog variable gain transformers. Its disadvantages are that the analog control signal will have AC ripple, the gain between channels is difficult to align, and it is necessary to add digital-to-analog converter (DAC), operational amplifier and filter. The digital variable gain amplifier adopts the control mode without ripple, and the gain difference of different channels is less than 0.06dB (typical value), which is four times higher than that of the nearest competitor, so the quality of scanned images can be guaranteed to be clearer. In addition, the digital variable gain amplifier does not need to add any components, so it is easier to control through FPGA.
Low-power continuous-time sigma-delta analog-to-digital converter (ADC) is equipped with brick-wall anti-aliasing filter, which does not need external filter or oversampling. The built-in jitter filtering function can suppress the carrier phase noise. The dynamic range of CW Doppler system is 16 1dB/Hz, which can ensure accurate measurement. LM965 1 1 analog front-end circuit is only packaged in 187mm2, which is 27% smaller than other similar competitive products.
Transmit/receive system switch
LM96530 PowerWise ultrasonic transmitting/receiving system switch, 8 transmitting/receiving system switches, equipped with clamping diodes, can independently close a single channel. The input reference noise of this chip is only 0.5nV/√Hz, which is 55% higher than that of other switching circuits of transmitting/receiving systems, while the on-resistance is only16 Ω, which is 53% lower than that of other competitive products. Therefore, LM96530 switching circuit can improve the receiving sensitivity and image resolution of the system. The package of this chip is four times smaller than the vertical solution, which helps to reduce the size of the circuit board. The control function is implemented through daisy-chain SPI interface, which can reduce the number of FPGA input/output (I/O) pins required for setting parameters.
Transmitting system pulse generator
The pulse generator of LM96550 high-power ultrasonic transmission system has eight pulse generators with dampers, which can generate 50V bipolar pulses with peak current up to 2A and pulse frequency up to 20MHz. LM96550 chip can continuously monitor the temperature of the chip, and output a turn-off logic signal when necessary to provide overheating protection for the system.
Beamformer with configurable ultrasonic transmission system
LM96570 PowerWise can be equipped with a beamformer for ultrasonic transmission system. The built-in beamformer only produces small signal jitter, and its peak-to-peak jitter is 25ps lower than that of the beamformer used in FPGA chips, so it can greatly improve the resolution of scanned images in B mode and ensure that slow blood flow velocity can be measured when CW Doppler mode is adopted. LM96570 chip can simplify the circuit layout of the circuit board, so that the system designer can put this chip directly next to the pulse generator. In contrast, if the input/output pins (I/O) of an FPGA are connected to a pulse generator, the problem of common path selection must be solved. At the same time, American National Semiconductor Company provides various easy-to-use evaluation kits, reference circuit diagrams and design tools, so that customers can quickly and accurately test the system design and ensure that products can be brought to market faster.