Chipset Nat Semi for portable ultrasound scanners




Description

 

The LM96511 is an 8-channel integrated analog front end (AFE) module for multi-channel applications, particularly medical ultrasound. Each of the 8 signal paths consists of a low noise amplifier (LNA), a digitally programmable variable gain amplifier (DVGA) and a 12-bit, 40 Mega Samples Per Second (MSPS) analog-to-digital converter (ADC) with Instant Overload Recovery (IOR). The architecture of the DVGA is a digitally-controlled linear-in-dB step attenuator driving a fixed-gain post-amplifier (PA). The ADC uses a Continuous-Time-Sigma-Delta (CTΣΔ) architecture with digital decimation filtering to maximize dynamic performance and provide an alias free input bandwidth to ADC CLK / 2. The ADC digital outputs are serialized and provided on differential LVDS outputs. The ADC includes an on-chip clock cleaner PLL.

In addition, for baseband CW Doppler Beamformer applications, an 8-channel demodulator with 16 discrete phase rotation angles is included.

Selective power reduction is included to minimize consumption of idle sections during interleaved imaging modes.

An SPI™ compatible serial interface allows dynamic digital programming and control. Texas Instruments offers a full development package for sale which includes acquisition analysis hardware and software with user friendly GUI for device programming and control.

Features

  • 8-Channel LNA, DVGA, and 12-bit Continuous Time ΣΔ ADC
  • Programmable Active Termination LNA
  • 8-channel, Integrated CW Doppler Beamforer
  • Low-Power Consumption
  • Embedded ADC Digital Filter
  • ADC Instant Overload Recovery
  • Embedded ADC “Clock-Cleaning” PLL
  • 11 mm x 17 mm RoHS NFBGA Package

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Chipset Nat Semi  for portable ultrasound scanners




The Doppler block delivers 161dB/Hz of dynamic range, “enabling measurement of low velocity blood flow in organs such as the liver”, said National.

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The digital variable gain amplifier (VGA), which retains an analogue signal path, significantly cuts spurious modulation of the signal compared with an all-analogue VGA, claims Ram.

“It does not spread the signal so there is more resolution and you can get low-velocity tones that otherwise the FPGA would have to extract,” he said.

To cut anti-aliasing filter requirements, the firm is noise-shaping using high-order ?? ADCs.

Sampling at 40Msample/s, the continuous time brick wall design passes 20MHz, but rejects signals above 30MHz by at least 70dB.

B-mode scan power consumption is 110mW/channel, and channel-to-channel gain matching is typically +/-0.06dB.

The LM96530 T-R switch has eight transmit-receive channels with integrated clamping diodes and individual channel shut-off.

Input referred noise is 0.5nV/?Hz and on-resistance is 16?.

To reduce the number of FPGA pins needed to operates multiple switches, controls signals can be daisy-chained between chips.

Dissipation in the switch very much depends on the application, said Ram, adding: “Typical power consumption for this performance level is in the order of 1W.”

The LM96550 transmit pulser contains eight pulsers with damper circuit that generates +/-50V pulses with peak currents up to 2A and pulse rates up to 20MHz.

Over-temperature protection is included.

Jitter from the LM96570 transmit beam former is 25ps pk-pk, which Ram claims is around 10 times better than leaving the job to the FPGA, and allows the use of a smaller FPGA.

 

 

For more read: Chipset Nat Semi  for portable ultrasound scanners

 




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