AD9272_09 datasheet(21/44 Pages) AD

21 / 44 page

AD9272

Rev. C | Page 21 of 44

THEORY OF OPERATION

ULTRASOUND

The primary application for the AD9272 is medical ultrasound.

Figure 36 shows a simplified block diagram of an ultrasound

system. A critical function of an ultrasound system is the time

gain control (TGC) compensation for physiological signal

attenuation. Because the attenuation of ultrasound signals is

exponential with respect to distance (time), a linear-in-dB VGA

is the optimal solution.

Key requirements in an ultrasound signal chain are very low

noise, active input termination, fast overload recovery, low

power, and differential drive to an ADC. Because ultrasound

machines use beam-forming techniques requiring large binary-

weighted numbers (for example, 32 to 512) of channels, using

the lowest power at the lowest possible noise is of chief importance.

Most modern machines use digital beam forming. In this

technique, the signal is converted to digital format immediately

following the TGC amplifier, and then beam forming is

accomplished digitally.

The ADC resolution of 12 bits with up to 80 MSPS sampling

satisfies the requirements of both general-purpose and high-

end systems.

Power conservation and low cost are two of the most important

factors in low-end and portable ultrasound machines, and the

AD9272 is designed to meet these criteria.

For additional information regarding ultrasound systems, refer

to “How Ultrasound System Considerations Influence Front-End

Component Choice,” Analog Dialogue, Volume 36, Number 1,

May–July 2002, and “The AD9271—A Revolutionary Solution

for Portable Ultrasound,” Analog Dialogue, Volume 41, Number 3,

July 2007.

BEAM-FORMER

CENTRAL CONTROL

Rx BEAM FORMER

(B AND F MODES)

COLOR

DOPPLER (PW)

PROCESSING

(F MODE)

IMAGE AND

MOTION

PROCESSING

(B MODE)

SPECTRAL

DOPPLER

PROCESSING

MODE

DISPLAY

AUDIO

OUTPUT

Tx BEAM FORMER

CW (ANALOG)

BEAM FORMER

TRANSDUCER

ARRAY

128, 256, ...

ELEMENTS

BIDIRECTIONAL

CABLE

MUX/

DEMUX

T/R

SWITCHES

Tx HV AMPs

MULTICHANNELS

AD9272

AAF

VGA

LNA

ADC

Figure 36. Simplified Ultrasound System Block Diagram

AD9272 Datasheet(PDF) 21 Page - Analog Devices

AD9272 Datasheet(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL