AD9276 Analog Devices, AD9276 Datasheet - Page 21

• Manufacturer Part Number: AD9276
• Description: Octal LNA/VGA/AAF/12-Bit ADC and CW I/Q Demodulator
• Manufacturer: Analog Devices

Specifications of AD9276

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 80MSPS
• Interface: LVDS,Ser
• Analog Input Type: SE-Uni
• Ain Range: 2 V p-p
• Adc Architecture: n/a
• Pkg Type: QFP

THEORY OF OPERATION
ULTRASOUND
The primary application for the AD9276 is medical ultrasound.
Figure 45 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 beamforming techniques requiring large binary-weighted
numbers of channels (for example, 32 to 512), using the lowest
power at the lowest possible noise is of chief importance.
TRANSDUCER
128, 256, ETC.,
ELEMENTS
ARRAY
BIDIRECTIONAL
CABLE
DEMUX
MUX/
HV
Tx HV AMPLIFIERS
SWITCHES
Figure 45. Simplified Ultrasound System Block Diagram
T/R
Rev. 0 | Page 21 of 48
LNA
BEAMFORMER
CW (ANALOG)
Tx BEAMFORMER
OUTPUT
AUDIO
VGA
Most modern ultrasound machines use digital beamforming.
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
AD9276 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 3,
May–July 2002, and “The AD9271—A Revolutionary Solution for
Portable Ultrasound, ” Analog Dialogue, Volume 41, Number 7,
July 2007.
AAF
PROCESSING
SPECTRAL
DOPPLER
ADC
MODE
CENTRAL CONTROL
PROCESSING
MULTICHANNELS
IMAGE AND
(B MODE)
BEAMFORMER
Rx BEAMFORMER
(B AND F MODES)
MOTION
DISPLAY
DOPPLER (PW)
PROCESSING
(F MODE)
COLOR
AD9276