Octal Ultrasound AFE

With Digital Demodulator

Data Sheet

AD9670

Rev. Sp0

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FEATURES

8 channels of LNA, VGA, AAF, ADC, and digital demodulator/

decimator

Low power: 150 mW per channel, TGC mode, 40 MSPS;

65 mW per channel, CW mode; <30 mW at power-up

10 mm × 10 mm, 144-ball CSP-BGA

TGC channel input-referred noise: 0.8 nV/

√Hz, maximum gain

Flexible power-down modes

Fast recovery from low power standby mode: <2 μs

Low noise preamplifier (LNA)

Input-referred noise: 0.78 nV/√Hz, gain = 21.6 dB

Programmable gain: 15.6 dB/17.9 dB/21.6 dB

0.1 dB compression: 1.00 V p-p/.75 V p-p/.45 V p-p

Flexible active input impedance matching

Variable gain amplifier (VGA)

Attenuator range: 45 dB, linear-in-dB gain control

Postamp gain (PGA): 21 dB/24 dB/27 dB/30 dB

Antialiasing filter (AAF)

Programmable second-order LPF from 8 MHz to 18 MHz or

13.5 MHz to 30 MHz and HPF

Analog-to-digital converter (ADC)

SNR: 75 dB, 14 bits up to 125 MSPS

Configurable serial LVDS

CW mode harmonic rejection I/Q demodulator

Individual programmable phase rotation

Dynamic range per channel: >160 dBc/√Hz

Close-in SNR: 156 dBc/√Hz, 1 kHz offset, −3 dBFS

Digital demodulator/decimator

I/Q demodulator with programmable oscillator FIR

decimation filter: 16 taps per decimation factor

GENERAL DESCRIPTION

The AD9670 is designed for low cost, low power, small size, and

ease of use for medical ultrasound. It contains eight channels of a

variable gain amplifier (VGA) with a low noise preamplifier (LNA),

a CW harmonic rejection I/Q demodulator with programmable

phase rotation, an antialiasing filter (AAF), an analog-to-digital

converter (ADC), and a digital demodulator and decimator for

data processing and bandwidth reduction.

Each channel features a maximum gain of up to 52 dB, a fully

differential signal path, and an active input preamplifier termination.

The channel is optimized for high dynamic performance and

low power in applications where a small package size is critical.

The LNA has a single-ended-to-differential gain that is selectable

through the SPI. Assuming a 15 MHz noise bandwidth (NBW) and

a 21.6 dB LNA gain, the LNA input SNR is 94 dB. In CW Doppler

mode, each LNA output drives an I/Q demodulator that has inde-

pendently programmable phase rotation with 16 phase settings.

Power-down of individual channels is supported to increase battery

life for portable applications. Standby mode allows quick power-

up for power cycling. In CW Doppler operation, the VGA, AAF,

and ADC are powered down. The ADC contains several features

designed to maximize flexibility and minimize system cost, such as

a programmable clock, data alignment, and programmable digital

test pattern generation. The digital test patterns include built-in

fixed patterns, built-in pseudorandom patterns, and custom

user-defined test patterns entered via the serial port interface.

This product is protected by a U.S. patent.

FUNCTIONAL BLOCK DIAGRAM

AAF

VGA

LNA

CWD AND I/Q

DEMODULATOR

8 CHANNELS

SERIAL

PORT

INTERFACE

DATA

RATE

MULTIPLIER

REFERENCE

LO

GENERATION

LO-A TO LO-H

LOSW-A TO LOSW-H

LI-A TO LI-H

LG-A TO LG-H

DOUTA+ TO DOUTH+

DOUTA– TO DOUTH–

DVDD

DRVDD

NCO

CWQ+

CWQ–

CWI+

CWI–

STBY

PDWN

AVDD2

AVDD1

FCO–

FCO+

DCO+

DCO–

SERIALIZER

LVDS

DEMODULATOR/

DECIMATOR

14-BIT

ADC

AD9670

Figure 1.

For more information about the AD9670, contact Analog Devices, Inc., at highspeed.converters@analog.com.