8-Channel

VARIABLE GAIN AMPLIFIER

FEATURES

q 3V OPERATION

q LOW INPUT NOISE: 1.2nV

q EXTREMELY LOW POWER OPERATION:

75mW/CHANNEL

q INTEGRATED LOW-PASS, 2-POLE FILTER

14MHz BANDWIDTH

VCA8613

SBOS200C – APRIL 2003 – REVISED MARCH 2004

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Copyright © 2003-2004, Texas Instruments Incorporated

LNAIN1

LNA

V

LNA

V

LNA

Attenuator

Analog

Control

PGA

2-Pole

Filter

CW Processor

5x8

FIFO

LNAIN8

LNA

Attenuator

PGA

2-Pole

Filter

•

•

•

•

•

•

DATA

CLK

CS

Serial

Interface

DESCRIPTION

The VCA8613 is an 8-channel variable gain amplifier ideally

suited to portable ultrasound applications. Excellent dynamic

performance enables use in low-power, high-performance

portable applications. Each channel consists of a Low-Noise

pre-Amplifier (LNA) and a Variable Gain Amplifier (VGA). The

differential outputs of the LNA can be switched through the

8x10 cross-point switch, which is programmable through the

serial interface input port.

The output of the LNA is fed directly into the VGA stage. The

VGA consists of two parts, a Voltage Controlled Attenuator

(VCA) and a Programmable Gain Amplifier (PGA). The gain and

q INTEGRATED INPUT CLAMP DIODES

q DIFFERENTIAL OUTPUT

q INTEGRATED INPUT LNA

q READABLE CONTROL REGISTERS

q INTEGRATED CONTINUOUS WAVE (CW)

PROCESSOR

gain range of the PGA can be digitally configured separately. The

gain of the PGA can be varied between two discrete settings of

21dB and 26dB. The VCA has four programmable maximum

attenuation settings: 29dB, 33dB, 36.5dB, and 40dB. Also, the

VCA can be continuously varied by a control voltage from 0dB to

a maximum of 29dB, 33dB, 36.5dB, and 40dB.

The output of the PGA feeds directly into an integrated

2-pole, low-pass filter, allowing for direct connection to a

differential input Analog-to-Digital Converter (ADC), such as

the ADS5121 or ADS5122 from Texas Instruments. The

VCA8613 is available in a TQFP-64 package.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.