鈭?/div>
Hz, Differential
Programming Optimizes Noise Figure
鈥?24dB to 45dB Gain
鈥?40MHz Bandwidth
鈥?Differential Input /Output
q
LOW CROSSTALK: 52dB at Max Gain, 5MHz
q
HIGH-SPEED VARIABLE GAIN ADJUST
q
SWITCHABLE EXTERNAL PROCESSING
DESCRIPTION
The VCA2612 is a highly integrated, dual receive channel,
signal processing subsystem. Each channel of the product
consists of a low noise preamplifier (LNP) and a Variable Gain
Amplifier (VGA). The LNP circuit provides the necessary
connections to implement Active Termination (AT), a method
of cable termination which results in up to 4.6dB noise figure
improvement. Different cable termination characteristics can
be accommodated by utilizing the VCA2612鈥檚 switchable
LNA feedback pins. The LNP has the ability to accept both
differential and single-ended inputs, and generates a differen-
tial output signal. The LNP provides strappable gains of 5dB,
17dB, 22dB, and 25dB.
The output of the LNP can be accessed externally for further
signal processing, or fed directly into the VGA. The VCA2612鈥檚
VGA section consists of two parts: the Voltage Controlled
Attenuator (VCA) and the Programmable Gain Amplifier
(PGA). The gain and gain range of the PGA can be digitally
programmed. The combination of these two programmable
elements results in a variable gain ranging from 0dB up to a
maximum gain as defined by the user through external connec-
tions. The output of the VGA can be used in either a single-
ended or differential mode to drive high-performance
Analog-to-Digital (A/D) converters.
The VCA2612 also features low crosstalk and outstanding
distortion performance. The combination of low noise, and gain
range programmability make the VCA2612 a versatile building
block in a number of applications where noise performance is
critical. The VCA2612 is available in a TQFP-48 package.
Maximum Gain Select
FBSW
CNTL
RF
2
RF
1
LNP
OUT
N
VCA
IN
N
VCA
CNTL
MGS
1
MGS
2
MGS
3
SWFB
FB
VCA2612
(1 of 2 Channels)
APPLICATIONS
q
ULTRASOUND SYSTEMS
q
WIRELESS RECEIVERS
q
TEST EQUIPMENT
Analog
Control
Maximum Gain
Select
C
F
Input
C
C
LNP
IN
P
LNP
GS1
LNP
GS2
LNP
GS3
LNP
IN
N
VCA
OUT
P
Programmable
Gain Amplifier
24 to 45dB
VCA
OUT
N
Low Noise
Preamp
5dB to 25dB
Voltage
Controlled
Attenuator
LNP
Gain Set
LNP
OUT
P
VCA
IN
P
SEL
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.
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.
Copyright 漏 2000, Texas Instruments Incorporated
www.ti.com