VCA2615PFBR Datasheet, PDF (1/33 Pages) Texas Instruments – Dual, Low-Noise

VCA2615
SBOS316D − JULY 2005 − REVISED OCTOBER 2008
Dual, Low-Noise
Variable-Gain Amplifier with Preamp
FEATURES
D VERY LOW NOISE: 0.7nV//Hz
D LOW-NOISE PREAMP (LNP)
− Active Termination
− Programmable Gains: 3, 12, 18, 22dB
− Programmable Input Impedance (R_F)
− Buffered, Differential Outputs for CW
Processing
− Excellent Input Signal Handling
Capabilities
D LOW-NOISE VARIABLE-GAIN AMPLIFIER
− High/Low-Mode (0/+6dB)
− 52dB Gain Control Range
− Linear Control Response: 22dB/V
− Switchable Differential Inputs
− Adjustable Output Clipping-Level
D BANDWIDTH: 42MHz
D HARMONIC DISTORTION: −55dB
D 5V SINGLE SUPPLY
D LOW-POWER: 154mW/Channel
D POWER-DOWN MODES
APPLICATIONS
D MEDICAL AND INDUSTRIAL ULTRASOUND
SYSTEMS
− Suitable for 10-Bit and 12-Bit Systems
D TEST EQUIPMENT
DESCRIPTION
The VCA2615 is a dual-channel, variable gain amplifier
consisting of a Low-Noise Preamplifier (LNP) and a Variable-
Gain Amplifier (VGA). This combination along with the device
features makes it well-suited for a variety of ultrasound
systems.
The LNP offers a high level of flexibility to adapt to a wide range
of systems and probes. The LNP gain can be programmed to
one of four settings (3dB, 12dB, 18dB, 22dB), while
maintaining excellent noise and signal handling
characteristics. The input impedance of the LNP can be
controlled by selecting one of the built-in feedback resistors.
This active termination allows the user to closely match the
LNP to a given source impedance, resulting in optimized
overall system noise performance. The differential LNP
outputs are provided either as buffered outputs for further CW
processing, or fed directly into the variable-gain amplifier
(VGA). Alternatively, an external signal can be applied to the
differential VGA inputs through a programmable switch.
Following a linear-in-dB response, the gain of the VGA can be
varied over a 52dB range with a 0.2V to 2.5V control voltage
common to both channels of the VCA2615. In addition, the
overall gain can be switched between a 0dB and +6dB
postgain, allowing the user to optimize the output swing of
VCA2615 for a variety of high-speed Analog-to-Digital
Converters (ADCs). As a means to improve system overload
recovery time, the VCA2615 provides an internal clipping
function where an externally applied voltage sets the desired
clipping level.
The VCA2615 operates on a single +5V supply and is
available in a small QFN-48 (7x7mm) or TQFP package.
FB1 FB2 FB3 FB4 LNP_OUT− LNP_OUT+ VCA_IN+ VCA_IN−
Feedback
Resistors
+1
+1
H/L
(0dB or
+6dB)
LNP_IN+
LNP_IN−
LNP
(3, 12, 18, 22dB)
1/2 VCA2615
G1 G1
MUX
VGA
52dB
Range
VCA_INSEL
V_CNTL V_CLMP
VCA_OUT+
VCA_OUT−
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PRODUCTION DATA information is current as of publication date. Products
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