VCA8500_0803 Datasheet, PDF (1/40 Pages) Texas Instruments – 8-Channel, Ultralow-Power, Variable Gain Amplifier with Low-Noise Pre-Amp

VCA8500
www.ti.com
SBOS390A – JANUARY 2008 – REVISED MARCH 2008
8-Channel, Ultralow-Power, Variable Gain Amplifier
with Low-Noise Pre-Amp
FEATURES
1
•2345 Ultralow Power: 65mW/Channel
• Low Noise: 0.8nV/√Hz
• Low-Noise Pre-Amp (LNP):
– 20dB Fixed Gain
– 250mV_PP Linear Input Range
• Variable Gain Amplifier:
– Gain Control Range: 46dB
– Selectable PGA Gain:
20dB, 25dB, 27dB, 30dB
– Fast Overload Recovery
– Output Clamping Control
• Integrated Low-Pass Filter:
– Second-Order, Linear Phase
– Bandwidth: 10MHz, 15MHz
• High Accuracy:
– Low Gain Error: ±0.5dB
– Excellent Channel Matching: ±0.25dB
• Distortion, HD2: –50dBc at 5MHz
• Integrated CW Switch Matrix:
– Easy Current Summing
• Serial Control Interface
• Small Package: QFN-64, 9×9mm
APPLICATIONS
• Medical Imaging, Ultrasound Systems
– Portable Systems
– Low- and Mid-Range Systems
DESCRIPTION
The VCA8500 is an 8-channel variable gain amplifier
consisting of a low-noise pre-amplifier (LNP) and a
variable-gain amplifier (VGA). This combination,
along with the device features, makes it ideal for a
variety of ultrasound systems.
The LNP gain is fixed at 20dB, and has excellent
noise and signal handling characteristics. The gain of
the voltage-controlled attenuator can vary over a
46dB range with a 0V to 1.2V control voltage
common to all channels of the VCA8500.
The post-gain amplifier (PGA) can be programmed
for four gain settings: 20dB, 25dB, 27dB, or 30dB
gain. As a means to improve system overload
recovery time, the VCA8500 provides an internal
clamping function. The PGA settings as well the
clamp levels are controlled through the serial
interface.
The VCA8500 is built on TI’s BiCOM process and is
available in a small QFN-64 PowerPAD™ package.
SDI
Logic
CW Switch Matrix
(8 in ´ 10 out)
CW
OUT
LNA
IN
LNA
20dB
Attenuation
(46dB)
VCA8500
(1 of 8 Channels)
Gain
Control
NOTE (1): 20dB, 25dB, 27dB, or 30dB gain setting.
(1)
PGA
Clamping
Circuit
LPF
(Two-
pole)
OUT
OUT
1
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.
PowerPAD is a trademark of Texas Instruments.
2
Infineon is a registered trademark of Infineon Technologies.
3
SPI is a trademark of Motorola.
4
All other trademarks are the property of their respective owners.
5
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008, Texas Instruments Incorporated