AD8372_15 Datasheet, PDF (1/16 Pages) Analog Devices – 41 dB Range, 1 dB Step Size, Programmable Dual VGA

FEATURES
Dual independent digitally controlled VGA
Differential input and output
150 Ω differential input
Open-collector differential output
7.8 dB noise figure to 100 MHz @ maximum gain
HD2/HD3 better than 77 dBc for 1 V p-p differential output
−3 dB bandwidth of 130 MHz
41 dB gain range
1 dB step size ± 0.2 dB
Serial 8-bit bidirectional SPI control interface
Wide input dynamic range
Pin-programmable output stage
Power-down feature
Single 5 V supply: 106 mA per channel
32-lead LFCSP, 5 mm × 5 mm package
APPLICATIONS
Differential ADC drivers
CMTS upstream direct sampling receivers
CATV modem signal scaling
Generic RF/IF gain stages
Single-ended-to-differential conversion
GENERAL DESCRIPTION
The AD8372 is a dual, digitally controlled, variable gain
amplifier (VGA) that provides precise gain control, high IP3,
and low noise figure. The excellent distortion performance and
moderate signal bandwidth make the AD8372 a suitable
gain control device for a variety of multichannel receiver
applications.
For wide input dynamic range applications, the AD8372
provides a broad 41 dB gain range. The gain is programmed
through a bidirectional 4-pin serial interface. The serial inter-
face consists of a clock, latch, data input, and data output lines
for each channel.
The AD8372 provides the ability to set the transconductance of
the output stage using a single external resistor. The RXT1 and
RXT2 pins provide a band gap derived stable reference voltage
of 1.56 V. Typically 2.0 kΩ shunt resistors to ground are used to
set the maximum gain to a nominal value of 31 dB. The current
41 dB Range, 1 dB Step Size,
Programmable Dual VGA
AD8372
FUNCTIONAL BLOCK DIAGRAM
ENB1
IPC1
INC1
RXT1
AD8372
CHANNEL 1 POSTAMP
REF1
OPC1
ONC1
CLK1
SDO1
SDI1
LCH1
RXT2
IPC2
INC2
ENB2
REGISTERS
AND
GAIN DECODER
CHANNEL 2 POSTAMP
Figure 1.
CLK2
SDO2
SDI2
LCH2
OPC2
ONC2
REF2
setting resistors can be adjusted to manipulate the gain and
distortion performance of each channel. This is a flexible
feature in applications where it is desirable to trade off distortion
performance for lower power consumption.
The AD8372 is powered on by applying the appropriate logic
level to the ENB1, ENB2 pins. When powered down, the AD8372
consumes less than 2.6 mA and offers excellent input-to-output
isolation. The gain setting is preserved when powered down.
Fabricated on an Analog Devices, Inc., high frequency BiCMOS
process, the AD8372 provides precise gain adjustment capabilities
with good distortion performance. The quiescent current of the
AD8372 is typically 106 mA per channel. The AD8372 amplifier
comes in a compact, thermally enhanced 5 mm × 5 mm 32-lead
LFCSP package and operates over the temperature range of
−40°C to +85°C.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]
www.analog.com
Fax: [phone] ©2007–2011 Analog Devices, Inc. All rights reserved.