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AD8327_15 Datasheet, PDF (1/20 Pages) Analog Devices – 5 V CATV Line Driver Coarse Step Output Power Control | |||
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a
5 V CATV Line Driver Coarse Step
Output Power Control
AD8327
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Supports DOCSIS Standard for Reverse Path
Transmission
VCC (5 PINS)
BYP
Gain Programmable in 6.02 dB Steps over a 48.16 dB
R1
Range
AD8327
Low Distortion at 60 dBmV Output
VIN+
â63 dBc SFDR at 21 MHz
â57 dBc SFDR at 42 MHz
Output Noise Level
â47 dBmV in 160 kHz
Maintains 75 â Output Impedance
Transmit Enable and Transmit Disable Modes
Upper Bandwidth: 160 MHz (Full Gain Range)
E 5 V Supply Operation
Supports SPI Interfaces
APPLICATIONS
T Gain-Programmable Line Driver
DOCSIS High-Speed Data Modems
Interactive Cable Set-Top Boxes
PC Plug-in Cable Modems
E General-Purpose Digitally Controlled Variable Gain Block
DIFF OR
SINGLE
INPUT
VINâ
AMP
VERNIER
R2
ZIN (SINGLE) = 800â
ZIN (DIFF) = 1.6kâ
ATTENUATION
CORE
POWER
AMP
VOUT
8
DECODE
ZOUT = 75â
8
DATA LATCH
POWER-DOWN
LOGIC
CXR
8
SHIFT
REGISTER
DATEN DATA CLK GND (5 PINS) TXEN SLEEP
L GENERAL DESCRIPTION
The AD8327 is a low-cost, digitally controlled, variable gain
amplifier optimized for coaxial line driving applications such as
cable modems that are designed to the MCNS-DOCSIS
upstream standard. An 8-bit serial word determines the desired
O output gain over a 48.16 dB range resulting in gain changes of
6.02 dB/major carry.
The AD8327 comprises a digitally controlled variable attenuator
of 0 dB to â48.16 dB, which is preceded by a low noise, fixed
S gain buffer and followed by a low distortion, high power amplifier.
The AD8327 accepts a differential or single-ended input
signal. The output is specified for driving a 75 ⦠load, such
as coaxial cable.
B Distortion performance of â63 dBc is achieved with an output
level up to 60 dBmV at 21 MHz bandwidth. A key performance
and cost advantage of the AD8327 results from the ability to
O maintain a constant 75 ⦠output impedance during Transmit
â50
VOUT = 60dBmV @ MAX GAIN
â55
HD3
â60
HD2
â65
â70
â75
5
15
25
35
45
55
65
FUNDAMENTAL FREQUENCY â MHz
Figure 1. Harmonic Distortion vs. Frequency
Enable and Transmit Disable conditions. In addition, this
device has a sleep mode function that reduces the quiescent
current to 5 mA.
The AD8327 is packaged in a low-cost 20-lead TSSOP, operates
from a single 5 V supply, and has an operational temperature
range of â40°C to +85°C.
REV. 0
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. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2001
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