Gain Programmable
CATV Line Driver
a
AD8321
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Linear in dB Gain Response Over >53 dB Range
Drives Low Distortion >11 dBm Signal into 75 � Load:
–53 dBc SFDR at 42 MHz
VCC
GND
Very Low Output Noise Level
Maintains Constant 75 � Output Impedance
Power-Up and Power-Down Condition
No Line Transformer Required
Upper Bandwidth: 235 MHz (Min Gain)
9 V Single Supply Operation
Power-Down Functionality
PWR
AMP
AD8321
VOUT
VIN+
VIN–
REVERSE
AMP
INV
ATTENUATOR CORE
DATA LATCH
Supports SPI Interface
Low Cost
POWER-
DOWN/
SWITCH
INTER
PD
DATA SHIFT REGISTER
SDATA
APPLICATIONS
Gain Programmable Line Driver
HFC High Speed Data Modems
Interactive CATV Set-Top Boxes
CATV Plant Test Equipment
General Purpose IF Variable Gain Block
DATEN CLK
DESCRIPTION
The AD8321 is packaged in a low cost 20-lead SOIC, operates
from a single +9 V supply, and has an operational temperature
range of –40∞C to +85∞C.
The AD8321 is a low cost digitally controlled variable gain
amplifier optimized for coaxial line driving applications such as
cable modems that are designed to the DOCSIS* (upstream)
standard. An 8-bit serial word determines the desired output gain
over a 53.4 dB range, resulting in gain changes of 0.75 dB/LSB.
–40
f
= 42MHz
O
V
= 137mV p-p
IN
(P = –15dBm)
IN
The AD8321 comprises a digitally controlled variable attenuator
of 0 dB to –53.4 dB, which is preceded by a low noise, fixed
gain buffer and followed by a low distortion high power ampli-
fier. The AD8321 accepts a differential or single-ended input
signal. The output is specified for driving a 75 W load, such as
coaxial cable, although the AD8321 is capable of driving other
loads. Performance of –53 dBc is achieved with an output level
up to 11 dBm at 42 MHz bandwidth using a 9 V supply.
–50
–60
(P
= 11dBm @
OUT
MAX GAIN)
HD3
HD2
–70
–80
–90
A key performance and cost advantage of the AD8321 results
from the ability to maintain a constant 75 W output impedance
during power-up and power-down conditions. This eliminates
the need for external 75 W termination, resulting in twice the
effective output voltage when compared to a standard opera-
tional amplifier, thus eliminating the need for a transformer.
0
8
16
24
32
40
48
56
64
72
GAIN CONTROL – Decimal
Figure 1. Harmonic Distortion vs. Gain Control
*Data-Over-Cable Service Interface Specifications
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. 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: 781/329-4700
Fax: 781/461-3113
www.analog.com
© 2005 Analog Devices, Inc. All rights reserved.
5秒后页面跳转
74LS32芯片参数、引脚图及功能真值表
全球首块英伟达H200交付 黄仁勋“送货上门”
常用8脚开关电源芯片型号大全
74HC04芯片引脚图及功能、应用电路图讲解
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
