AD8325,AD8325ARU,AD8325ARU,AD8325ARU-REEL,AD8325ARU-REEL,AD8325-EVAL

Part No.:
AD8325,AD8325ARU,AD8325ARU,AD8325ARU-REEL,AD8325ARU-REEL,AD8325-EVAL
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Description:
5 V CATV Line Driver Fine Step Output Power Control
File Size:
305 K
Page:
16 Pages
Logo:
Maker:
AD [ ANALOG DEVICES ]
PCB Prototype

July 19, 2018:

ADAU1979

ADC121S655CIMMX

ADN4694E

ADP3303ARZ-3.3

ADS1198

ADS54T01

ADSP-21366SKBC-ENG

ADT7302ARTZ-REEL7

ADT7485AARMZ-REEL7

ADUM5400CRWZ2

ADV7850KBCZ-5

AEQ75Y48N-63

PCB Datasheet:1PCB Datasheet:1
a
FEATURES
Supports DOCSIS Standard for Reverse Path
Transmission
Gain Programmable in 0.75 dB Steps Over a 59.45 dB
Range
Low Distortion at 61 dBmV Output
–57 dBc SFDR at 21 MHz
–55 dBc SFDR at 42 MHz
Output Noise Level
–48 dBmV in 160 kHz
Maintains 75 Output Impedance
Transmit Enable and Transmit Disable Modes
Upper Bandwidth: 100 MHz (Full Gain Range)
5 V Supply Operation
Supports SPI Interfaces
APPLICATIONS
Gain-Programmable Line Driver
DOCSIS High-Speed Data Modems
Interactive Cable Set-Top Boxes
PC Plug-in Cable Modems
General-Purpose Digitally Controlled Variable Gain Block
V
IN+
5 V CATV Line Driver Fine Step
Output Power Control
AD8325
FUNCTIONAL BLOCK DIAGRAM
V
CC
(7 PINS)
BYP
R1
AD8325
V
OUT+
VERNIER
ATTENUATION
CORE
V
IN–
DIFF OR
SINGLE
INPUT
AMP
POWER
AMP
V
OUT–
Z
OUT
DIFF =
75
8
R2
Z
IN
(SINGLE) = 800
Z
IN
(DIFF) = 1.6k
DECODE
8
DATA LATCH
8
SHIFT
REGISTER
POWER-DOWN
LOGIC
DATEN
DATA
CLK
GND (11 PINS) TXEN
SLEEP
GENERAL DESCRIPTION
The AD8325 is a low-cost, digitally controlled, variable gain ampli-
fier 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 output gain
over a 59.45 dB range resulting in gain changes of 0.7526 dB/LSB.
DISTORTION – dBc
–50
V
OUT
= 62dBmV
@ MAX GAIN
–52
V
OUT
= 61dBmV
@ MAX GAIN
–54
The AD8325 comprises a digitally controlled variable attenuator
of 0 dB to –59.45 dB, which is preceded by a low noise, fixed
gain buffer and is followed by a low distortion high power ampli-
fier. The AD8325 accepts a differential or single-ended input
signal. The output is specified for driving a 75
load, such as
coaxial cable.
Distortion performance of –57 dBc is achieved with an output
level up to 61 dBmV at 21 MHz bandwidth. A key performance
and cost advantage of the AD8325 results from the ability to
maintain a constant 75
output impedance during Transmit
Enable and Transmit Disable conditions. In addition, this
device has a sleep mode function that reduces the quiescent
current to 4 mA.
The AD8325 is packaged in a low-cost 28-lead TSSOP, operates
from a single 5 V supply, and has an operational temperature
range of –40°C to +85°C.
–56
–58
–60
–62
V
OUT
= 59dBmV
@ MAX GAIN
–64
5
15
25
35
45
55
FUNDAMENTAL FREQUENCY – MHz
65
V
OUT
= 60dBmV
@ MAX GAIN
Figure 1. Worst Harmonic Distortion vs. Gain Control
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