AD8328 Datasheet, PDF (1/16 Pages) Analog Devices – 5 V Upstream Cable Line Driver

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FEATURES
Supports DOCSIS and EuroDOCSIS Standards for
Reverse Path Transmission Systems
Gain Programmable in 1 dB Steps over a 59 dB Range
Low Distortion at 60 dBmV Output:
–57.5 dBc SFDR at 21 MHz
–54 dBc SFDR at 65 MHz
Output Noise Level @ Minimum Gain 1.2 nV/√Hz
Maintains 300 ⍀ Output Impedance TX-Enable and
Transmit-Disable Condition
Upper Bandwidth: 107 MHz (Full Gain Range)
5 V Supply Operation
Supports SPI Interfaces
APPLICATIONS
DOCSIS and EuroDOCSIS Cable Modems
CATV Set-Top Boxes
CATV Telephony Modems
Coaxial and Twisted Pair Line Driver
5 V Upstream
Cable Line Driver
AD8328^*
FUNCTIONAL BLOCK DIAGRAM
BYP
AD8328
V_IN+
V_IN–
DIFF OR
SINGLE
INPUT
AMP
VERNIER
Z_IN (SINGLE) = 800⍀
Z_IN (DIFF) = 1.6k⍀
ATTENUATION
CORE
8
DECODE
POWER
AMP
Z_OUT DIFF =
300⍀
V_OUT+
V_OUT–
8
DATA LATCH
POWER-DOWN
LOGIC
RAMP
8
SHIFT
REGISTER
GND DATEN SDATA CLK
TXEN SLEEP
GENERAL DESCRIPTION
The AD8328 is a low cost amplifier designed for coaxial line
driving. The features and specifications make the AD8328
ideally suited for MCNS-DOCSIS and Euro-DOCSIS applica-
tions. The gain of the AD8328 is digitally controlled. An 8-bit
serial word determines the desired output gain over a 59 dB range,
resulting in gain changes of 1 dB/LSB.
The AD8328 accepts a differential or single-ended input signal. The
output is specified for driving a 75 Ω load through a 2:1 transformer.
Distortion performance of –53 dBc is achieved with an output
level up to 60 dBmV at 65 MHz bandwidth over a wide tempera-
ture range.
This device has a sleep mode function that reduces the quiescent
current to 2.6 mA and a full power-down function that reduces
power-down current to 20 µA.
The AD8328 is packaged in a low cost 20-lead LFCSP package
and a 20-lead QSOP package. The AD8328 operates from a single
5 V supply and has an operational temperature range of –40°C
to +85°C.
–50
–52
–54
V_OUT = 60dBmV
@MAX GAIN,
–56
THIRD HARMONIC
–58
–60
–62
V_OUT = 60 dBmV
–64
@MAX GAIN,
SECOND HARMONIC
–66
–68
–70
5
15
25
35
45
55
65
FREQUENCY – MHz
Figure 1. Worst Harmonic Distortion vs. Frequency
*Patent Pending
REV. 0
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© Analog Devices, Inc., 2002