5 V Upstream
Cable Line Driver
AD8328
FEATURES
FUNCTIONAL BLOCK DIAGRAM
BYP
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
AD8328
DIFF
V
V
V
V
IN+
OUT+
OR
POWER
AMP
ATTENUATION
SINGLE
INPUT
AMP
VERNIER
CORE
−54 dBc SFDR at 65 MHz
IN–
OUT–
Z
DIFF =
OUT
300Ω
8
Output noise level @ minimum gain 1.2 nV/√Hz
Maintains 300 Ω output impedance Tx-enable and
Tx-disable condition
Z
Z
(SINGLE) = 800Ω
(DIFF) = 1.6kΩ
IN
IN
DECODE
POWER-DOWN
LOGIC
8
RAMP
DATA LATCH
Upper bandwidth: 107 MHz (full gain range)
5 V supply operation
Supports SPI interfaces
8
SHIFT
REGISTER
APPLICATIONS
GND
DATEN SDATA CLK
TXEN
SLEEP
DOCSIS and EuroDOCSIS cable modems
CATV set-top boxes
Figure 1.
CATV telephony modems
Coaxial and twisted pair line drivers
GENERAL DESCRIPTION
–50
The AD83281 is a low cost amplifier designed for coaxial line
driving. The features and specifications make the AD8328
ideally suited for MCNS-DOCSIS and EuroDOCSIS applications.
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.
–52
–54
–56
–58
–60
–62
–64
–66
–68
–70
V
= 60dBmV
OUT
@ MAX GAIN,
THIRD HARMONIC
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.
V
= 60dBmV
OUT
@ MAX GAIN,
SECOND HARMONIC
Distortion performance of −53 dBc is achieved with an output
level up to 60 dBmV at 65 MHz bandwidth over a wide
temperature range.
5
15
25
35
45
55
65
FREQUENCY (MHz)
Figure 2. Worst Harmonic Distortion vs. Frequency
1 Patent pending.
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 and
a 20-lead QSOP. The AD8328 operates from a single 5 V supply
and has an operational temperature range of −40°C to +85°C.
Rev. A
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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