AD8324_05 Datasheet, PDF (1/16 Pages) Analog Devices – 3.3 V Upstream Cable Line Driver

FEATURES
Supports DOCSIS 2.0 and Euro-DOCSIS standards for
reverse path transmission systems
Gain programmable in 1 dB steps over a 59 dB range
Low distortion at 61 dBmV output:
–59 dBc SFDR at 21 MHz
–54 dBc SFDR at 65 MHz
Output noise level @ minimum gain 1.3 nV/√Hz
Maintains 75 Ω output impedance in TX-enable and
Transmit-disable condition
Upper bandwidth: 100 MHz (full gain range)
3.3 V supply operation
Supports SPI® interfaces
APPLICATIONS
DOCSIS 2.0 and Euro-DOCSIS cable modems
CATV set-top boxes
CATV telephony modems
Coaxial and twisted pair line drivers
GENERAL DESCRIPTION
The AD8324¹ is a low cost amplifier designed for coaxial line
driving. The features and specifications make the AD8324
ideally suited for DOCSIS 2.0 and Euro-DOCSIS applications.
The gain of the AD8324 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 AD8324 accepts a differential or single-ended input signal.
The output is specified for driving a 75 Ω load through a 1:1
transformer.
Distortion performance of –54 dBc is achieved with an output
level up to 61 dBmV at 65 MHz bandwidth.
This device has a sleep mode function that reduces the quies-
cent current to 30 μA and a full power-down function that
reduces power-down current to 2.5 mA.
The AD8324 is packaged in a low cost 20-lead LFCSP package
and a 20-lead QSOP package. The AD8324 operates from a
single 3.3 V supply.
3.3 V Upstream
Cable Line Driver
AD8324
FUNCTIONAL BLOCK DIAGRAM
BYP
V_IN+
V_IN–
DIFF
OR SINGLE
INPUT
AMP
VERNIER
Z_IN (SINGLE) = 550Ω
Z_IN (DIFF) = 1100Ω
AD8324
ATTENUATION
CORE
8
V_OUT+
OUTPUT
STAGE
Z_OUT DIFF =
75Ω
V_OUT–
DECODE
8
DATA LATCH
POWER-
DOWN LOGIC
RAMP
8
SHIFT
REGISTER
GND DATEN DATA CLK
TXEN SLEEP
Figure 1. Functional Block Diagram
–40
–50
V_OUT = 61dBmV @ DEC 60
THIRD HARMONIC
–60
V_OUT = 61dBmV @ DEC 60
–70
SECOND HARMONIC
–80
5
15
25
35
45
55
65
FREQUENCY (MHz)
Figure 2. Worst Harmonic Distortion vs. Frequency
1 _{Patent pending.}
Rev. A
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