AD8328_05 Datasheet, PDF (1/20 Pages) Analog Devices – 5 V Upstream Cable Line Driver

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 Ω output impedance Tx-enable and
Tx-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 drivers
GENERAL DESCRIPTION
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.
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
temperature 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 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.
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) = 800Ω
Z_IN (DIFF) = 1.6kΩ
ATTENUATION
CORE
8
DECODE
POWER
AMP
Z_OUT DIFF =
300Ω
V_OUT+
V_OUT–
8
POWER-DOWN
DATA LATCH
LOGIC
RAMP
8
SHIFT
REGISTER
GND
DATEN SDATA CLK
Figure 1.
TXEN SLEEP
–50
–52
V_OUT = 60dBmV
–54
@ MAX GAIN,
THIRD HARMONIC
–56
–58
–60
–62
V_OUT = 60dBmV
–64
@ MAX GAIN,
SECOND HARMONIC
–66
–68
–70
5
15
25
35
45
FREQUENCY (MHz)
55
65
Figure 2. Worst Harmonic Distortion vs. Frequency
1 _{Patent pending.}
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, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. 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: [phone]
www.analog.com
Fax: [phone]
© 2005 Analog Devices, Inc. All rights reserved.