REV. 0

a

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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

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

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

5V supply and has an operational temperature range of –40

°C

to +85

°C.

FUNCTIONAL BLOCK DIAGRAM

DIFF OR

SINGLE

INPUT

AMP

ATTENUATION

CORE

300

8

8

8

AD8328

DATEN SDATA CLK

TXEN

SLEEP

VERNIER

DECODE

DATA LATCH

SHIFT

REGISTER

POWER-DOWN

LOGIC

POWER

AMP

BYP

GND

RAMP

5

15

25

35

45

55

65

FREQUENCY – MHz

@MAX GAIN,

THIRD HARMONIC

@MAX GAIN,

SECOND HARMONIC

–70

–68

–66

–64

–62

–60

–58

–56

–54

–52

–50

Figure 1. Worst Harmonic Distortion vs. Frequency

*Patent Pending