ANALOGDEVICES fAX-ON-DEMAND HOTLINE
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~ ANALOG
W DEVICES
Precision, ideband
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Channel rocessing
P
Element
FEATURES
An 80MHz Bandwidth Permitting a 50Mb/s Data
Transfer Rate
A Variable Gain Amplifier with JOdB max Gain
and 40dB Control Range
Two Gain of 4 RF Buffers
200n Differential load Drive Capability
A Pair of Precision Rectifiers
AGC level and Threshold Outputs
An Averaging, High Gain Sample-and-Hold for
Accurate AGC Operation
Typical Gain Drift in Hold Mode: 0.2dB/ms
Gains Trimmed and Temperature Compensated
AGC Operation Independent of AGC level
Symmetrical AGC Attack/Decay Times
1J.ls AGC Attack/Decay Times Using a 1000pF
External Capacitor
Suitable for Use as an Accurate Video Programmable
Gain Amplifier
Dynamic Clamp Ensures Fast Recovery After Write to
Read Transients
AGC RF Output level is Internally Preset
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11\.0890
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PRODUCT DESCRIPTION
The AD890 is primarily intended for high-performance disk
subsystem use and as such it is configured around the classic
read channel processing block diagram. It is intended to be
connected between the head preamplifier and the qualification
circuitry required for digital data recovery. When used with the
A0891 rigid disk data qualifier, data transfer rates in excess of
SOMb/s can be processed.
A temperature-compensated AGC loop, with an exponential
transfer characteristic, permits optimal settling and allows for
predictable performance in the classic single integrator control
loop configuration. Fast acquisition and low droop while in the
hold mode allow for AGC operation to be performed within the
sector header without compromising channel behavior when
reading data.
Threshold" output may be used lor creating a dara qualification
level. A second rectifier is used to drive the sample-and-hold
circuitry.
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The 80MHz bandwidth of the A0890 ensures good phase linearity
up to SOMHz. Thus, data transfer rates in excess of SOMbfscan
be supported with good error rates and predictable channel
behavior.
The AD890 is available in both a 24-pill, slim-line cerdip package
and in a 28-pin PLCC package and is specified to operarc over
the 0 to 70DCcommercial temperatUre range.
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The AD890 processing clement has the flexibility to perform
both continuous and sampled AGC functions; it is also ideal for
embedded, dedicated, or mixed servo applications. Two userdefined filter/equalizer stages may be employed, thus allowing
maximum design flexibility. This greatly simplifies the design of
the overall channel characteristics. Using the AD890, the designer
no longer needs to resort 10 passive techniques to isolate network
functions; this avoids problems of signal loss and interaction.
Two low-offset, IOOMHzfull-wave rectifiers provide the capability
to track a 1V peak signal. The rectifier generating the "Qualifier
Information
furnished
by Analog Devicl!$ is believed to be
and reliable. However, no responsibility
is assumed by Analog
for its use; nor for any infringements
of patents or other rights
parties which may result from its use. No license is granted by
tion or otherwise under any patent or patent rights of Analog
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Functional Block Diagram
One Tec:hnology Way; P. O. Box 9106; Norwood, MA 02062-9106
Tel: 617/329-4700
TWX: 710/394-6577
West Coast
Central
Atlantic
714/641-9391
214/231-5094
215/643-7790