DP83848TSQ/NOPB National Semiconductor, DP83848TSQ/NOPB Datasheet - Page 27

IC TXRX ETHERNET PHYTER 40-LLP

DP83848TSQ/NOPB

Manufacturer Part Number
DP83848TSQ/NOPB
Description
IC TXRX ETHERNET PHYTER 40-LLP
Manufacturer
National Semiconductor
Type
Transceiverr
Datasheets

Specifications of DP83848TSQ/NOPB

Number Of Drivers/receivers
1/1
Protocol
Ethernet
Voltage - Supply
3 V ~ 3.6 V
Mounting Type
Surface Mount
Package / Case
40-LLP
Data Rate
100Mbps
Supply Voltage Range
3V To 3.6V
Logic Case Style
LLP
No. Of Pins
40
Operating Temperature Range
-40°C To +85°C
Msl
MSL 2 - 1 Year
Filter Terminals
SMD
Rohs Compliant
Yes
Data Rate Max
10Mbps
Driver Case Style
LLP
For Use With
DP83848T-MAU-EK - BOARD EVALUATION DP83848T
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
DP83848TSQTR

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0
4.2.2.1 Digital Adaptive Equalization and Gain Control
When transmitting data at high speeds over copper
twisted pair cable, frequency dependent attenuation
becomes a concern. In high-speed twisted pair signalling,
the frequency content of the transmitted signal can vary
greatly during normal operation based primarily on the
randomness of the scrambled data stream. This variation
in signal attenuation caused by frequency variations must
be compensated to ensure the integrity of the transmis-
sion.
In order to ensure quality transmission when employing
MLT-3 encoding, the compensation must be able to adapt
to various cable lengths and cable types depending on the
installed environment. The selection of long cable lengths
for a given implementation, requires significant compen-
sation which will over-compensate for shorter, less attenu-
ating lengths. Conversely, the selection of short or
intermediate cable lengths requiring less compensation
will cause serious under-compensation for longer length
cables. The compensation or equalization must be adap-
Figure 8. EIA/TIA Attenuation vs. Frequency for 0, 50,
100, 130 & 150 meters of CAT 5 cable
27
tive to ensure proper conditioning of the received signal
independent of the cable length.
The DP83848H utilizes an extremely robust equalization
scheme referred as ‘Digital Adaptive Equalization.’
The Digital Equalizer removes ISI (inter symbol interfer-
ence) from the receive data stream by continuously adapt-
ing to provide a filter with the inverse frequency response
of the channel. Equalization is combined with an adaptive
gain control stage. This enables the receive 'eye pattern'
to be opened sufficiently to allow very reliable data recov-
ery.
The curves given in Figure 8 illustrate attenuation at cer-
tain frequencies for given cable lengths. This is derived
from the worst case frequency vs. attenuation figures as
specified in the EIA/TIA Bulletin TSB-36. These curves
indicate the significant variations in signal attenuation that
must be compensated for by the receive adaptive equal-
ization circuit.
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