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Teilenummer | DS42BR400 |
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Beschreibung | Quad 4.25 Gbps CML Transceiver | |
Hersteller | National Semiconductor | |
Logo | ||
Gesamt 14 Seiten March 27, 2008
DS42BR400
Quad 4.25 Gbps CML Transceiver with Transmit
De-Emphasis and Receive Equalization
General Description
The DS42BR400 is a quad 250 Mbps – 4.25 Gbps CML
transceiver, or 8-channel buffer, for use in backplane and ca-
ble applications. With operation down to 250 Mbps, the
DS42BR400 can be used in applications requiring both low
and high frequency data rates. Each input stage has a fixed
equalizer to reduce ISI distortion from board traces. The
equalizers are grouped in fours and are enabled through two
www.DcaotnatSrohlepeint4sU. .Tchoemse control pins provide customers flexibility
where ISI distortion may vary from one direction to another.
All output drivers have four selectable steps of de-emphasis
to compensate against transmission loss across long FR4
backplanes. The de-emphasis blocks are also grouped in
fours. In addition, the DS42BR400 also has loopback control
capability on four channels. All CML drivers have 50Ω termi-
nation to VCC. All receivers are internally terminated with
differential 100Ω.
Features
■ 250 Mbps – 4.25 Gbps Fully Differential Data Paths
■ Optional Fixed Input Equalization
■ Selectable Output De-emphasis
■ Individual Loopback Controls
■ On-chip Termination
■ Lead-less eLLP-60 pin package (9 mm x 9 mm x 0.8 mm,
0.5 mm pitch)
■ −40°C to +85°C Industrial Temperature Range
■ 6 kV ESD Rating, HBM
Applications
■ Backplane driver or cable driver
■ Signal repeating, buffering and conditioning applications
Simplified Application Diagram
20182440
© 2008 National Semiconductor Corporation 201824
www.national.com
Functional Description
TABLE 1. Logic Table for Loopback Controls
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LB0
0
1 (default)
LB1
0
1 (default)
LB2
0
1 (default)
LB3
0
1 (default)
Loopback Function
Enable loopback from IB_0± to OA_0±.
Normal mode. Loopback disabled.
Loopback Function
Enable loopback from IB_1± to OA_1±.
Normal mode. Loopback disabled.
Loopback Function
Enable loopback from IB_2± to OA_2±.
Normal mode. Loopback disabled.
Loopback Function
Enable loopback from IB_3± to OA_3±.
Normal mode. Loopback disabled.
TABLE 2. De-Emphasis Controls
PreA_[1:0]
00
01
10
1 1 (Default)
PreB_[1:0]
00
01
10
1 1 (Default)
Default VOD Level in mVPP
(VODB)
1200
1200
1200
1200
Default VOD Level in mVPP
(VODB)
1200
1200
1200
1200
De-Emphasis Level in mVPP De-Emphasis in dB (VODPE/
(VODPE)
VODB)
1200
0
850 −3
600 −6
426 −9
De-Emphasis Level in mVPP De-Emphasis in dB (VODPE/
(VODPE)
VODB)
1200
0
850 −3
600 −6
426 −9
De-emphasis is the primary signal conditioning function for
use in compensating against backplane transmission loss.
The DS42BR400 provides four steps of de-emphasis ranging
from 0, −3, −6 and −9 dB, user-selectable dependent on the
loss profile of the backplane. Figure 1 shows a driver de-em-
phasis waveform. The de-emphasis duration is nominal 200
ps, corresponding to 85% bit-width at 4.25 Gbps. The de-em-
phasis levels of switch-side and line-side can be individually
programmed.
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6 Page www.DataSheet4U.com
FIGURE 5. Output De-Emphasis Duration
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FIGURE 6. AC Test Circuit
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20182441
FIGURE 7. Receiver Input Termination
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12 Page | ||
Seiten | Gesamt 14 Seiten | |
PDF Download | [ DS42BR400 Schematic.PDF ] |
Teilenummer | Beschreibung | Hersteller |
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