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PDF DS25MB100 Data sheet ( Hoja de datos )
| Número de pieza | DS25MB100 | |
| Descripción | 2.5 Gbps 2:1/1:2 CML Mux/Buffer | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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December 6, 2007
DS25MB100
2.5 Gbps 2:1/1:2 CML Mux/Buffer with Transmit De-
Emphasis and Receive Equalization
General Description
The DS25MB100 is a signal conditioning 2:1 multiplexer and
1:2 fan-out buffer designed for use in backplane redundancy
or cable driving applications. Signal conditioning features in-
clude input equalization and programmable output de-em-
phasis that enable data communication in FR4 backplane up
to 2.5 Gbps. Each input stage has a fixed equalizer to reduce
ISI distortion from board traces. All output drivers have four
www.DsaetlaecSthaebelet4lUe.vceolsmof de-emphasis to compensate for trans-
mission losses from long FR4 backplane or cable attenuation
reducing deterministic jitter. The de-emphasis levels can be
independently controlled for the line-side and switch-side
drivers. The internal loopback paths from switch-side input to
switch-side output enable at-speed system testing. All receiv-
er inputs and driver outputs are internally terminated with
100Ω differential terminating resistors.
Features
■ 2:1 multiplexer and 1:2 buffer
■ 0.25–2.5 Gbps fully differential data paths
■ Fixed input equalization
■ Programmable output de-emphasis
■ Independent de-emphasis controls
■ Programmable loopback modes
■ On-chip terminations
■ HBM ESD rating 5.5 kV on all pins
■ +3.3V supply
■ Low power, 0.45 W typical
■ Lead-less LLP-36 package
■ −40°C to +85°C operating temperature range
Applications
■ Backplane or cable driver
■ Redundancy and signal conditioning applications
■ CPRI/OBSAI
Functional Block Diagram
© 2007 National Semiconductor Corporation 202089
20208901
www.national.com
1 page  
Functional Description
The DS25MB100 is a signal conditioning 2:1 multiplexer and
a 1:2 buffer designed to support port redundancy up to 2.5
Gbps. Each input stage has a fixed equalizer that provides
equalization to compensate about 5 dB of transmission loss
from a short backplane trace (about 10 inches backplane).
The output driver has de-emphasis (driver-side equalization)
to compensate the transmission loss of the backplane that it
is driving. The driver conditions the output signal such that the
lower frequency and higher frequency pulses reach approxi-
mately the same amplitude at the end of the backplane, and
minimize the deterministic jitter caused by the amplitude dis-
parity. The DS25MB100 provides four steps of user-se-
lectable de-emphasis ranging from 0, -3, -6 and –9 dB to
handle different lengths of backplane. Figure 1 shows a driver
de-emphasis waveform. The de-emphasis duration is 188ps
nominal, corresponds to 0.47 bit-width at 2.5 Gbps. The de-
emphasis levels of switch-side and line-side can be individu-
ally programmed.
wwThwe.DhaigthaSshpeeeedt4iUn.pcuotsmare self-biased to about 1.3V and are
designed for AC coupling. The inputs are compatible to most
AC coupling differential signals such as LVDS, LVPECL and
CML.
TABLE 1. Logic Table For Multiplex Controls
MUX_S0 Mux Function
0 MUX select switch input, IN1±.
1 MUX select switch input, IN0±.
(default)
TABLE 2. Logic Table For Loopback Controls
LB0 Loopback Function
0 Enable loopback from IN0± to OUT0±.
1 Normal mode. Loopback disabled.
(default)
LB1 Loopback Function
0 Enable loopback from IN1± to OUT1±.
1 Normal mode. Loopback disabled.
(default)
TABLE 3. Line-Side De-Emphasis Controls
DEL_[1:0]
00
01
10
1 1 (default)
De-Emphasis
Level in mVPP
(VODB)
1300
1300
1300
1300
De-Emphasis
Level in mVPP
(VODPE)
1300
920
650
461
De-Emphasis in dB
(VODPE/VODB)
Typical FR4 Board Trace
0 10 inches
−3 20 inches
−6 30 inches
−9 40 inches
DES_[1:0]
00
01
10
1 1 (default)
TABLE 4. Switch-Side De-Emphasis Controls
De-Emphasis
Level in mVPP
(VODB)
1300
1300
1300
1300
De-Emphasis
Level in mVPP
(VODPE)
1300
920
650
461
De-Emphasis in dB
(VODPE/VODB)
0
−3
−6
−9
Typical FR4 Board Trace
10 inches
20 inches
30 inches
40 inches
0
1 (default)
EQL/EQS
TABLE 5. EQ Controls For Line And Switch Sides
Loopback Function
Enable equalization.
Normal mode. Equalization disabled.
5 www.national.com
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FIGURE 5. AC Test Circuit
20208908
11 www.national.com
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet DS25MB100.PDF ] | |
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