DS25MB100
2.5 Gb/s 1:2 Mux/Buffer with Input Equalization and Output
De-Emphasis
General Description
Features
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 include input equalization and programmable output de-emphasis 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
selectable levels of de-emphasis to compensate for transmission 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 receiver inputs and driver outputs are internally terminated with
100Ω differential terminating resistors.
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■
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■
■
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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
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■
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Backplane driver or cable driver
Redundancy and signal conditioning applications
PCI Express
Serial ATA
CPRI/OBSAI
Functional Block Diagram
20208901
© 2007 National Semiconductor Corporation
202089
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DS25MB100 2.5 Gb/s 1:2 Mux/Buffer with Input Equalization and Output De-Emphasis
March 2007
DS25MB100
Simplified Block Diagram
20208902
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2
DS25MB100
Connection Diagram
20208903
Order Number DS25MB100TSQ
See NS Package Number SQA36A
3
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DS25MB100
Pin Descriptions
Pin Name
Pin Number
I/O
Description
LINE SIDE HIGH SPEED DIFFERENTIAL IO's
IN+
IN−
33
34
I
Inverting and non-inverting differential inputs at the line side. IN+ and IN− have an internal 50Ω
connected to an internal reference voltage.
OUT+
OUT−
30
31
O
Inverting and non-inverting differential outputs at the line side. OUT+ and OUT− have an internal
50Ω connected to VCC.
SWITCH SIDE HIGH SPEED DIFFERENTIAL IO's
OUT0+
OUT0−
3
4
O
Inverting and non-inverting differential outputs of mux0 at the switch side. OUT0+ and OUT0− have
an internal 50Ω connected to VCC.
OUT1+
OUT1−
22
21
O
Inverting and non-inverting differential outputs of mux1 at the switch side. OUT1+ and OUT1− have
an internal 50Ω connected to VCC.
IN0+
IN0−
6
7
I
Inverting and non-inverting differential inputs to the mux at the switch side. IN0+ and IN0− have
an internal 50Ω connected to an internal reference voltage.
IN1+
IN1−
25
24
I
Inverting and non-inverting differential inputs to the mux at the switch side. IN1+ and IN1− have
an internal 50Ω connected to an internal reference voltage.
CONTROL (3.3V LVCMOS)
MUX
19
I
A logic low at MUX_S0 selects mux_0 to switch B. MUX_S0 is internally pulled high. Default state
for mux_0 is switch A.
EQL
11
I
A logic low enables the EQ. EQL is internally pulled high. Default is with EQ disabled.
EQS
36
I
A logic low enables the EQ. EQS is internally pulled high. Default is with EQ disabled.
DEL_0
DEL_1
18
27
I
DEL_0 and DEL_1 select the output de-emphasis of the line side drivers (OUT±).
DEL_0 and DEL_1 are internally pulled high.
DES_0
DES_1
10
1
I
DES_0 and DES_1 select the output de-emphasis of the switch side drivers (OUT0±, OUT1±).
DES_0 and DES_1 are internally pulled high.
LB0
28
LB1
26
I
A logic low at LB1 enables the internal loopback path from IN1± to OUT1±. LB1 is internally pulled
high.
RSV
17
I
Reserve pin to support factory testing. This pin can be left open, or tied to GND, or tied to GND
through an external pull-down resistor.
5, 13, 15, 23,
32
P
VCC = 3.3V ± 5%. The maximum current consumption under worst voltage, temperature, and
process variation conditions does not exceed 170mA.
Each VCC pin should be connected to the VCC plane through a low inductance path, typically with
a via located as close as possible to the landing pad of the VCC pin.
A logic low at LB0 enables the internal loopback path from IN0± to OUT0±. LB0 is internally pulled
high.
POWER
VCC
It is recommended to have a 0.01 μF or 0.1 μF, X7R, size-0402 bypass capacitor from each VCC
pin to ground plane.
GND
2, 8, 9, 12,
14, 16, 20,
29, 35
P
Ground reference. Each ground pin should be connected to the ground plane through a low
inductance path, typically with a via located as close as possible to the landing pad of the GND
pin.
GND
DAP
P
DAP is the metal contact at the bottom side, located at the center of the LLP package. It should
be connected to the GND plane with at least 16 via to lower the ground impedance and improve
the thermal performance of the package.
Note: I=Input, O=Output, P=Power
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4
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 approximately the same amplitude at the end of the backplane, and
minimize the deterministic jitter caused by the amplitude disparity. The DS25MB100 provides four steps of user-selectable 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 deemphasis levels of switch-side and line-side can be individually programmed.
The high speed inputs are self-biased to about 1.3V and are
designed for AC coupling. The inputs are compatible to most
TABLE 1. Logic Table For Multiplex Controls
MUX_S0 Mux Function
0
MUX select switch input, IN1±.
1
(default)
MUX select switch input, IN0±.
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
De-Emphasis
Level in mVPP
(VODB)
DEL_[1:0]
De-Emphasis
Level in mVPP
(VODPE)
De-Emphasis in dB
(VODPE/VODB)
Typical FR4 Board Trace
00
1300
1300
0
10 inches
01
1300
920
−3
20 inches
10
1300
650
−6
30 inches
1 1 (default)
1300
461
−9
40 inches
TABLE 4. Switch-Side De-Emphasis Controls
De-Emphasis
Level in mVPP
(VODB)
DES_[1:0]
De-Emphasis
Level in mVPP
(VODPE)
De-Emphasis in dB
(VODPE/VODB)
Typical FR4 Board Trace
00
1300
1300
0
10 inches
01
1300
920
−3
20 inches
10
1300
650
−6
30 inches
1 1 (default)
1300
461
−9
40 inches
TABLE 5. EQ Controls For Line And Switch Sides
EQL/EQS
Loopback Function
0
Enable equalization.
1 (default)
Normal mode. Equalization disabled.
5
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DS25MB100
AC coupling differential signals such as LVDS, LVPECL and
CML.
Functional Description
DS25MB100
20208904
FIGURE 1. Driver De-Emphasis Differential Waveform (Showing All 4 De-Emphasis Steps)
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6
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (VCC)
CMOS/TTL Input Voltage
CML Input/Output Voltage
Junction Temperature
Storage Temperature
Lead Temperature
Soldering, 4 seconds
−0.3V to 4V
−0.3V to (VCC +0.3V)
−0.3V to (VCC +0.3V)
+150°C
−65°C to +150°C
Supply Voltage (VCC-GND)
Min Typ
Max
Units
3.13 3.3
5
3.465
V
100
mVPP
85
°C
100
°C
Supply Noise Amplitude
10 Hz to 2 GHz
26.2°C/W
Thermal Resistance, θJC-top
6 kV
1.25 kV
350V
Recommended Operating Ratings
+260°C
Thermal Resistance, θJA (Note 8)
11.1°C/W
Ambient Temperature
3.3°C/W
–40
Case Temperature
Electrical Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
(Note 2)
Max
Units
2.0
VCC
+0.3
V
−0.3
0.8
V
10
µA
124
µA
LVCMOS DC SPECIFICATIONS
VIH
High Level Input Voltage
VIL
Low Level Input Voltage
IIH
High Level Input Current
VIN = VCC
−10
IIL
Low Level Input Current
VIN = GND
75
RPU
Pull-High Resistance
94
35
kΩ
RECEIVER SPECIFICATIONS
VID
Differential Input Voltage AC Coupled Differential Signal
Range (Note 9)
Below 1.25 Gbps
Above 1.25 Gbps
This parameter is not tested at production
VICM
Common Mode Voltage at Measured at receiver inputs reference to ground
Receiver Inputs
RITD
Input Differential
Termination (Note 3)
RITSE
Input Termination (single- On-chip termination IN+ or IN− to GND for frequency
end)
> 100 MHz
On-chip differential termination between IN+ or IN−
100
100
1750
1560
1.3
84
100
mVP-P
mVP-P
V
116
Ω
Ω
50
DRIVER SPECIFICATIONS
VODB
VDE
Output Differential
Voltage Swing
withoutdDe-Emphasis
(Note 4)
RL = 100Ω ±1%
DES_1=DES_0=0
DEL_1=DEL_0=0
Driver De-emphasis disabled
Running K28.7 pattern at 2.5 Gbps
See Figure 5 for test circuit.
Output De-Emphasis
Voltage Ratio
20*log(VDODPE/VODB)
RL = 100Ω ±1%
Running K28.7 pattern at 2.5 Gbps
DEx_[1:0]=00
DEx_[1:0]=01
PREx_[1:0]=10
DEx_[1:0]=11
x=S for switch side de-emphasis control
x=L for line side de-emphasis control
See Figure 1 on waveform.
See Figure 5 for test circuit.
7
1100
1300
1500
mVP-P
0
−3
−6
−9
dB
dB
dB
dB
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DS25MB100
Thermal Resistance, ΦJB
ESD Rating (Note 10)
HBM, 1.5 kΩ, 100 pF
CDM
MM
Absolute Maximum Ratings (Note 1)
DS25MB100
Min
Typ
(Note 2)
Max
Units
Tested at −9 dB de-emphasis level, DEx[1:0]=11
x=S for switch side de-emphasis control
x=L for line side de-emphasis control
See Figure 4 on measurement condition.
125
188
250
ps
ROTSE
Output Termination (Note On-chip termination from OUT+ or OUT− to VCC
3)
42
50
58
Ω
ROTD
Output Differential
Termination
On-chip differential termination between OUT+ and
OUT−
ΔROTSE
Mis-Match in Output
Termination Resistors
Mis-match in output terminations at OUT+ and OUT−
VOCM
Output Common Mode
Voltage
Symbol
TDE
Parameter
De-Emphasis Width
Conditions
Ω
100
5
%
2.7
V
0.45
W
100
ps
100
ps
POWER DISSIPATION
PD
Power Dissipation
VDD = 3.3V @ 25°C
All outputs terminated by 100Ω ±1%.
DEL_[1:0]=0, DES_[1:0]=0
Running PRBS 27-1 pattern at 2.5 Gbps
AC CHARACTERISTICS
tR
Differential Low to High
Transition Time
tF
Differential High to Low
Transition Time
Measured with a clock-like pattern at 2.5 Gbps,
between 20% and 80% of the differential output
voltage. de-emphasis disabled
Transition time is measured with fixture as shown in
Figure 5, adjusted to reflect the transition time at the
output pins
tPLH
Differential Low to High
Propagation Delay
Measured at 50% differential voltage from input to
output
tPHL
Differential High to Low
Propagation Delay
tSKP
Pulse Skew
tSKO
tSKPP
1
ns
1
ns
|tPHL–tPLH|
20
ps
Output Skew
(Note 7)
Difference in propagation delay between two outputs
in the same device
100
ps
Part-to-Part Skew
Difference in propagation delay between the same
output from devices operating under identical
conditions
100
ps
6
ns
2
2
2
psrms
psrms
psrms
35
Pspp
2.5
Gbps
tSM
Mux Switch Time
Measured from VIH or VIL of the mux-control or
loopback control to 50% of the valid differential output
RJ
Device Random Jitter
(Note 5)
See Figure 5 for test circuit.
Alternating-1-0 pattern
EQ and de-emphasis disabled.
At 0.25 Gbps
At 1.25 Gbps
At 2.5 Gbps
DJ
DR
1.8
Device Deterministic Jitter See Figure 5 for test circuit.
(Note 6)
EQ and de-emphasis disabled
Between 0.25 and 2.5 Gbps with PRBS7 pattern for
DS25MB100 @ –40°C to 85°C
Data Rate (Note 9)
Tested with alternating-1-0 pattern
0.25
Note 1: “Absolute Maximum Ratings” are the ratings beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the device
should be operated at these limits.
Note 2: Typical parameters measured at VCC = 3.3V, TA = 25°C, and represent most likely parametric norms at the time of product characterization. The typical
specifications are not guaranteed.
Note 3: IN+ and IN− are generic names refer to one of the many pairs of complimentary inputs of the DS25MB100. OUT+ and OUT− are generic names refer to
one of the many pairs of the complimentary outputs of the DS25MB100. Differential input voltage VID is defined as |IN+–IN−|. Differential output voltage VOD is
defined as |OUT+–OUT−|.
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8
K28.5 pattern is a 20-bit repeating pattern of +K28.5 and −K28.5 code groups {110000 0101 001111 1010}
Note 5: Device output random jitter is a measurement of the random jitter contribution from the device. It is derived by the equation sqrt(RJOUT2– RJIN2), where
RJOUT is the total random jitter measured at the output of the device in psrms, RJIN is the random jitter of the pattern generator driving the device.
Note 6: Device output deterministic jitter is a measurement of the deterministic jitter contribution from the device. It is derived by the equation (DJOUT–DJIN), where
DJOUT is the total peak-to-peak deterministic jitter measured at the output of the device in pspp, DJIN is the peak-to-peak deterministic jitter of the pattern generator
driving the device.
Note 7: tSKO is the magnitude difference in the propagation delays among data paths between switch A and switch B of the same port and similar data paths
between port 0 and port 1. An example is the output skew among data paths from SIA_0± to LO_0±, SIB_0± to LO_0±, SIA_1± to LO_1± and SIB_1± to LO_1
±. Another example is the output skew among data paths from LI_0± to SOA_0±, LI_0± to SOB_0±, LI_1± to SOA_1± and LI_1± to SOB_1±. tSKO also refers to
the delay skew of the loopback paths of the same port and between similar data paths between port 0 and port 1. An example is the output skew among data
paths SIA_0± to SOA_0±, SIB_0± to SOB_0±, SIA_1± to SOA_1± and SIB_1± to SOB_1±.
Note 8: Thermal resistances are based on having 16 thermal relief vias on the DAP pad under the 0 airflow condition.
Note 9: This parameter is guaranteed by design and/or characterization. It is not tested in production.
Note 10: ESD tests conform to the following standards:
Human Body Model applicable standard: MIL-STD-883, Method 3015.7
Machine Model applicable standard: JESD22-A115-A (ESD MM standard of JEDEC)
Field-induced Charge Device Model: Applicable standard JESD22-C101-C (ESD FICDM standard of JEDEC)
9
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DS25MB100
Note 4: K28.7 pattern is a 10-bit repeating pattern of K28.7 code group {001111 1000}
DS25MB100
Timing Diagrams
20208905
FIGURE 2. Driver Output Transition Time
20208906
FIGURE 3. Propagation Delay from Input to Output
20208907
FIGURE 4. Test Condition for Output Pre-Emphasis Duration
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10
DS25MB100
20208908
FIGURE 5. AC Test Circuit
11
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DS25MB100
Application Information
20208909
FIGURE 6. Application Diagram
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12
DS25MB100
20208910
FIGURE 7. Chassis Based Network Switch System With Redundancy
13
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DS25MB100
Physical Dimensions inches (millimeters) unless otherwise noted
LLP-36 Package
Order Number DS25MB100TSQ
NS Package Number SQA36A
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14
DS25MB100
Notes
15
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DS25MB100 2.5 Gb/s 1:2 Mux/Buffer with Input Equalization and Output De-Emphasis
Notes
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