DS25MB200
Dual 2.5 Gbps 2:1/1:2 CML Mux/Buffer with Transmit PreEmphasis and Receive Equalization
General Description
Features
The DS25MB200 is a dual signal conditioning 2:1 multiplexer
and 1:2 fan-out buffer designed for use in backplane redundancy applications. Signal conditioning features include input
equalization and programmable output pre-emphasis that enable data communication in FR4 backplanes up to 2.5 Gbps.
Each input stage has a fixed equalizer to reduce ISI distortion
from board traces. All output drivers have 4 selectable steps
of pre-emphasis to compensate for transmission losses from
long FR4 backplanes and reduce deterministic jitter. The preemphasis levels can be independently controlled for the lineside and switch-side drivers. The internal loopback paths from
switch-side input to switch-side output enable at-speed system testing. All receiver inputs are internally terminated with
100Ω differential terminating resistors. All drivers are internally terminated with 50Ω to VCC.
■
■
■
■
■
■
■
■
■
0.6–2.5 Gbps low jitter operation
Fixed input equalization
Programmable output pre-emphasis
Independent switch and line side pre-emphasis controls
Programmable switch-side loopback modes
On-chip terminations
HBM ESD rating 6 kV on all pins
+3.3V supply
Lead-less LLP-48 package (7mm x 7mm x 0.8mm, 0.5mm
pitch)
■ —40°C to +85°C operating temperature range
Applications
■ Backplane or cable driver
■ Redundancy and signal conditioning applications
Functional Block Diagram
20182333
© 2008 National Semiconductor Corporation
201823
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DS25MB200 Dual 2.5 Gbps 2:1/1:2 CML Mux/Buffer with Transmit Pre-Emphasis and Receive
Equalization
April 9, 2008
DS25MB200
Simplified Block Diagram
20182331
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2
DS25MB200
Connection Diagram
20182332
Order Number DS25MB200TSQ
See NS Package Number NSQAV48
3
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DS25MB200
Pin Descriptions
Pin Name
Pin Number
I/O
Description
LINE SIDE HIGH SPEED DIFFERENTIAL IO's
LI_0+
LI_0−
6
7
I
Inverting and non-inverting differential inputs of port_0 at the line side. LI_0+ and LI_0− have an
internal 50Ω connected to an internal reference voltage. See Figure 6.
LO_0+
LO_0−
33
34
O
Inverting and non-inverting differential outputs of port_0 at the line side. LO_0+ and LO_0− have
an internal 50Ω connected to VCC.
LI_1+
LI_1−
30
31
I
Inverting and non-inverting differential inputs of port_1 at the line side. LI_1+ and LI_1− have an
internal 50Ω connected to an internal reference voltage. See Figure 6.
LO_1+
LO_1−
9
10
O
Inverting and non-inverting differential outputs of port_1 at the line side. LO_1+ and LO_1− have
an internal 50Ω connected to VCC.
SWITCH SIDE HIGH SPEED DIFFERENTIAL IO's
SOA_0+
SOA_0−
46
45
O
Inverting and non-inverting differential outputs of mux_0 at the switch_A side. SOA_0+ and SOA_0
− have an internal 50Ω connected to VCC.
SOB_0+
SOB_0−
4
3
O
Inverting and non-inverting differential outputs of mux_0 at the switch_B side. SOB_0+ and SOB_0
− have an internal 50Ω connected to VCC.
SIA_0+
SIA_0−
40
39
I
Inverting and non-inverting differential inputs to the mux_0 at the switch_A side. SIA_0+ and SIA_0
− have an internal 50Ω connected to an internal reference voltage. See Figure 6.
SIB_0+
SIB_0−
43
42
I
Inverting and non-inverting differential inputs to the mux_0 at the switch_B side. SIB_0+ and SIB_0
− have an internal 50Ω connected to an internal reference voltage. See Figure 6.
SOA_1+
SOA_1−
22
21
O
Inverting and non-inverting differential outputs of mux_1 at the switch_A side. SOA_1+ and SOA_1
− have an internal 50Ω connected to VCC.
SOB_1+
SOB_1−
28
27
O
Inverting and non-inverting differential outputs of mux_1 at the switch_B side. SOB_1+ and SOB_1
− have an internal 50Ω connected to VCC.
SIA_1+
SIA_1−
16
15
I
Inverting and non-inverting differential inputs to the mux_1 at the switch_A side. SIA_1+ and SIA_1
− have an internal 50Ω connected to an internal reference voltage. See Figure 6.
SIB_1+
SIB_1−
19
18
I
Inverting and non-inverting differential inputs to the mux_1 at the switch_B side. SIB_1+ and SIB_1
− have an internal 50Ω connected to an internal reference voltage. See Figure 6.
CONTROL (3.3V LVCMOS)
MUX_S0
37
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.
MUX_S1
13
I
A logic low at MUX_S1 selects mux_1 to switch B. MUX_S0 is internally pulled high. Default state
for mux_1 is switch A.
PREL_0
PREL_1
12
1
I
PREL_0 and PREL_1 select the output pre-emphasis of the line side drivers (LO_0± and LO_1±).
PREL_0 and PREL_1 are internally pulled high. See Table 3 for line side pre-emphasis levels.
PRES_0
PRES_1
36
25
I
PRES_0 and PRES_1 select the output pre-emphasis of the switch side drivers (SOA_0±, SOB_0
±, SOA_1± and SOB_1±). PRES_0 and PRES_1 are internally pulled high. See Table 4 for switch
side pre-emphasis levels.
LB0A
47
I
A logic low at LB0A enables the internal loopback path from SIA_0± to SOA_0±. LB0A is internally
pulled high.
LB0B
48
I
A logic low at LB0B enables the internal loopback path from SIB_0± to SOB_0±. LB0B is internally
pulled high.
LB1A
23
I
A logic low at LB1A enables the internal loopback path from SIA_1± to SOA_1±. LB1A is internally
pulled high.
LB1B
24
I
A logic low at LB1B enables the internal loopback path from SIB_1± to SOB_1±. LB1B is internally
pulled high.
RSV
26
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.
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4
Pin Number
I/O
Description
2, 8, 14, 20,
29, 35, 38,
44
P
VCC = 3.3V ± 5%.
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.
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
5, 11, 17, 32,
41
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
Die Attach Pad (DAP) is the metal contact at the bottom side, located at the center of the LLP-48
package. It should be connected to the GND plane with at least 4 via to lower the ground impedance
and improve the thermal performance of the package.
parity. The DS25MB200 provides 4 steps of user-selectable
pre-emphasis ranging from 0, −3, −6 and –9 dB to handle
different lengths of backplane. Figure 1 shows a driver preemphasis waveform. The pre-emphasis duration is 188 ps
nominal, corresponds to 0.47 bit-width at 2.5 Gbps. The preemphasis levels of switch-side and line-side can be individually programmed.
The high speed inputs are self-biased to about 1.5V and are
designed for AC coupling. The inputs are compatible to most
AC coupling differential signals such as LVDS, LVPECL and
CML. See Figure 6 for details.
Functional Description
The DS25MB200 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 pre-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 dis-
TABLE 1. LOGIC TABLE FOR MULTIPLEX CONTROLS
MUX_S0
Mux Function
0
MUX_0 select switch_B input, SIB_0±.
1 (default)
MUX_0 select switch_A input, SIA_0±.
MUX_S1
Mux Function
0
MUX_1 select switch_B input, SIB_1±.
1 (default)
MUX_1 select switch_A input, SIA_0±.
TABLE 2. LOGIC TABLE FOR LOOPBACK CONTROLS
LB0A
Loopback Function
0
Enable loopback from SIA_0± to SOA_0±.
1 (default)
Normal mode. Loopback disabled.
LB0B
Loopback Function
0
Enable loopback from SIB_0± to SOB_0±.
1 (default)
Normal mode. Loopback disabled.
LB1A
Loopback Function
0
Enable loopback from SIA_1± to SOA_1±.
1 (default)
Normal mode. Loopback disabled.
LB1B
Loopback Function
0
Enable loopback from SIB_1± to SOB_1±.
1 (default)
Normal mode. Loopback disabled.
5
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DS25MB200
Pin Name
DS25MB200
TABLE 3. LINE-SIDE PRE-EMPHASIS CONTROLS
PreL_[1:0]
Pre-Emphasis Level in
mVPP
(VODB)
De-Emphasis Level
in mVPP
(VODPE)
00
1200
1200
0
10 inches
01
1200
849.53
−3
20 inches
10
1200
600
−6
30 inches
1 1 (default)
1200
425.78
−9
40 inches
Pre-Emphasis in dB
(VODPE/VODB)
Typical FR4 board
trace
TABLE 4. SWITCH-SIDE PRE-EMPHASIS CONTROLS
PreS_[1:0]
Pre-Emphasis Level in
mVPP
(VODB)
De-Emphasis Level
in mVPP
(VODPE)
Pre-Emphasis in dB
(VODPE/VODB)
00
1200
1200
0
10 inches
01
1200
849.53
−3
20 inches
10
1200
600
−6
30 inches
1 1 (default)
1200
425.78
−9
40 inches
Typical FR4 board
trace
20182337
FIGURE 1. Driver Pre-Emphasis Differential Waveform (showing all 4 pre-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 sec
Thermal Resistance, θJC-top
20.7°C/W
6 kV
Recommended Operating Ratings
Min
Supply Voltage (VCC-GND)
Typ
Max
Units
3.135 3.3
3.465
V
50
mVPP
85
°C
100
°C
Supply Noise Amplitude
10 Hz to 2 GHz
Ambient Temperature
+260°C
33.7°C/W
18.2°C/W
ESD Rating HBM, 1.5 kΩ, 100 pF
−0.3V to 4V
−0.3V to (VCC +0.3V)
−0.3V to (VCC +0.3V)
+150°C
−65°C to +150°C
Thermal Resistance, θJA
5.8°C/W
Thermal Resistance, ΦJB
–40
Case Temperature
Electrical Characteristics
Over recommended operating supply and temperature ranges unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ
(Note 2)
Max
Units
LVCMOS DC SPECIFICATIONS
VIH
High Level Input
Voltage
2.0
VCC +0.3
V
VIL
Low Level Input
Voltage
−0.3
0.8
V
IIH
High Level Input
Current
VIN = VCC
−10
10
µA
IIL
Low Level Input
Current
VIN = GND
75
124
µA
RPU
Pull-High Resistance
94
35
kΩ
RECEIVER SPECIFICATIONS
VID
Differential Input
Voltage Range
AC Coupled Differential Signal
Below 1.25 Gbps
Above 1.25 Gbps
Measured at input pins.
VICM
Common Mode
Voltage at Receiver
Inputs
Measured at receiver inputs reference to ground.
Input Differential
Termination
On-chip differential termination between IN+ or IN
−.
RITD
100
100
1750
1560
1.5
mVP-P
mVP-P
V
84
100
116
Ω
1000
1200
1400
mVP-P
0
−3
−6
−9
dB
dB
dB
dB
DRIVER SPECIFICATIONS
VODB
VPE
Output Differential
Voltage Swing without
Pre-Emphasis
RL = 100Ω ±1%
PRES_1=PRES_0=0
PREL_1=PREL_0=0
Driver pre-emphasis disabled.
Running K28.7 pattern at 2.5 Gbps.
See Figure 5 for test circuit.
Output Pre-Emphasis RL = 100Ω ±1%
Voltage Ratio
Running K28.7 pattern at 2.5 Gbps
20*log(VODPE/VODB) PREx_[1:0]=00
PREx_[1:0]=01
PREx_[1:0]=10
PREx_[1:0]=11
x=S for switch side pre-emphasis control
x=L for line side pre-emphasis control
See Figure 1 on waveform.
See Figure 5 for test circuit.
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DS25MB200
Thermal Resistance, θJC-bottom
Absolute Maximum Ratings (Note 1)
DS25MB200
Symbol
tPE
Conditions
Min
Typ
(Note 2)
Max
Units
Tested at −9 dB pre-emphasis level, PREx[1:0]=11
x=S for switch side pre-emphasis control
x=L for line side pre-emphasis control
See Figure 4 on measurement condition.
125
188
400
ps
42
50
58
Ω
Parameter
Pre-Emphasis Width
ROTSE
Output Termination
On-chip termination from OUT+ or OUT− to VCC
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
Ω
100
2.4
5
%
2.9
V
1
W
POWER DISSIPATION
PD
Power Dissipation
VDD = 3.465V
All outputs terminated by 100Ω ±1%.
PREL_[1:0]=0, PRES_[1:0]=0
Running PRBS 27-1 pattern at 2.5 Gbps
AC CHARACTERISTICS
tR
tF
Differential Low to High Measured with a clock-like pattern at 100 MHz,
Transition Time
between 20% and 80% of the differential output
Differential High to Low voltage. Pre-emphasis disabled.
Transition time is measured with fixture as shown
Transition Time
in Figure 5, adjusted to reflect the transition time at
the output pins.
80
ps
80
ps
tPLH
Differential Low to High Measured at 50% differential voltage from input to
Propagation Delay
output.
0.5
2
ns
tPHL
Differential High to Low
Propagation Delay
0.5
2
ns
tSKP
Pulse Skew
|tPHL–tPLH|
20
ps
tSKO
Output Skew
(Note 7)
Difference in propagation delay between two
outputs in the same device.
200
ps
tSKPP
Part-to-Part Skew
Difference in propagation delay between the same
output from devices operating under identical
conditions.
500
ps
6
ns
2
2
psrms
psrms
tSM
RJ
Mux Switch Time
Device Random Jitter
(Note 5)
Measured from VIH or VIL of the mux-control or
loopback control to 50% of the valid differential
output.
See Figure 5 for test circuit.
Alternating-1-0 pattern.
Pre-emphasis disabled.
At 1.25 Gbps
At 2.5 Gbps
DJ
Device Deterministic
Jitter (Note 6)
See Figure 5 for test circuit.
Pre-emphasis disabled.
Between 0.8 and 2.5 Gbps with PRBS7 pattern for
DS25MB200 @ –40°C to 85°C
DRMAX
Maximum Data Rate
DRMIN
Minimum Data Rate
Tested with alternating 1-0 pattern
(Note 8)
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1.8
8
30
2.5
Pspp
Gbps
0.6
Gbps
Note 2: Typical parameters measured at VCC = 3.3V, TA = 25°C. They are for reference purposes and are not production-tested.
Note 3: IN+ and IN− are generic names refer to one of the many pairs of complimentary inputs of the DS25MB200. OUT+ and OUT− are generic names refer to
one of the many pairs of the complimentary outputs of the DS25MB200. Differential input voltage VID is defined as |IN+–IN−|. Differential output voltage VOD is
defined as |OUT+–OUT−|.
Note 4: K28.7 pattern is a 10-bit repeating pattern of K28.7 code group {001111 1000}
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 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 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: For operation under 1 Gbps, encoded data transmission is recommended (i.e. 8b10b).
Timing Diagrams
20182336
FIGURE 2. Driver Output Transition Time
20182335
FIGURE 3. Propagation Delay from Input to Output
9
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DS25MB200
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.
DS25MB200
20182339
FIGURE 4. Test Condition for Output Pre-Emphasis Duration
20182334
FIGURE 5. AC Test Circuit
20182350
FIGURE 6. Receiver Input Termination and Biasing Circuit
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10
The DS25MB200 input equalizer provides equalization to
compensate about 5 dB of transmission loss from a short
backplane transmission line. For characterization purposes,
a 25-inch FR4 coupled micro-strip board trace is used in place
Trace Length
Finished Trace
Width W
25 inches
8.5 mil
Dielectric Constant
Separation between
Dielectric Height H
Traces
εR
11.5 mil
6 mil
3.8
Loss Tangent
0.022
20182344
FIGURE 7. Application Diagram (showing data paths of port 0)
11
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DS25MB200
of the short backplane link. The 25-inch microstrip board trace
has approximately 5 dB of attenuation between 375 MHz and
1.875 GHz, representing closely the transmission loss of the
short backplane transmission line. The 25-inch microstrip is
connected between the pattern generator and the differential
inputs of the DS25MB200 for AC measurements.
Application Information
DS25MB200
Physical Dimensions inches (millimeters) unless otherwise noted
LLP-48 Package
Order Number DS25MB200TSQ
NS Package Number NSQAV48
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DS25MB200
Notes
13
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DS25MB200 Dual 2.5 Gbps 2:1/1:2 CML Mux/Buffer with Transmit Pre-Emphasis and Receive
Equalization
Notes
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