19-0770; Rev 0; 4/07
5.0Gbps PCI Express Passive Switches
/MX489A
General Description
Features
The MAX4888A/MAX4889A high-speed passive switches
route PCI Express® (PCIe) data between two possible
destinations. The MAX4888A is a quad single-pole/dou-
ble-throw (4 x SPDT) switch ideally suited for switching
two half lanes of PCIe data between two destinations. The
MAX4889A is an octal single-pole/double-throw (8 x
SPDT) switch ideal for switching four half lanes of PCIe
data between four destinations. The MAX4888A/
MAX4889A feature a single digital control input (SEL) to
switch signal paths.
o Single 1.65V to 3.6V Power-Supply Voltage
o Low Same-Pair Skew of 7ps
o Low 120µA (Max) Quiescent Current
o Supports PCIe Gen I and Gen || Data Rates
o Flow-Through Pin Configuration for Ease of
Layout
o Industry-Compatible Pinout
o Lead-Free Packaging
The MAX4888A/MAX4889A are fully specified to oper-
ate from a single 3.0V to 3.6V power supply and also
operate down to +1.65V. The MAX4888A is available
in a 3.5mm x 5.5mm, 28-pin TQFN package. The
MAX4889A is available in a 3.5mm x 9.0mm, 42-pin
TQFN package. Both devices operate over the -40°C to
+85°C temperature range.
Ordering Information/
Selector Guide
PIN-
PACKAGE
PKG
CODE
PART
CONFIGURATION
Applications
Two
Half Lanes
Desktop Computers
Servers/Storage Area Networks
Laptops
MAX4888AETI+ 28 TQFN-EP*
T283555-1
Four Half
Lanes
MAX4889AETO+ 42 TQFN-EP*
T423590M-1
Note: All devices are specified over the -40°C to +85°C operat-
ing temperature range.
+Denotes lead-free package.
*EP = Exposed paddle.
PCI Express is a registered trademark of PCI-Sig Corp.
Typical Application Circuit appears at end of data sheet.
Pin Configurations
TOP VIEW
38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22
24 23 22 21 20 19 18 17 16 15
39
40
21 GND
20 V+
25
26
14 GND
13 V+
GND
V+
GND
V+
MAX4888A
GND 41
V+ 42
MAX4889A
19 GND
18 V+
GND 27
V+ 28
12 GND
11 V+
*EP
*EP
+
+
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17
1
2
3
4
5
6
7
8
9
10
TQFN
TQFN
*CONNECT EXPOSED PADDLE TO GROUND.
________________________________________________________________ Maxim Integrated Products
1
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5.0Gbps PCI Express Passive Switches
/MX489A
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 3.0V to 3.6V, T = -40°C to +85°C, unless otherwise noted. Typical values are at V+ = 3.3V, T = +25°C.) (Note 2)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DYNAMIC
Turn-On Time
t
V
V
or V
or V
= 1.0V, R = 50Ω, Figure 1
90
10
50
250
50
ns
ns
ps
ON
NO_
NO_
NC_
NC_
L
Turn-Off Time
t
= 1.0V, R = 50Ω, Figure 1
OFF
L
Propagation Delay
t
R = R = 50Ω, unbalanced, Figure 2
PD
S
L
R = R = 50Ω, unbalanced; skew between
any two pairs, Figure 2
S
L
Output Skew Between Pairs
t
t
50
10
ps
ps
SK1
SK2
Output Skew Between Same
Pair
R = R = 50Ω, unbalanced; skew between
S
L
two lines on same pair, Figure 2
R = R = 50Ω,
unbalanced,
Figure 3
S
L
1MHz < f < 100MHz
-0.5
-1.4
On-Loss
G
dB
dB
LOS
CT1
500MHz< f < 1.25GHz
Crosstalk between
any two pairs,
f = 50MHz
-53
-32
Crosstalk
V
R = R = 50Ω,
S
L
unbalanced,
Figure 3
f = 1.25GHz
Signaling Data Rate
Off-Isolation
BR
R = R = 50Ω
5.0
-56
Gbps
dB
S
L
Signal = 0dBm,
f = 10MHz
V
R = R = 50Ω,
ISO
S
L
f = 1.25GHz
-26
Figure 3
C
NO_/NC_(OFF)
NO_/NC_ Off-Capacitance
COM_ On-Capacitance
LOGIC INPUT
Figure 4
Figure 4
1
2
pF
pF
C
COM_(ON)
Input-Logic Low
V
0.5
+1
V
V
IL
Input-Logic High
V
1.4
-1
IH
Input-Logic Hysteresis
Input Leakage Current
POWER SUPPLY
V
100
mV
µA
HYST
I
V
V
= 0V or V+
= 0V or V+
IN
SEL
SEL
Power-Supply Range
V+
I+
1.65
3.60
60
V
MAX4888A
MAX4889A
V+ Supply Current
µA
120
Note 2: All units are 100% production tested at T = +85°C. Limits over the operating temperature range are guaranteed by design
A
and characterization and are not production tested.
Note 3: ΔR
= R
- R
.
ON
ON (MAX)
ON (MIN)
Note 4: Guaranteed by design. Not production tested.
Note 5: Flatness is defined as the difference between the maximum and minimum value of on-resistance as measured over the
specified analog signal range.
_______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
ON-RESISTANCE vs. V
(V+ = 1.8V)
ON-RESISTANCE vs. V
(V+ = 2.5V)
COM
COM
ON-RESISTANCE vs. V
COM
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
14
12
10
8
14
12
10
8
T
= +85°C
T
= +85°C
A
A
V+ = 1.8V
T
= +25°C
A
T
= +25°C
A
V+ = 2.5V
6
6
T
= -40°C
A
4
4
V+ = 3.3V
2
2
T
= -40°C
A
0
0
-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1
(V)
-0.1
0
0.1 0.2 0.3 0.4 0.5 0.6
(V)
-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3
(V)
V
V
V
COM
COM
COM
ON-RESISTANCE vs. V
(V+ = 3.3V)
COM
SUPPLY CURRENT vs. TEMPERATURE
(MAX4889A)
/MX489A
LOGIC THRESHOLD vs. SUPPLY VOLTAGE
14
12
10
8
80
70
60
50
40
30
20
10
0
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
T
= +85°C
A
T
= +25°C
A
V
IH
V+ = 3.3V
V+ = 2.5V
6
V
IL
4
2
V+ = 1.8V
T
= -40°C
A
0
-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1
(V)
-40
-15
10
35
60
85
1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
SUPPLY VOLTAGE (V)
V
TEMPERATURE (°C)
COM
TURN-ON/-OFF TIME vs. SUPPLY VOLTAGE
240
220
200
180
160
140
120
100
80
NO_ t
ON
NC_ t
ON
60
NO_ t
OFF
40
NC_ t
OFF
20
0
1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
/MX489A
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
EYE DIAGRAM
(V+ = 3.3V, f = 1.25GHz,
EYE DIAGRAM
(V+ = 2.5V, f = 1.25GHz,
EYE DIAGRAM
(V+ = 1.8V, f = 1.25GHz,
†
†
†
600mV PRBS SIGNAL, R = R = 50Ω)
600mV PRBS SIGNAL, R = R = 50Ω)
600mV PRBS SIGNAL, R = R = 50Ω)
P-P
S
L
P-P
S
L
P-P
S
L
V
V
V
COM_+
COM_+
COM_+
50mV/div
50mV/div
50mV/div
V
V
V
COM_-
COM_-
COM_-
50ps/div
50ps/div
50ps/div
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 1, 2.5Gbps; U1 = 400ps
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 1, 2.5Gbps; U1 = 400ps
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 1, 2.5Gbps; U1 = 400ps
†
†
†
EYE DIAGRAM
(V+ = 1.8V, f = 2.5GHz,
EYE DIAGRAM
(V+ = 2.5V, f = 2.5GHz,
EYE DIAGRAM
(V+ = 3.3V, f = 2.5GHz,
††
††
††
600mV PRBS SIGNAL, R = R = 50Ω)
600mV PRBS SIGNAL, R = R = 50Ω)
600mV PRBS SIGNAL, R = R = 50Ω)
P-P
S
L
P-P
S
L
P-P
S
L
V
V
V
COM_+
COM_+
COM_+
50mV/div
50mV/div
50mV/div
V
V
V
COM_-
COM_-
COM_-
25ps/div
25ps/div
25ps/div
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 11, 5.0Gbps; U1 = 200ps
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 11, 5.0Gbps; U1 = 200ps
*PRBS = PSEUDORANDOM BIT SEQUENCE
= GEN 11, 5.0Gbps; U1 = 200ps
††
††
††
_______________________________________________________________________________________
5
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5.0Gbps PCI Express Passive Switches
Pin Description
PIN
NAME
FUNCTION
MAX4888A
MAX4889A
1, 10, 12, 14, 1, 4, 10, 14, 17,
GND
Ground
20, 25, 27
19, 21, 39, 41
2
3, 9
4
5
6
9
—
2
3
6
SEL
N.C.
COM1+
COM1-
COM2+
COM2-
Digital Control Input
No Connection. Not internally connected.
Analog Switch 1. Common Positive Terminal.
Analog Switch 1. Common Negative Terminal.
Analog Switch 2. Common Positive Terminal.
Analog Switch 2. Common Negative Terminal.
7
7
5, 8, 13, 18,
20, 30,
Positive-Supply Voltage Input. Connect V+ to a 1.65V to 3.6V supply voltage.
Bypass V+ to GND with a 0.1µF capacitor placed as close to the device as possible
(See the Board Layout section).
8, 11, 13, 19,
26, 28
V+
40, 42
15
16
17
18
21
22
23
24
—
—
—
—
—
—
—
—
—
—
—
—
EP
31
32
33
34
35
36
37
38
11
12
15
16
22
23
24
25
26
27
28
29
EP
NO2-
NO2+
NO1-
Analog Switch 2. Normally Open Negative Terminal.
Analog Switch 2. Normally Open Positive Terminal.
Analog Switch 1. Normally Open Negative Terminal.
Analog Switch 1. Normally Open Positive Terminal.
Analog Switch 2. Normally Closed Negative Terminal.
Analog Switch 2. Normally Closed Positive Terminal.
Analog Switch 1. Normally Closed Negative Terminal.
Analog Switch 1. Normally Closed Positive Terminal.
Analog Switch 3. Common Positive Terminal.
NO1+
NC2-
/MX489A
NC2+
NC1-
NC1+
COM3+
COM3-
COM4+
COM4-
NO4-
Analog Switch 3. Common Negative Terminal.
Analog Switch 4. Common Positive Terminal.
Analog Switch 4. Common Negative Terminal.
Analog Switch 4. Normally Open Negative Terminal.
Analog Switch 4. Normally Open Positive Terminal.
Analog Switch 3. Normally Open Negative Terminal.
Analog Switch 3. Normally Open Positive Terminal.
Analog Switch 4. Normally Closed Negative Terminal.
Analog Switch 4. Normally Closed Positive Terminal.
Analog Switch 3. Normally Closed Negative Terminal.
Analog Switch 3. Normally Closed Positive Terminal.
Exposed Paddle. Connect EP to GND.
NO4+
NO3-
NO3+
NC4-
NC4+
NC3-
NC3+
EP
6
_______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
/MX489A
Test Circuits/Timing Diagrams
MAX4888A/MAX4889A
3.3V
V+
t
t
< 5ns
< 5ns
r
f
V
IH
LOGIC
INPUT
50%
V
IL
NO_
COM_
V
N_
V
OUT
OR NC_
t
OFF
R
L
C
L
SEL
V
OUT
0.9 x V
0.9 x V
OUT
0UT
GND
LOGIC
INPUT
SWITCH
OUTPUT
0V
t
ON
C
V
INCLUDES FIXTURE AND STRAY CAPACITANCE.
L
R
L
= V
N_
OUT
(
)
ON
R
L
+ R
V
N_
= V OR V
NO_ NC_
Figure 1. Switching Time
_______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
Test Circuits/Timing Diagrams (continued)
3.3V
V+
MAX4888A/MAX4889A
NO_+ OR
NC_+
R
R
S
COM
COM
_+
IN+
IN-
OUT+
OUT-
RISE-TIME PROPAGATION DELAY = t
OR t
PLHY
PLHX
FALL-TIME PROPAGATION DELAY = t
OR t
PHLY
PHLX
R
R
L
t
=
DIFFERENCE IN PROPAGATION DELAY (RISE-FALL)
BETWEEN ANY TWO PAIRS
SK1
SK2
NO_- OR
NC_-
S
_-
t
= | t - t | OR | t
- t
PHLX PLHY
|
PLHX PHLY
BETWEEN TWO LINES ON THE SAME PAIR
L
SEL
/MX489A
t
INFALL
t
INRISE
10%
1.5V
90%
90%
V
IN+
50%
50%
50%
10%
0V
1.5V
V
50%
IN-
0V
t
t
OUTRISE
OUTFALL
10%
t
t
PLHX
PHLX
1.5V
90%
90%
V
OUT+
50%
50%
10%
0V
1.5V
50%
50%
V
OUT-
0V
t
t
PHLY
PLHY
Figure 2. Propagation Delay and Output Skew
8
_______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
/MX489A
Test Circuits/Timing Diagrams (continued)
0.1μF
3.3V
V+
V
V
OUT
OFF-ISOLATION = 20log
ON-LOSS = 20log
IN
NETWORK
ANALYZER
V
50Ω
50Ω
OUT
V
V
0V OR V+
IN
SEL
V
IN
COM_
V
OUT
MAX4888A/MAX4889A
CROSSTALK = 20log
NC_
V
IN
MEAS
REF
OUT
NO_
50Ω
50Ω
50Ω
GND
MEASUREMENTS ARE STANDARDIZED AGAINST SHORTS AT IC TERMINALS.
OFF-ISOLATION IS MEASURED BETWEEN COM_ AND "OFF" NO_ OR NC_ TERMINAL ON EACH SWITCH.
ON-LOSS IS MEASURED BETWEEN COM_ AND "ON" NO_ OR NC_ TERMINAL ON EACH SWITCH.
CROSSTALK IS MEASURED BETWEEN ANY TWO PAIRS.
SIGNAL DIRECTION THROUGH SWITCH IS REVERSED; WORST VALUES ARE RECORDED.
Figure 3. On-Loss, Off-Isolation, and Crosstalk
two sets of eight lanes from a single 16-lane bus. The
MAX4888A/MAX4889A feature a single digital control
input (SEL) to switch signal paths.
3.3V
0.1μF
The MAX4888A/MAX4889A are fully specified to oper-
ate from a single 3.0V to 3.6V power supply and also
operate down to 1.65V.
V+
COM_
MAX4888A/MAX4889A
SEL
Digital Control Input (SEL)
The MAX4888A/MAX4889A provide a single digital
control input (SEL) to select the signal path between
the COM__ and NO__/NC__ channels. The truth tables
for the MAX4888A/MAX4889A are depicted in the
Functional Diagrams/Truth Table section. Drive SEL
rail-to-rail to minimize power consumption.
V
IL
OR V
IH
CAPACITANCE
METER
NC_ or
NO_
GND
Analog Signal Levels
The MAX4888A/MAX4889A accept standard PCIe sig-
nals to a maximum of V+ - 1.2V. Signals on the COM_+
channels are routed to either the NO_+ or NC_+ chan-
nels, and signals on the COM_- channels are routed to
either the NO_- or NC_- channels. The MAX4888A/
MAX4889A are bidirectional switches, allowing COM__,
NO__, and NC__ to be used as either inputs or outputs.
Figure 4. Channel Off-/On-Capacitance
Detailed Description
The MAX4888A/MAX4889A high-speed passive switch-
es route PCIe data between two possible destinations.
The MAX4888A/MAX4889A are ideal for routing PCIe sig-
nals to change the system configuration. For example, in
a graphics application, the MAX4888A/MAX4889A create
_______________________________________________________________________________________
9
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5.0Gbps PCI Express Passive Switches
Functional Diagrams/Truth Table
V+
V+
MAX4888A
MAX4889A
COM1+
COM1-
NC1+
NC1-
NO1+
NO1-
NC2+
NC2-
NO2+
NO2-
COM1+
COM1-
NC1+
NC1-
NO1+
NO1-
NC2+
NC2-
NO2+
NO2-
NC3+
NC3-
NO3+
NO3-
NC4+
NC4-
NO4+
NO4-
COM2+
COM2-
COM2+
COM2-
/MX489A
SEL
COM3+
COM3-
GND
COM__TO COM__TO
NC__
COM4+
COM4-
SEL
NO__
0
1
ON
OFF
OFF
ON
SEL
GND
10 ______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
/MX489A
Applications Information
PCIe Switching
The MAX4888A/MAX4889A primary applications are
DATA
DIRECTION
aimed at reallocating PCIe lanes (see Figure 5). For
example, in graphics applications, several manufacturers
have found that it is possible to improve performance
by a factor of nearly two by splitting a single 16-lane
PCIe bus into two 8-lane buses. Two of the more promi-
nent examples are SLI™ (Scaled Link Interface) and
CrossFire™. The MAX4889A permits a computer
motherboard to operate properly with a single 16-lane
graphics card, and can later be updated to dual cards.
The same motherboard can be used with dual cards
where the user sets a jumper or a bit through software
to switch between single- or dual-card operation.
Common mode below 1V operation requirement.
MAX4888A
MAX4889A
ONE LANE
DATA IS ROUTED
TO EITHER
BOARD A OR B
NOTE: ONLY ONE LANE IS SHOWN FOR CLARITY
Board Layout
High-speed switches require proper layout and design
procedures for optimum performance. Keep design-
controlled impedance PCB traces as short as possible
or follow impedance layouts per the PCIe specification.
Ensure that power-supply bypass capacitors are
placed as close to the device as possible. Multiple
bypass capacitors are recommended. Connect all
grounds and the exposed pad to large ground planes.
Common mode below 1V operation requirement.
A
B
Figure 5. The MAX4888A/MAX4889A Used as a Single-Lane
Switch
Chip Information
PROCESS: CMOS
CrossFire is a trademark of ATI Technologies, Inc.
SLI is a trademark of NVIDIA Corporation.
______________________________________________________________________________________ 11
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5.0Gbps PCI Express Passive Switches
Typical Application Circuit
PCIe GRAPHICS INTERFACE
GRAPHICS
CARD 1
GRAPHICS
CARD 2
PCIe BUS
COM1+
COM1-
COM2+
COM2-
COM3+
COM3-
COM4+
COM4-
NC1+
LANE 0 TX
NC1-
NC2+
NC2-
NC3+
NC3-
NC4+
NC4-
NO1+
NO1-
NO2+
NO2-
NO3+
NO3-
NO4+
NO4-
LANE 1 TX
LANE 2 TX
LANE 3 TX
MAX4889A
/MX489A
SEL
CHANNEL SELECT
COM1+
COM1-
COM2+
COM2-
COM3+
COM3-
COM4+
COM4-
NC1+
NC1-
NC2+
NC2-
NC3+
NC3-
NC4+
NC4-
NO1+
NO1-
NO2+
NO2-
NO3+
NO3-
NO4+
NO4-
LANE 0 RX
LANE 1 RX
LANE 2 RX
LANE 3 RX
MAX4889A
SEL
CHANNEL SELECT
12 ______________________________________________________________________________________
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5.0Gbps PCI Express Passive Switches
/MX489A
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
°
______________________________________________________________________________________ 13
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5.0Gbps PCI Express Passive Switches
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
°
/MX489A
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products., Inc.
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