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19-0724; Rev 0; 5/07
2.5Gbps PCI Express Passive Switches
General Description
The MAX4888/MAX4889 high-speed passive switches route PCI Express(R) (PCIe) data between two possible destinations. The MAX4888 is a quad single-pole/doublethrow (4 x SPDT) switch ideally suited for switching two half lanes of PCIe data between two destinations. The MAX4889 is an octal single-pole/double-throw (8 x SPDT) switch ideal for switching four half lanes of PCIe data between four destinations. The MAX4888/MAX4889 feature a single digital control input (SEL) to switch signal paths. The MAX4888/MAX4889 are fully specified to operate from a single 3.0V to 3.6V power supply and also operate down to +1.65V. The MAX4888 is available in a 3.5mm x 5.5mm, 28-pin TQFN package. The MAX4889 is available in a 3.5mm x 9.0mm, 42-pin TQFN package. Both devices operate over the -40C to +85C temperature range. Low Same-Pair Skew of 7ps Low 120A (Max) Quiescent Current Supports PCIe Gen I Data Rates Flow-Through Pin Configuration for Ease of Layout Industry-Compatible Pinout Lead-Free Packaging
Features
Single 1.65V to 3.6V Power-Supply Voltage
MAX4888/MAX4889
Ordering Information/ Selector Guide
PART PINPACKAGE CONFIGURATION Two Half Lanes Four Half Lanes PKG CODE T283555-1 T423590M-1
Applications
Desktop Computers Servers/Storage Area Networks Laptops
MAX4888ETI+ 28 TQFN-EP* MAX4889ETO+ 42 TQFN-EP*
PCI Express is a registered trademark of PCI-Sig Corp.
Note: All devices are specified over the -40C to +85C operating temperature range. +Denotes lead-free package. *EP = Exposed paddle. Typical Application Circuit appears at end of data sheet.
Pin Configurations
TOP VIEW
NC1+ NC2+ NO1+ NO2+ NC3+ NC4+ NO3+ NO4+ COM4NC1NC2NO1NO2NC3NC4NO3NC1+ NC2+ NO1+ NO2+ NC1NC2NO1NO2GND NO421 GND 20 V+ 19 GND 18 V+ 3 COM14 GND 5 V+ 6 COM2+ 7 COM28 V+ 9 SEL 10 11 12 13 14 15 16 17 COM3+ V+ COM4+ GND COM3GND GND
V+
24 23 22 21 20 19 18 17 16 15 GND 25 V+ 26 GND 27 V+ 28 1 GND *EP + 2 SEL 3 N.C. 4 COM1+ 5 COM16 COM2+ 7 COM28 V+ 9 N.C. 10 GND 14 GND 13 V+ GND 39 V+ 40 GND 41 V+ 42
38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22
MAX4888
12 GND 11 V+
MAX4889
*EP + 1 GND 2 COM1+
TQFN
*CONNECT EXPOSED PADDLE TO GROUND.
TQFN
________________________________________________________________ Maxim Integrated Products
V+
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.) V+ .............................................................................-0.3V to +4V SEL, COM__, NO__, NC__ (Note 1) .............-0.3V to (V+ + 0.3V) | COM__ - NO__ |, | COM__ - NC__ | (Note 1) ...................0 to 2V Continuous Current (COM_ to NO__/NC__) .....................70mA Peak Current (COM__ to NO__/NC__) (pulsed at 1ms, 10% duty cycle)..................................70mA Continuous Current (SEL).................................................30mA Peak Current (SEL) (pulsed at 1ms, 10% duty cycle)................................150mA Continuous Power Dissipation (TA = +70C) 28-Pin TQFN (derate 20.8mW/C above +70C) ....1666.7mW 42-Pin TQFN (derate 35.7mW/C above +70C) ....2857.1mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Junction Temperature ......................................................+150C
Note 1: Signals on SEL, NO__, NC__ or COM__ exceeding V+ or GND are clamped by internal diodes. Limit forward-diode current to maximum current rating.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V+ = 3.0V to 3.6V, TA = -40C to +85C, unless otherwise noted. Typical values are at V+ = 3.3V, TA = +25C.) (Note 2)
PARAMETER ANALOG SWITCH Analog-Signal Range VCOM_, VNO_, VNC_ | VCOM_ VNO_ | , | VCOM_ VNC_ | RON RON RON RFLAT(ON) INO_(OFF) INC_(OFF) ICOM_(ON) V+ = 3.0V, ICOM_ = 15mA, VNO_ or VNC_ = 0V, 1.8V V+ = 3.0V, ICOM_ = 15mA, VNO_ or VNC_ = 0V (Notes 3, 4) V+ = 3.0V, ICOM_ = 15mA, VNO_ or VNC_ = 0V (Notes 3, 4) V+ = 3.0V, ICOM_ = 15mA VNO_ or VNC_ = 0V, 1.8V (Notes 4, 5) V+ = 3.6V; VCOM_ = 0V, 1.8V; VNO_ or VNC_ = 1.8V, 0V V+ = 3.6V; VCOM_ = 0V, 1.8V; VNO_ or VNC_ = VCOM_ or unconnected -1 -1 -0.1 (V+ - 1.2) V SYMBOL CONDITIONS MIN TYP MAX UNITS
Voltage Between COM and NO/NC
0
1.8
V
On-Resistance On-Resistance Match Between Pairs of Same Channel On-Resistance Match Between Channels On-Resistance Flatness NO_ or NC_ Off-Leakage Current COM_ On-Leakage Current
7 0.1 0.6 0.06 1 2 2 +1 +1
A A
2
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2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 3.0V to 3.6V, TA = -40C to +85C, unless otherwise noted. Typical values are at V+ = 3.3V, TA = +25C.) (Note 2)
PARAMETER DYNAMIC Turn-On Time Turn-Off Time Propagation Delay Output Skew Between Pairs Output Skew Between Same Pair On-Loss SYMBOL tON tOFF tPD tSK1 tSK2 CONDITIONS VNO_ or VNC_ = 1.0V, RL = 50, Figure 1 VNO_ or VNC_ = 1.0V, RL = 50, Figure 1 RS = RL = 50, unbalanced, Figure 2 RS = RL = 50, unbalanced; skew between any two pairs, Figure 2 RS = RL = 50, unbalanced; skew between two lines on same pair, Figure 2 RS = RL = 50, unbalanced, Figure 3 Crosstalk between any two pairs, RS = RL = 50, unbalanced, Figure 3 RS = RL = 50 Signal = 0dBm, RS = RL = 50, Figure 3 Figure 4 f = 10MHz f = 1.25GHz 1MHz < f < 100MHz 500MHz < f < 1.25GHz f = 50MHz MIN TYP 90 10 50 50 10 -0.5 dB -1.4 -53 dB f = 1.25GHz -32 3.0 -56 dB -26 1 2 0.5 1.4 100 VSEL = 0V or V+ -1 1.65 VSEL = 0V or V+ MAX4888 MAX4889 +1 3.60 60 120 pF pF V V mV A V A Gbps MAX 250 50 UNITS ns ns ps ps ps
GLOS
Crosstalk
VCT1
Signaling Data Rate Off-Isolation NO_/NC_ Off-Capacitance COM_ On-Capacitance LOGIC INPUT Input-Logic Low Input-Logic High Input-Logic Hysteresis Input Leakage Current POWER SUPPLY Power-Supply Range V+ Supply Current
BR VISO
CNO_/NC_(OFF) Figure 4 CCOM_(ON) VIL VIH VHYST IIN V+ I+
Note 2: All units are 100% production tested at TA = +85C. Limits over the operating temperature range are guaranteed by design and characterization and are not production tested. Note 3: RON = RON (MAX) - RON (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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3
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
ON-RESISTANCE vs. VCOM (V+ = 1.8V)
MAX4888/89 toc01 MAX4888/89 toc02
ON-RESISTANCE vs. VCOM
10.0 9.5 9.0 8.5 RON () 8.0 7.5 7.0 6.5 6.0 5.5 5.0 -0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 VCOM (V) V+ = 3.3V 2 0 -0.1 0 V+ = 2.5V RON () V+ = 1.8V 14 12 10 8 6 4
ON-RESISTANCE vs. VCOM (V+ = 2.5V)
TA = +85C 12 10 RON () 8 6 4 2 0 TA = -40C TA = +25C
MAX4888/89 toc03
14
TA = +85C TA = +25C
TA = -40C
0.1
0.2 0.3 VCOM (V)
0.4
0.5
0.6
-0.1
0.1
0.3
0.5 0.7 VCOM (V)
0.9
1.1
1.3
ON-RESISTANCE vs. VCOM (V+ = 3.3V)
MAX4888/89 toc04
SUPPLY CURRENT vs. TEMPERATURE (MAX4888)
70 SUPPLY CURRENT (A) 60 V+ = 3.3V 50 40 30 20 10 0 -40 V+ = 1.8V -15 10 35 TEMPERATURE (C) 60 85 V+ = 2.5V
MAX4888/89 toc05
14 12 TA = +25C 10 RON () 8 6 4 2 0 TA = -40C TA = +85C
80
-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 VCOM (V)
4
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2.5Gbps PCI Express Passive Switches
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
EYE DIAGRAM (V+ = 1.8V, f = 1.25GHz, 600mVP-P PRBS SIGNAL, RS = RL = 50)
VCOM_+
MAX4888/89 toc08
MAX4888/MAX4889
LOGIC THRESHOLD vs. SUPPLY VOLTAGE
MAX4888/89 toc06
TURN-ON/-OFF TIME vs. SUPPLY VOLTAGE
240 220 200 180 160 tON/tOFF (ns) 140 120 100 80 60 40 20 0
MAX4888/89 toc07
1.2 1.1 LOGIC THRESHOLD (V) 1.0 0.9 0.8 VIL 0.7 0.6 0.5 VIH
NO_ tON
50mV/div NC_ tON NO_ tOFF NC_ tOFF VCOM_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) 50ps/div *PRBS = PSEUDORANDOM BIT SEQUENCE GEN I; 2.5Gps; UI = 400ps
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)
EYE DIAGRAM (V+ = 2.5V, f = 1.25GHz, 600mVP-P PRBS SIGNAL, RS = RL = 50)
MAX4888/89 toc09
EYE DIAGRAM (V+ = 3.3V, f = 1.25GHz, 600mVP-P PRBS SIGNAL, RS = RL = 50)
VCOM_+
MAX4888/89 toc10
VCOM_+
50mV/div
50mV/div
VCOM_50ps/div *PRBS = PSEUDORANDOM BIT SEQUENCE GEN I; 2.5Gps; UI = 400ps
VCOM_50ps/div *PRBS = PSEUDORANDOM BIT SEQUENCE GEN I; 2.5Gps; UI = 400ps
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5
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Pin Description
PIN MAX4888 1, 10, 12, 14, 20, 25, 27 2 3, 9 4 5 6 7 8, 11, 13, 19, 26, 28 15 16 17 18 21 22 23 24 -- -- -- -- -- -- -- -- -- -- -- -- EP MAX4889 1, 4, 10, 14, 17, 19, 21, 39, 41 9 -- 2 3 6 7 5, 8, 13, 18, 20, 30, 40, 42 31 32 33 34 35 36 37 38 11 12 15 16 22 23 24 25 26 27 28 29 EP NAME GND SEL N.C. COM1+ COM1COM2+ COM2V+ NO2NO2+ NO1NO1+ NC2NC2+ NC1NC1+ COM3+ COM3COM4+ COM4NO4NO4+ NO3NO3+ NC4NC4+ NC3NC3+ EP Ground 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. Positive-Supply Voltage Input. Connect V+ to a 1.65V to 3.6V supply voltage. Bypass V+ to GND with a 0.1F capacitor placed as close to the device as possible. (See the Board Layout section). 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. 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. FUNCTION
6
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2.5Gbps PCI Express Passive Switches
Test Circuits/Timing Diagrams
MAX4888/MAX4889
MAX4888/MAX4889
3.3V V+ COM_ LOGIC INPUT VOUT RL SEL LOGIC INPUT GND SWITCH OUTPUT 0V t ON CL VOUT 0.9 x V0UT t OFF VIH 50% VIL
t r < 5ns t f < 5ns
VN_
NO_ OR NC_
0.9 x VOUT
VOUT = VN_
CL INCLUDES FIXTURE AND STRAY CAPACITANCE. RL RL + RON
(
)
VN_ = VNO_ OR VNC_
Figure 1. Switching Time
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7
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Test Circuits/Timing Diagrams (continued)
3.3V V+ NO_+ OR NC_+
MAX4888/MAX4889
COM_+ OUT+ RL RISE-TIME PROPAGATION DELAY = tPLHX OR tPLHY FALL-TIME PROPAGATION DELAY = tPHLX OR tPHLY tSK1 = DIFFERENCE IN PROPAGATION DELAY (RISE-FALL) BETWEEN ANY TWO PAIRS OUTRL tSK2 = | tPLHX - tPHLY | OR | tPHLX - tPLHY | BETWEEN TWO LINES ON THE SAME PAIR
RS IN+
RS IN-
NO_- OR NC_-
COM_-
SEL
tINRISE 1.5V VIN+ 0V 1.5V VIN0V tOUTRISE tPLHX 1.5V VOUT+ 0V 1.5V VOUT0V tPHLY tPLHY 50% 50% 50% 50% 10% tPHLX 90% 50% 50% 50% 50% 10%
tINFALL
90%
90% 10%
tOUTFALL
90% 10%
Figure 2. Propagation Delay and Output Skew
8
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2.5Gbps PCI Express Passive Switches
Test Circuits/Timing Diagrams (continued)
3.3V 0.1F NETWORK ANALYZER 0V OR V+ SEL V+ COM_ VIN 50 50 V OFF-ISOLATION = 20log OUT VIN ON-LOSS = 20log VOUT VIN VOUT VIN
MAX4888/MAX4889
NC_ 50
MAX4888/MAX4889
NO_ VOUT MEAS REF
CROSSTALK = 20log
50 GND
50
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
0.1F
3.3V
V+ COM_
MAX4888/MAX4889
sets of eight lanes from a single 16-lane bus. The MAX4888/MAX4889 feature a single digital control input (SEL) to switch signal paths. The MAX4888/MAX4889 are fully specified to operate from a single 3.0V to 3.6V power supply and also operate down to 1.65V.
Digital Control Input (SEL)
SEL CAPACITANCE METER NC_ or NO_ GND VIL OR VIH
The MAX4888/MAX4889 provide a single digital control input (SEL) to select the signal path between the COM__ and NO__/NC__ channels. The truth tables for the MAX4888/MAX4889 are depicted in the Functional Diagrams/Truth Table section. Drive SEL rail-to-rail to minimize power consumption.
Analog Signal Levels
Figure 4. Channel Off-/On-Capacitance
Detailed Description
The MAX4888/MAX4889 high-speed passive switches route PCIe data between two possible destinations. The MAX4888/MAX4889 are ideal for routing PCIe signals to change the system configuration. For example, in a graphics application, the MAX4888/MAX4889 create two
The MAX4888/MAX4889 accept standard PCIe signals to a maximum of V+ - 1.2V. Signals on the COM_+ channels are routed to either the NO_+ or NC_+ channels, and signals on the COM_- channels are routed to either the NO_- or NC_- channels. The MAX4888/ MAX4889 are bidirectional switches, allowing COM__, NO__, and NC__ to be used as either inputs or outputs.
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9
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Functional Diagrams/Truth Table
V+ V+
MAX4888
COM1+ COM1NC1+ NC1NO1+ NO1COM2+ COM2NC2+ NC2NO2+ NO2SEL COM3+ COM3GND COM2+ COM2COM1+ COM1-
MAX4889
NC1+ NC1NO1+ NO1NC2+ NC2NO2+ NO2NC3+ NC3NO3+ NO3-
SEL 0 1
COM__ TO COM__ TO NC__ NO__ ON OFF OFF ON
COM4+ COM4-
NC4+ NC4NO4+ NO4-
SEL
GND
10
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2.5Gbps PCI Express Passive Switches
Applications Information
PCIe Switching
The MAX4888/MAX4889 primary applications are 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 prominent examples are SLITM (Scaled Link Interface) and CrossFireTM. The MAX4889 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.
ONE LANE DATA DIRECTION
MAX4888/MAX4889
MAX4888 MAX4889
NOTE: ONLY ONE LANE IS SHOWN FOR CLARITY
DATA IS ROUTED TO EITHER BOARD A OR B
Board Layout
High-speed switches require proper layout and design procedures for optimum performance. Keep designcontrolled 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.
A B
Figure 5. The MAX4888/MAX4889 Used as a Single-Lane Switch
Chip Information
PROCESS: CMOS
CrossFireTM is a trademark of ATI Technologies, Inc. SLITM is a trademark of NVIDIA Corporation.
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11
2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Typical Application Circuit
PCIe GRAPHICS INTERFACE GRAPHICS CARD 1 COM1+ LANE 0 TX COM1COM2+ LANE 1 TX COM2COM3+ LANE 2 TX COM3COM4+ LANE 3 TX COM4NC1+ NC1NC2+ GRAPHICS CARD 2
PCIe BUS
MAX4889
NC2NC3+ NC3NC4+ NC4NO1+ NO1NO2+ NO2NO3+ NO3NO4+
SEL
NO4-
CHANNEL SELECT
COM1+ LANE 0 RX COM1COM2+ LANE 1 RX COM2COM3+ LANE 2 RX COM3COM4+ LANE 3 RX COM4-
NC1+ NC1NC2+
MAX4889
NC2NC3+ NC3NC4+ NC4NO1+ NO1NO2+ NO2NO3+ NO3NO4+
SEL
NO4-
CHANNEL SELECT
12
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2.5Gbps PCI Express Passive Switches
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 28L THIN QFN.EPS 13
MAX4888/MAX4889
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2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
14
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2.5Gbps 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 go to www.maxim-ic.com/packages.) 42L THIN QFN.EPS 15
MAX4888/MAX4889
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2.5Gbps PCI Express Passive Switches MAX4888/MAX4889
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products. Inc. Products,

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