Maxim

19-0724; Rev 0; 5/07

2.5Gbps PCI Express Passive Switches

General Description

The MAX4888/MAX4889 high-speed passive switches route PCI Express ® (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 -40°C to +85°C temperature range.

Applications

Desktop Computers

Servers/Storage Area Networks

Laptops

PCI Express is a registered trademark of PCI-Sig Corp.

Features

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 Data Rates o Flow-Through Pin Configuration for Ease of

Layout o Industry-Compatible Pinout o Lead-Free Packaging

Ordering Information/

Selector Guide

PART

PIN-

PACKAGE

CONFIGURATION

PKG

CODE

MAX4888ETI+ 28 TQFN-EP*

MAX4889ETO+ 42 TQFN-EP*

Two

Half Lanes

Four Half

Lanes

T283555-1

T423590M-1

Note: All devices are specified over the -40°C to +85°C operating temperature range.

+ Denotes lead-free package.

* EP = Exposed paddle.

Typical Application Circuit appears at end of data sheet.

Pin Configurations

TOP VIEW

24 23 22 21 20 19 18 17 16 15

GND 25

V+ 26

GND 27

V+ 28

+

*EP

MAX4888

1 2 3 4 5 6 7 8 9 10

14 GND

13 V+

12 GND

11 V+

38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22

GND 39

V+ 40

GND 41

V+ 42

*EP

MAX4889

+

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

21 GND

20 V+

19 GND

18 V+

TQFN TQFN

*CONNECT EXPOSED PADDLE TO GROUND.

________________________________________________________________ Maxim Integrated Products 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.


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 (T

A

= +70°C)

28-Pin TQFN (derate 20.8mW/°C above +70°C) ....1666.7mW

42-Pin TQFN (derate 35.7mW/°C above +70°C) ....2857.1mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Junction Temperature ......................................................+150°C

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, T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at V+ = 3.3V, T

A

= +25°C.) (Note 2)

PARAMETER

ANALOG SWITCH

SYMBOL CONDITIONS MIN TYP MAX UNITS

Analog-Signal Range

V

COM_

,

V

NO_,

V

NC_

-0.1

(V+ - 1.2) V

Voltage Between COM and

NO/NC

| V

COM_

-

V

NO_

| ,

| V

COM_

-

V

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

R

FLAT(ON)

I

I

R

ΔR

ΔR

ON

ON

ON

NO_(OFF)

NC_(OFF)

I

COM_(ON)

V+ = 3.0V, I

COM_

= 15mA,

V NO_ or V NC_ = 0V, 1.8V

V+ = 3.0V, I

COM_

= 15mA,

V

NO_

or V

NC_

= 0V (Notes 3, 4)

V+ = 3.0V, I

COM_

= 15mA,

V

NO_

or V

NC_

= 0V (Notes 3, 4)

V+ = 3.0V, I

COM_

= 15mA

V

NO_

or V

NC_

= 0V, 1.8V (Notes 4, 5)

V+ = 3.6V; V

COM_

= 0V, 1.8V;

V

NO_

or V

NC_

= 1.8V, 0V

V+ = 3.6V; V

COM_

= 0V, 1.8V;

V

NO_

or V

NC_

= V

COM_ or unconnected

-1

-1

7

0.1

0.6

0.06

1

2

2

+1

+1

Ω

Ω

Ω

Ω

µA

µA

2 _______________________________________________________________________________________


ELECTRICAL CHARACTERISTICS (continued)

(V+ = 3.0V to 3.6V, T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at V+ = 3.3V, T

A

= +25°C.) (Note 2)

SYMBOL CONDITIONS MIN TYP MAX UNITS PARAMETER

DYNAMIC

Turn-On Time

Turn-Off Time

Propagation Delay

Output Skew Between Pairs

Output Skew Between Same

Pair

On-Loss t

ON t

OFF t

PD t

SK1 t

SK2

G

LOS

V

NO_

or V

NC_

= 1.0V, R

L

= 50

Ω, Figure 1

V

NO_

or V

NC_

= 1.0V, R

L

= 50

Ω, Figure 1

R

S

= R

L

= 50 Ω, unbalanced, Figure 2

R

S

= R

L

= 50

Ω, unb al anced ; skew b etw een any tw o p ai r s, Fi g ur e 2

R

S

= R

L

= 50

Ω, unb al anced ; skew b etw een tw o l i nes on sam e p ai r , Fi g ur e 2

R S = R L = 50

Ω, unbalanced,

Figure 3

1MHz <

500M H z f <

< f

100MHz

< 1.25G H z

90

10

50

50

10

-0.5

-1.4

250

50 ns ns ps ps ps dB

Crosstalk

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

V

CT1

BR

Crosstalk between any two pairs,

R

S

= R

L

= 50 Ω, unbalanced,

Figure 3

R

S

= R

L

= 50

Ω

V

ISO

Signal = 0dBm,

R

S

= R

L

= 50

Ω,

Figure 3

C

N O_/N C _( OFF) Figure 4

C

COM_(ON)

Figure 4

V

IL

V

IH

V

HYST

I

IN

V+

I+

V

SEL

= 0V or V+

V

SEL

= 0V or V+ f = 50MHz f = 1.25GHz

f = 10MHz f = 1.25GHz

MAX4888

MAX4889

1.4

-1

1.65

-53

-32

3.0

-56

-26

1

2

100

0.5

+1

3.60

60

120 dB

Gbps dB pF pF

V

V mV

µA

V

µA

Note 2: All units are 100% production tested at T

A

= +85°C. Limits over the operating temperature range are guaranteed by design and characterization and are not production tested.

Note 3: ΔR

ON

= R

ON (MAX)

- R

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.

_______________________________________________________________________________________ 3


Typical Operating Characteristics

(T

A

= +25°C, unless otherwise noted.)

ON-RESISTANCE vs. V

COM

10.0

9.5

9.0

8.5

8.0

V+ = 1.8V

V+ = 2.5V

7.5

7.0

6.5

6.0

V+ = 3.3V

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

V

COM

(V)

10

8

6

14

12

4

2

0

-0.1

0


COM

(V+ = 1.8V)

T

A

= +85°C

T

A

= +25°C

T

A

= -40°C

0.1

0.2

0.3

0.4

0.5

0.6

V

COM

(V)

10

8

6

14

12


COM

(V+ = 2.5V)

T

A

= +25 °C

T

A

= +85 °C

4

2 T

A

= -40 °C

0

-0.1

0.1

0.3

0.5

0.7

0.9

1.1

1.3

V

COM

(V)


COM

(V+ = 3.3V)

14

12

10

T

A

= +25°C

T

A

= +85°C

8

6

4

2

T

A

= -40°C

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

COM

(V)

60

50

40

30

80

70

20

10

0

-40

SUPPLY CURRENT vs. TEMPERATURE

(MAX4888)

V+ = 3.3V

V+ = 2.5V

V+ = 1.8V

-15 10 35

TEMPERATURE (°C)

60 85

4 _______________________________________________________________________________________


(T

A

= +25°C, unless otherwise noted.)

0.9

0.8

0.7

1.2

LOGIC THRESHOLD vs. SUPPLY VOLTAGE

1.1

1.0

V

IH

V

IL

0.6

0.5

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)

Typical Operating Characteristics (continued)

TURN-ON/-OFF TIME vs. SUPPLY VOLTAGE

240

220

200

180

160

140

120

NO_ t

ON

100

80

60

40

20

NC_ t

NO_ t

ON

OFF

NC_ t

OFF

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)

V

COM_+

50mV/div

EYE DIAGRAM

600mV

(V+ = 1.8V, f = 1.25GHz,

P-P

PRBS SIGNAL, R

S

= R

L

= 50Ω)

†

V

COM_-

50ps/div

*PRBS = PSEUDORANDOM BIT SEQUENCE

†

GEN I; 2.5Gps; UI = 400ps

V

COM_+

EYE DIAGRAM

(V+ = 2.5V, f = 1.25GHz,

600mV

P-P

PRBS SIGNAL, R

S

= R

L

= 50Ω)

†

V

COM_+

EYE DIAGRAM

(V+ = 3.3V, f = 1.25GHz,

600mV

P-P

PRBS SIGNAL, R

S

= R

L

= 50Ω)

†

50mV/div 50mV/div

V

COM_-

50ps/div


†


V

COM_-

50ps/div


†


_______________________________________________________________________________________ 5


Pin Description

—

—

—

—

—

EP

—

—

—

—

21

22

23

24

15

16

17

18

—

—

—

MAX4888

1, 10, 12, 14,

20, 25, 27

2

3, 9

6

7

4

5

PIN

8, 11, 13, 19,

26, 28

MAX4889

1, 4, 10, 14, 17,

19, 21, 39, 41

9

—

6

7

2

3

5, 8, 13, 18,

20, 30,

40, 42

16

22

27

28

29

EP

23

24

25

26

35

36

37

38

31

32

33

34

11

12

15

NAME FUNCTION

GND Ground

SEL

N.C.

Digital Control Input

No Connection. Not internally connected.

COM1+ Analog Switch 1. Common Positive Terminal.

COM1Analog Switch 1. Common Negative Terminal.



V+

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).

NO2-

NO2+

NO1-

NO1+

NC2-

NC2+

NC1-

NC1+

Analog Switch 2. Normally Open Negative Terminal.

Analog Switch 2. Normally Open Positive Terminal.



Analog Switch 2. Normally Closed Negative Terminal.

Analog Switch 2. Normally Closed Positive Terminal.







NO4Analog Switch 4. Normally Open Negative Terminal.

NO4+

NO3-

NO3+

NC4-

NC4+

NC3-

NC3+

EP








Exposed Paddle. Connect EP to GND.

6 _______________________________________________________________________________________

MAX4888/MAX4889


Test Circuits/Timing Diagrams

LOGIC

INPUT

V

N_

NO_

OR NC_

SEL

GND

3.3V

V+

COM_

R

L

C

L

V

OUT

LOGIC

INPUT

V

V

IH

IL

SWITCH

OUTPUT

0V tr < 5ns tf < 5ns

50%

V

OUT

0.9 x V

0UT t

ON t

OFF

0.9 x V

OUT

C

L

INCLUDES FIXTURE AND STRAY CAPACITANCE.

V

OUT

= V

N_

(

R

L

L

+ R

ON

)

V

N_

= V

NO_

OR V

NC_

Figure 1. Switching Time

_______________________________________________________________________________________ 7


IN+

IN-

Test Circuits/Timing Diagrams (continued)

3.3V

V+

R

S

NO_+ OR

NC_+

MAX4888/MAX4889

COM_+

R

S

NO_- OR

NC_COM_-

R

L

OUT+

OUT-

RISE-TIME PROPAGATION DELAY = t

PLHX

OR t

PLHY

FALL-TIME PROPAGATION DELAY = t

PHLX

OR t

PHLY t

SK1

= D I F F E R E N C E I N P R O PA G AT I O N D E L AY ( R I S E - FA L L )

BETWEEN ANY TWO PAIRS t

SK2

= | t

PLHX

- t

PHLY

| OR | t

PHLX

- t

PLHY

|

BETWEEN TWO LINES ON THE SAME PAIR

R

L

SEL

V

IN+

1.5V

0V

V

IN-

1.5V

0V

V

OUT+

1.5V

0V

1.5V

V

OUT-

0V t

PLHX t

PHLY

50%

50%

50%

50% t

PHLX t

PLHY

50%

50%

50%

50% t

INRISE

10%

90% t

OUTRISE

10%

90% t

INFALL

90%

10% t

OUTFALL

90%

10%

Figure 2. Propagation Delay and Output Skew

8 _______________________________________________________________________________________


Test Circuits/Timing Diagrams (continued)

3.3V

0.1μF

0V OR V+

50Ω

V+

SEL

COM_

NC_

MAX4888/MAX4889

NO_

GND

V

IN

V

OUT

MEAS

50Ω

50Ω

NETWORK

ANALYZER

50Ω

50Ω

REF

OFF-ISOLATION = 20log

V

V

OUT

IN

ON-LOSS = 20log

V

OUT

V

IN

CROSSTALK = 20log

V

OUT

V

IN

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

CAPACITANCE

METER

0.1μF

3.3V

V+

COM_ MAX4888/MAX4889

NC_ or

NO_

GND

SEL

V

IL

OR V

IH

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 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)

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

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.

_______________________________________________________________________________________ 9


COM1+

COM1-

COM2+

COM2-

SEL

V+

MAX4888

GND

SEL

COM__ TO

NC__

COM__ TO

NO__

0

1

ON

OFF

OFF

ON

NC1+

NC1-

NO1+

NO1-

NC2+

NC2-

NO2+

NO2-

COM1+

COM1-

COM2+

COM2-

COM3+

COM3-

COM4+

COM4-

Functional Diagrams/Truth Table

V+

MAX4889

NC2-

NO2+

NO2-

NC3+

NC3-

NC1+

NC1-

NO1+

NO1-

NC2+

NO3+

NO3-

NC4+

NC4-

NO4+

NO4-

SEL

GND

10 ______________________________________________________________________________________


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 SLI™ (Scaled Link Interface) and

CrossFire™. 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.

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.

ONE LANE

MAX4888

MAX4889

DATA

DIRECTION

NOTE: ONLY ONE LANE IS SHOWN FOR CLARITY

DATA IS ROUTED

TO EITHER

BOARD A OR B

A

Figure 5. The MAX4888/MAX4889 Used as a Single-Lane

Switch

B

Chip Information

PROCESS: CMOS

CrossFire is a trademark of ATI Technologies, Inc.

SLI is a trademark of NVIDIA Corporation.

______________________________________________________________________________________ 11


Typical Application Circuit

PCIe GRAPHICS INTERFACE

COM1+

COM1-

COM2+

COM2-

COM3+

COM3-

COM4+

COM4-

MAX4889

GRAPHICS

CARD 1

GRAPHICS

CARD 2

PCIe BUS

LANE 0 TX

LANE 1 TX

LANE 2 TX

LANE 3 TX

NC1+

NC1-

NC2+

NC2-

NC3+

NC3-

NC4+

NC4-

NO1+

NO1-

NO2+

NO2-

NO3+

NO3-

NO4+

NO4-

SEL

CHANNEL SELECT

LANE 0 RX

LANE 1 RX

LANE 2 RX

LANE 3 RX

COM1+

COM1-

COM2+

COM2-

COM3+

COM3-

COM4+

COM4-

MAX4889

NC4+

NC4-

NO1+

NO1-

NO2+

NC1+

NC1-

NC2+

NC2-

NC3+

NC3-

NO2-

NO3+

NO3-

NO4+

NO4-

SEL

CHANNEL SELECT

12 ______________________________________________________________________________________


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 .)

°

______________________________________________________________________________________ 13


Package Information (continued)


14 ______________________________________________________________________________________




°

______________________________________________________________________________________ 15




Maxim | /MAX4889A | User manual | MAX4888/MAX4889 2.5Gbps PCI Express Passive Switches

General Description

Applications

Features

Ordering Information/

Selector Guide

Pin Configurations

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.

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

ELECTRICAL CHARACTERISTICS (continued)

Typical Operating Characteristics

Typical Operating Characteristics (continued)

Pin Description

Test Circuits/Timing Diagrams

Test Circuits/Timing Diagrams (continued)

Test Circuits/Timing Diagrams (continued)

Detailed Description

Digital Control Input (SEL)

Analog Signal Levels

Functional Diagrams/Truth Table

Applications Information

PCIe Switching

Board Layout

Chip Information

Typical Application Circuit

Package Information

Package Information (continued)

Package Information (continued)

Package Information (continued)

Related manuals

MAX4888AETI+

Maxim

MAX4888AETI+