max5950 ev kit - maxim integrated · pdf filemax5950 ev kit also includes connections for the...

General DescriptionThe MAX5950 evaluation kit (EV kit) is a fully assembledand tested surface-mount circuit board featuring a PWMstep-down DC-DC controller with integrated hot-swapcapabilities for PCIe® ExpressModule™. The circuitboard has an X8E PCIe ExpressModule form factor. TheEV kit’s circuit uses a MAX5950 and two MAX5951 ICs in32-pin thin QFN packages. The MAX5950 EV kit pro-vides outputs of 1.2V at 2.5A, and 2.5V and 3.3V witheach providing 1.25A.

The MAX5950 EV kit demonstrates the MAX5950 IC’shot-swap inrush current control capabilities as well asthe MAX5950 and MAX5951 ICs’ hiccup-mode outputshort-circuit protection during normal operation. TheMAX5950 controls an external n-channel MOSFET forinrush control during hot swapping. The EV kit canoperate over an 8V to 16V input range, however, it isconfigured for 12V input operation by default. TheMAX5950 EV kit also includes connections for the PCIebus 3.3V auxiliary supply.

Additionally, the MAX5950 and MAX5951 PWM DC-DCstep-down controllers’ lossless current sensing, digitalsoft-start, startup synchronization, thermal shutdown,and hiccup-mode output short-circuit current-limitfeatures can be evaluated using the EV kit. The VOUT1circuit can also be reconfigured to evaluate an alternatecurrent-sense method using a resistor for the DC-DCconverter. The hot-swap and PWM undervoltagelockouts (UVLO) can easily be reconfigured for other set points. The MAX5950 EV kit can be reconfiguredfor various startup tracking/sequencing modes suchas ratiometric-tracking, startup sequencing, PGOODsequencing. The EV kit is configured for PGOODsequencing by default.

To ease bench evaluation of the MAX5950 EV kit, aMAX5950PB power board assembly is included with theEV kit. The power board features bulk holdup capaci-tance for the 12V and 3.3V auxiliary power rails providingpower to a single X8E PCIe connector. The power boardincludes switches, HC logic, and LEDs to simulate hotswapping a MAX5950 EV kit into a server’s backplane uti-lizing an X8E PCIe connector.

The MAX5950 EV kit is not optimized for size, but isdesigned for ease of lab evaluation. See Appendix A,which shows a compact reference design with thesame output voltages and currents. The referencedesign is configured for PGOOD sequencing.

Features Demonstrates PCIe ExpressModule Hot-Swap and

DC-DC Design

Outputs1.2V at 2.5A2.5V at 1.25A3.3V at 1.25A

X8E PCIe ExpressModule Form Factor

Demonstrates Inrush Current Control andLossless Current Sensing

Demonstrates Output Overcurrent/Short-CircuitProtection

Configurable PWM and Hot-Swap UVLO

Configurable for Several StartupTracking/Sequencing Modes

Power Board Assembly Eases Bench Evaluation

Surface-Mount Components

Fully Assembled and Tested

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MAX5950 Evaluation Kit

________________________________________________________________ Maxim Integrated Products 1

19-0578; Rev 0; 6/06

MAX5950 EV Kit Component List

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering InformationPART TEMP RANGE IC PACKAGE

MAX5950EVKIT 0°C to +70°C 32 TQFN-EP*

DESIGNATION QTY DESCRIPTION

C1 1100µF ±20%, 6.3V X5R capacitor(1210)Murata GRM32ER60J107M

C2 10.001µF ±10%, 50V X7R capacitor(0805)Murata GRM216R71H102K

C3, C4 222µF ±10%, 16V X5R ceramiccapacitors (1210)Murata GRM32ER61C226KE20

C5, C8, C45,C48, C85, C88

61µF ±10%, 16V X7R ceramiccapacitors (0805)Murata GRM21BR71C105K

C6, C7, C46,C47, C86, C87

62.2µF ±10%, 10V X7R ceramiccapacitors (0805)Murata GRM21BR71A225K

C9 11000pF ±5%, 100V C0G ceramiccapacitor (0805)Murata GRM2195C2A102J

PCIe is a registered trademark and ExpressModule is a trade-mark of PCI-SIG Corp.

*EP = Exposed paddle.

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2 _______________________________________________________________________________________

MAX5950 EV Kit Component List (continued)DESIGNATION QTY DESCRIPTION

C10, C11, C50,C90

4

22µF ±20%, 6.3V X5R capacitors(1206)Murata GRM31CR60J226ME19ONLY use this specific capacitor

C12 1820pF ±5%, 50V C0G ceramiccapacitor (0603)Murata GRM1885C1H821J

C13, C53, C93 3220pF ±10%, 50V X7R ceramiccapacitors (0603)Murata GRM188R71H221K

C14, C54, C94 30.033µF ±10%, 50V X7R ceramiccapacitors (0603)Murata GRM188R71H333K

C15, C49, C89 0Not installed, ceramic capacitors(0805)

C44, C84 2

10µF ±10%, 16V X5R capacitors(1206)Murata GRM31CR61C106KC31BONLY use this specific capacitor

C52, C92 21500pF ±10%, 50V X7R ceramiccapacitors (0603)Murata GRM188R71H152K

D1 1 Green, right-angle LED (T-1 3/4)

D2 1 Yellow, right-angle LED (T-1 3/4)

D3, D43, D83 3 Green surface-mount LEDs (1206)

D4, D44, D84 3300mA, 75V switching diodes (SOD-323)Diodes Inc 1N4148WS-F

L1 11µH, 3.5A inductorPulse PG0063.102NL

L41 16.8µH, 1.5A inductorPulse PG0063.682NL

L81 110µH, 1.2A inductorPulse PG0063.103NL

N1 130V, 2.5A n-channel MOSFET(TSOP-6)Vishay Si3948DV-T1-E3

N2 120V, 5.3A n-channel MOSFET(PowerPack 1212-8)Vishay Si7212DN-T1-E3

N3, N43 220V, 1.9A n-channel MOSFETs(SC70-6)Fairchild FDG311N_NL

N42, N82 220V, 3.1A n-channel MOSFETs(1206-8 chipFET)Vishay Si5904DC-T1-E3

R1 1 7.5Ω ±5% resistor (1210)


R2–R5, R21,R27, R30, R31,R33, R35, R36,R39, R44, R45,R50, R64, R67,R84, R85, R90,

R104, R107

0 Not installed, resistors (0805)

R6, R12 0 Not installed, resistors (0603)

R7, R11 2 0Ω ±5% resistors (0603)

R8, R48, R88 3 5.6Ω ±5% resistors (0805)

R9, R49 2 910Ω ±5% resistors (0805)

R10 1 10Ω ±5% resistor (0805)

R13 0

Not installed, resistor (0805)0.033Ω ±1%, 0.25W resistorPanasonic ERJL06KF33MV orIRC LRC-LR0805LF-01-R033-Frecommended

R14 1 576Ω ±1% resistor (0603)

R15, R55, R95 310kΩ ±0.5% resistors (0805)Panasonic ERJ6RBD103V

R16 1

20kΩ ±0.5% resistor (0805)Panasonic ERJ6RBD203V orVishay TNPW-0805 20kΩ±5% T-2RT1

R18 1 5.23kΩ ±1% resistor (0805)

R19, R59, R99 3 15kΩ ±1% resistors (0805)

R20 1 2.15kΩ ±1% resistor (0805)

R22 1 48.7kΩ ±1% resistor (0805)

R23 1 49.9kΩ ±1% resistor (0805)R24, R28, R32,R34, R37, R38,

R68, R1088 0Ω ±5% resistors (0805)

R25, R26, R89 3 110Ω ±5% resistors (0805)

R54, R94 2 133Ω ±1% resistors (0805)

R56 1

4.70kΩ ±0.5% resistor (0805)Vishay TNPW-0805 4.7kΩ ±0.5%T-9RT1 orPanasonic ERJ6RBD472V

R57 1 10Ω ±1% resistor (0805)

R58 1 27.4kΩ ±1% resistor (0805)

R60, R100 2 3.83kΩ ±1% resistors (0805)

R62, R102 2 34kΩ ±1% resistors (0805)

R63, R103 2 59.0kΩ ±1% resistors (0805)

R96 1 3.16kΩ ±0.5% resistor (0805)

Quick StartRequired equipment:

• One each of the following DC power supplies12V, 2A3.3V, 1A

• One voltmeter

The MAX5950 EV kit is fully assembled and tested.Follow these steps to verify board operation. Do notturn on the power supply until all connections are com-pleted.

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_______________________________________________________________________________________ 3


R97 1 39.2Ω ±1% resistor (0805)

R98 1 40.2kΩ ±1% resistor (0805)

VOUT1, VOUT2,VOUT3

3 PC test points, red

PGND, PGND,PGND, PGND,PGND, GND1,GND2, GND3

8 PC test points, black

PWREN,PWRFLT,

MPWRGD,+12VIN,+12VHS

5 PC test points, miniature, red

U1 1MAX5950ETJ+ (32-pin TQFN, 5mmx 5mm)Package code: T3255-4

U41, U81 2MAX5951ETJ+ (32-pin TQFN, 5mmx 5mm)Package code: T3255-4

— 1MAX5950EVKIT circuit boardassembly

— 1X8E PCIe Express power boardassemblyMaxim MAX5950PB

MAX5950PB Power BoardAssembly Component List


C1 1150µF, 6.3V low-Z electrolyticcapacitor (6.3mm x 6mm case)Sanyo 6.3CE150KX

C2, C8, C9 31µF ±10%, 16V X7R ceramiccapacitors (0805)Murata GRM21BR71C105K

C3–C7 5680µF, 16V electrolytic capacitors(10mm x 10.2mm case)Sanyo 16CE680KX

D1, D2 2 Yellow surface-mount LEDs (1206)

D3 1 Red surface-mount LED (1206)

D4, D5 2 Green surface-mount LEDs (1206)

J1 1X8E PCIe Express connector(140 pins)Molex 48230-1015

R1 1 62Ω ±5% resistor (0805)

R2 1 510Ω ±5% resistor (0805)

R3, R4 2 620Ω ±5% resistors (0805)

R5 1 10kΩ ±5% resistor (0805)

R6 1 150Ω ±5% resistor (0805)

R7, R8 2 100kΩ ±5% resistors (0805)

SW1, SW2, SW3 3 SPST slide switches

+12V, PGND,PGND, +VAUX

4 Uninsulated banana jacks

TP1–TP5, TP7 6 PC test points, miniature red

TP6 1 PC test point, miniature black

U1 1HC quad 2-input AND gate(14-SOP)Texas Instruments SN74HC08NSR

— 1X8E PCIe Express power boardassembly(MAX5950PB)

— 5 Rubber bumpers

+Denotes lead-free package.

MAX5950EV Kit Component List(continued)

Component SuppliersSUPPLIER PHONE WEBSITE

Diodes Inc 805-446-4800 www.diodes.com

Fairchild 888-522-5372 www.fairchildsemi.com

IRC 361-992-7900 www.irctt.com

Molex ConnectorCorp

800-786-6539 www.molex.com

Murata 770-436-1300 www.murata.com

Panasonic 714-373-7366 www.panasonic.com

PulseEngineering

858-674-8100 www.pulseeng.com

Sanyo ElectronicDevice

619-661-6835 www.sanyodevice.com

Vishay — www.vishay.com

Note: Indicate that you are using the MAX5950 when contact-ing these component suppliers.

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51 Note: The banana leads connecting the 12V and 3.3V

power supply to the EV kit must be short (< 24in long).

MAX5950 EV Kit and MAX5950PB PowerBoard Assembly Configuration

1) The MAX5950 EV kit is configured by default forPGOOD sequencing startup.

2) Set switches SW1, SW2, and SW3 to the OFF posi-tion on the MAX5950PB power board.

MAX5950PB Power Board Assembly Connections1) Utilizing short 5A-rated banana leads (< 24in long)

connect the supply ground to the PGND bananajack. Utilizing short 5A-rated banana leads (< 24inlong) connect the 12V DC power supply to the adja-cent +12V banana jack.

2) Utilizing a short banana lead (< 24in long) connectthe supply ground to the PGND banana jack.Utilizing a short banana lead (< 24in long) connectthe 3.3V DC power supply to the adjacent +VAUXbanana jack.

3) Test points TP1–TP5 and TP7 on the MAX5950PBpower board are provided to observe various sys-tem hot-swap signals. TP6 is PGND.

Hot Swapping the MAX5950 EV Kit1) Turn on the power supplies sourcing the

MAX5950PB power board in any sequence.

2) Set switches SW1 (PWRLED), SW2 (ATNLED), andSW3 (PWREN) to the ON position.

3) Plug the MAX5950 EV kit into the MAX5950PB powerboard assembly.

4) Verify that the following green LEDs on the MAX5950EV kit are as shown below.

VOUT1, D3 = ONVOUT2, D43 = ONVOUT3, D83 = ON

5) Verify that the voltage at the following pads andPGND on the MAX5950 EV kit are as shown below.

VOUT1 = 1.2VVOUT2 = 2.5VVOUT3 = 3.3V

6) Verify that the following LEDs on the MAX5950PBpower board and EV kit are as shown below.

MAX5950PB power board:+12V, yellow D1 = ON+VAUX, yellow D2 = ONPWRFLT, red D3 = OFFMPWRGD, green D4 = ONPWREN, green D5 = ON

MAX5950 EV kit:PWRLED, green D1 = ONATNLED, yellow D2 = ON

7) Sliding switches SW1 and/or SW2 to the OFF posi-tion will disable the PWRLED and ATNLED on theMAX5950 EV kit. Also, sliding switches SW1 andSW3 to the ON position will turn on LED D5 on thepower board assembly and the PWRLED andATNLED on the MAX5950 EV kit.

8) Sliding switch SW3 to the OFF position will disablethe MAX5950 EV kit’s outputs and reset all three DC-DC controllers on the MAX5950 EV kit.

9) Test points TP1–TP7 on the MAX5950 EV kit are pro-vided to observe each MOSFET’s gate voltage,respectively, with an oscilloscope.

See the MAX5950PB Power Board Assembly sectionfor configuring and using the power board.

Detailed DescriptionThe MAX5950 EV kit demonstrates a hot-swap andtriple-output DC-DC converter circuit design on an X8EPCIe ExpressModule form-factor PC board. The EV kitis configured for 12V input operation by default, howev-er, it can operate from an input range of 8V to 16V withsuitable reconfiguration. The MAX5950 EV kit includesa passive PCIe Express 3.3V auxiliary supply bus.Resistor R1 limits the precharge current and time forthe 3.3V auxiliary supply bus capacitor, C1.

A MAX5950 (U1) PWM step-down DC-DC controllerwith integrated hot-swap capabilities provides the hot-swapping control features and regulates the main out-put providing 1.2V at 2.5A. Two MAX5951 controllers(U41, U81) regulate the other outputs, providing 2.5Vand 3.3V at 1.25A each.

The EV kit demonstrates the MAX5950 IC’s hot-swapinrush current control, as well as hiccup-mode outputshort-circuit protection during normal operation. TheMAX5950 drives a dual n-channel MOSFET (N1) whilehot swapping and thus limits inrush current during thehot-swapping event. Inrush current is sensed acrossN1’s drain-source resistance by the MAX5950, thusproviding short-circuit protection after successful hotswapping. The current-sensing feature can be disabledby reconfiguring resistors R7 and R6. During a fault,the MAX5950 circuit breaker function latches thePWRFAULT pin to indicate a fault has occurred. Toreset U1, cycle the input power or momentarily pull thePWREN pin high. The MAX5950 hot-swap UVLOthreshold is set to 7V, however, other UVLO values canbe evaluated by installing resistors R2 and R3.


4 _______________________________________________________________________________________

The MAX5950 controller regulates the main output volt-age at VOUT1 by driving MOSFETs N2A and N2B.Voltage-mode control is used along with feedbackresistors R15 and R16 to set the voltage to 1.2V. RCnetwork R14 to R16, R20, and C12 to C14 form thecompensation network for this output. The MAX5950switches at a 1MHz frequency and that is set by resis-tor R23. The SYNCOUT pin of U1 drives the SYNCINpins of both MAX5951 controllers. The PWM UVLOthreshold is set to 7V, however, other UVLO settingscan be evaluated by installing resistors R4 and R5.

Separate MAX5951 controllers regulate the two otheroutputs, VOUT2 and VOUT3. IC U41, a MAX5951, dri-ves MOSFETs N42A and N42B and utilizes voltage-mode control along with feedback resistors R55, R56,and R57 to set VOUT2 at 2.5V. RC network R54–R57,R60, and C52 to C54 form the compensation networkfor this output. IC U81, a MAX5951, drives MOSFETsN82A and N82B and utilizes voltage-mode controlalong with feedback resistors R95, R96, and R97 to setVOUT3 at 3.3V. RC network R94, R100, and C92 to C94form the compensation network for this output.

The VOUT2 and VOUT3 converters switch at 1MHz andare driven by the SYNCOUT pin of U1. Both U41 andU81 switch 180 degrees out-of-phase with respect toU1. Each converter’s PWM UVLO is set by a resistor-divider. To evaluate a specific PWM UVLO different thanthe default, select and install the required resistors.

All three outputs are configured for lossless valley cur-rent sensing by default. However, output 1 can bereconfigured to use a current-sense resistor. See theCurrent-Limiting (ILIM) section for reconfiguring thecurrent-sensing method. The MAX5950 EV kit demon-strates all three output’s respective controllers’ digitalsoft-start, thermal shutdown, and hiccup-mode outputshort-circuit current-limit features.

The MAX5950 EV kit is configured for PGOODsequencing by default. The EV kit can also be reconfig-ured for ratiometric tracking or startup sequencing. Seethe Startup Tracking/Sequencing Modes for reconfigur-ing the startup mode.

The MAX5950 EV kit features a green PWRLED LEDand yellow ATNLED LED to indicate connectivity whenthe EV kit is currently powered. Red test points areincluded for probing various signals. All of the EV kit’sblack test points are PGND or GND points.

The EV kit includes an X8E PCIe power board(MAX5950PB) assembly that includes bulk-holdupcapacitance for the PCIe 12V and 3.3V auxiliary powerrails. The MAX5950PB provides power to a single X8EPCIe connector, J1. The power board assemblyincludes three switches, HC logic, and LEDs that facili-tate the simulation of hot swapping a MAX5950 EV kitinto a server’s backplane. See the MAX5950PB PowerBoard Assembly section for more information on theMAX5950PB assembly.

EV Kit ReconfigurationThe following table displays the various configurablefunctions provided by the MAX5950 and MAX5951 ICsused on the MAX5950 EV kit. Information on compo-nent replacement or removal is provided.

Startup Tracking/Sequencing ModesThe MAX5950 EV kit is configured for PGOODsequencing by default. The EV kit can be reconfiguredfor one of three startup tracking/sequencing modessuch as ratiometric tracking, startup sequencing, orPGOOD sequencing. To reconfigure the EV kit foranother mode, install or remove the appropriate sur-face-mount (0805 case) resistor and/or capacitor asdetailed in Table 1.

Chart 1 illustrates the required connections for the threestartup modes: tracking, startup sequencing, andPGOOD sequencing.

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MODE OPEN RESISTORS 0Ω RESISTORSCAPACITOR AND 1% RESISTORS TO BE

CALCULATED

PGOOD Sequencing(default)

R21, R27, R30, R31, R33,R35, R36, R39, R67,

R107

R28, R32, R34, R37, R68,R108

—

Ratiometric TrackingR27, R32, R34, R39, R67,

R107R28, R30, R31, R33,R35–R38, R68, R108

—

STARTUP Sequencing R32, R34 R30, R31, R33, R35–R39 C15, R22, R27, R28, R67, R68, R107, R108

Table 1. Startup Tracking/Sequencing Modes Configurations

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Hot-Swap Controls and Other DC-DCConverter Configurations

Hot-Swap UVLO Configuration (HUVLO)The MAX5950 hot-swap UVLO is configured for 7V(typ) on the rising +12VIN input voltage by default.Other hot-swap UVLOs can be evaluated by selectingand installing resistors R2 and R3 (0805 case). Usingthe desired startup voltage, calculate the resistor R2value using the following equation:

where VINSTARTUP is the desired hot-swap startup volt-age (≥ 7V) and resistor R3 is typically 10kΩ. Refer to theMAX5950 data sheet for additional information on theHUVLO pin.

Hot-Swap Sense Input Configuration (HSENSE)The MAX5950 monitors input current by sensing thevoltage across MOSFET N1. Once the MOSFET is fullyenhanced after hot swapping, the MAX5950 circuitbreaker function is enabled. To disable sensing inputcurrent, remove resistor R7 and install a 0Ω, 0805, sur-face-mount resistor at the R6 resistor pads.

PWM UVLO Configuration (PUVLO)The MAX5950 and MAX5951 PWM UVLOs are config-ured for 7V (typ) on the rising 12VHS input voltage. OtherPWM UVLOs can be evaluated by selecting andinstalling resistors R4 and R5 for U1, resistors R44 andR45 for U41, or resistors R84 and R85 for U81 (0805case). Using the desired startup voltage, calculate theappropriate resistor value using the following equation:

R R RVIN

VkSTARTUP4 44 84

1 221 10, ,

.= −⎛⎝⎜

⎞⎠⎟ × Ω

RVIN

VRSTARTUP2

1 221 3= −

⎛⎝⎜

⎞⎠⎟ ×

.


6 _______________________________________________________________________________________

PGI

DCEN0

DCENI1

DCENI2

DCENI3

STARTUP1

START

START

STARTUP2

STARTUP3

PGOOD1

PGOOD2

PGOOD3

THRESH1

THRESH2

THRESH3

DCEN0

DCENI1

DCENI2

DCENI3

STARTUP1

STARTUP2

STARTUP3

PGI

PGOOD1

PGOOD2

PGOOD3

THRESH1

THRESH2

THRESH3

TRACKING STARTUP SEQUENCING PGOOD SEQUENCING

DCEN0

START

DCENI1

DCENI2

DCENI3

STARTUP1

STARTUP2

STARTUP3

THRESH1VREG2

VREG1

THRESH2

THRESH3

VREG3

0Ω

Chart 1. Startup Modes Connections

where VINSTARTUP is the desired converter startup volt-age (≥ 7V) and resistors R5, R45, and R85 are 10kΩ.Refer to the MAX5950 data sheet for additional informa-tion on the MAX5950 and MAX5951 PUVLO pin.

DC-DC Enable Input Configuration (THRESH)The MAX5950 and MAX5951 DC-DC enable THRESHinputs are configured for 1.22V by default, and therespective converter starts when its DCENI input isgreater than 1.22V. To evaluate other DCENI startupvoltages, set the THRESH voltage using the equationbelow. Reconfigure the respective controller byinstalling the recommended 0805 surface-mount 1%resistors at the designated resistor PC board pads.Refer to the MAX5950 data sheet for additional informa-tion on the MAX5950 and MAX5951 IC’s THRESH pin.

where VTHRESH is between 0.6V and 2.5V.

Output Voltage Sensing (SENSE)The MAX5950 and MAX5951 controllers monitor therespective output voltages to determine if the outputpower is good. Resistors R18 and R19 for U1, resistorsR58 and R59 for U41, and resistors R98 and R99 (0805case) for U81 are selected to provide a PGOOD trip volt-age that is 90% of the typical output voltage. To evaluateother PGOOD trip voltages, use the following equation:

R19, R59, R99 = 10kΩ

where VPGTH is the desired power-good threshold volt-age. Resistors R19, R59, and R99 are typically 10kΩ.Refer to the MAX5950 data sheet for additional informa-tion on the MAX5950 and MAX5951 SENSE pins.

Current-Limiting (ILIM)All three outputs on the MAX5950 EV kit are configuredfor lossless valley current sensing by default. Refer tothe MAX5950 IC data sheet for more information onhow lossless valley current limiting functions and howto set the required ILIM resistors, R22, R62, and R102.Alternatively, output 1 can be independently reconfig-ured to use a current-sense resistor. To reconfigure thecurrent-sensing method, see Table 2; use the equa-tions below for selecting the current-sense resistor.

The MAX5950 controller turns off the switching MOSFET(N2-A) for the subsequent switching cycle if the voltagedifference at CS+ and CS- reached 100mV during theoff-time for more than 8 sequential clock cycles, thecontroller will go into hiccup mode. Current-senseresistor R13 sets the valley current limit when using thismode of current sensing. To evaluate other current lim-its, current-sense resistor R13 must be replaced with asurface-mount resistor (1210 size) as determined bythe following equation:

where VCS = VILIM/10, IOUTMAX = maximum DC outputcurrent (2.5A as configured).

When using a current-sense resistor, use R21 and R22 toset the ILIM threshold voltage. Use the following equa-tion to configure the desired ILIM threshold voltage.

where VREG = 5V, VILIM is in the range of 0.5V to 3.5V,and R22 is 5kΩ.

Refer to the MAX5950 data sheet for additional informationon the MAX5950 controller current-sensing capabilities.

RV

VRREG

ILIM21

101 22=

×−

⎛

⎝⎜

⎞

⎠⎟ ×

R V ICS OUTMAX13 = /

R R RV

VkPGTH18 58 98

0 81 10, ,

.= −⎛⎝⎜

⎞⎠⎟ × Ω

R R or RV

Vk

THRESH27 67 107

51 10, , = −

⎛

⎝⎜

⎞

⎠⎟ × Ω

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IC SENSE RESISTOR RESISTORS ILIM RESISTORS EV KIT FUNCTION

R13 = PC trace shortR11 = 0Ω

R12 = OpenR21 = OpenR22 = 5kΩ

Lossless current sensing

U1R13 = Cut open trace

shorting pads, calculateR11 = Open

R12 = 0ΩR21 = CalculateR22 = 48.7kΩ

Alternate inductor valleycurrent sensing

Table 2. Current-Limiting Reconfiguration

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51 MAX5950PB Power Board Assembly

X8E PCIe Power Board AssemblyThe MAX5950PB PCIe power board assembly includesbulk-holdup capacitance for the PCIe 12V and 3.3Vauxiliary power rails. Connect a 12V, 2A minimum ratedpower supply to the +12V and adjacent PGND bananajacks or pads. Connect a 3.3V, 1A minimum ratedpower supply to the +VAUX and adjacent PGNDbanana jacks or pads. Yellow LEDs D1 and D2 on thepower board indicate when power is applied and assistdischarging the respective bulk-holdup capacitance.The MAX5950PB provides power to a single X8E PCIeconnector, J1.

The MAX5950PB includes three switches, HC logic,and LEDs that facilitate the simulation of hot swapping

a MAX5950 EV kit into a server’s backplane. Slideswitch SW1 controls the PWRLED signal and SW2 con-trols the ATNLED signal. SW3 is used to enable/disableor reset the MAX5950 controller, thus enabling and dis-abling the MAX5950 EV kit outputs.

Red LED D3 indicates when a PWRFLT signal is acti-vated and/or the green LED D4 indicates when aMPWRGD signal is activated by the MAX5950 con-troller. The green LED D5 indicates when a PRSNT andATNLED signal are present, thus simulating a systemslot interface signal.

See the Quick Start section for additional informationon configuring and using the MAX5950PB powerboard assembly.


8 _______________________________________________________________________________________

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PCI-Express-X8E Hot-Swap DC-DC Converters

+3.3VAUX

R17.5Ω

C1100µF

PGND

HSENSE

R6OPEN

+12VIN

+12VIN

R2OPEN

R3OPEN

GND1PWREN

PWRFLT

MPWRGD

PGNDVREG1

R27OPEN

R280Ω

GND1

+12VHSR4

OPEN

R5OPEN

GND1

R25110Ω

R26110Ω

D2YELLOW

D1GREEN

PWRLED

ATNLED

PGND GND1

GND1

PGOOD3 PGOOD1 DCENI1 DCENO STARTUP GND1

SYNCIN2

R240Ω

GND1

GND1

R21OPEN

VREG1

C140.033µF

R202.15kΩ

1%C13

220pF

PGNDPGND

GND1

R1915kΩ1%

GND1

R1620kΩ0.5%

C12820pF

C1122µF6.3V

C1022µF6.3V

CS-1

R12OPEN

R13SHORT(PC TRACE)

N2-B

GND1

VOUT11.2V, 2.5A

VOUT1

C91000pF

R14576Ω

1%

R1510kΩ0.5%

R185.23kΩ1%

R2248.7kΩ1%

R2349.9kΩ1%

R1010Ω

C81µF16V

+12VHS

7 8

N2-ATP22

130

29

25

R110Ω

5 6

4

3

CS-127

TP3

L11µH

3128321

C72.2µF10V

R85.6Ω

D4

C51µF16V

C422µF

16V

C322µF

16V

HSENSE

+12VHS

R70Ω

+12VHS

345

1, 3

TP1

2, 5N14, 6

C20.001µF

50V

B9

B11

B10

B49

B48

B47

B3

B2

B1

VREG1

C62.2µF10V

GND1

B12

A8

A9

B14

A12

A11

A49

A48

A47

A3

A2

A1

A5

A6

6

7

8

9

13

2

10 19 12 11 18 14 16 15 17 23 22

PGI PGOOD DCENI DCENO STARTUP AGND SYNCIN SYNCOUT RT ILIM SENSE

20

21

26

24

COMP

FB

PGND

CS+

DL

CS-

LX

DHIN GATE HSENSE PWM_IN REG DREG BST

PUVLO

THRESH

MPWRGD

PWRFLT

PWREN

HUVLO

MAX5950

U1

56

N3

43

12

PGOOD1

R9910Ω

D3GREEN

+12VHS

Figure 1. MAX5950 EV Kit Schematic—Hot-Swap and VOUT1 Circuits

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10 ______________________________________________________________________________________

VREG

2

GND2

GND2

GND2

GND2

GND2

GND2

GND2

PGND

PGND

GND2

GND2

DCEN

I2DC

ENI

GND2

PUVL

O

THRE

SHAGND

PGOOD

SYNCIN

RT

SYNCOUT

SENSE

ILIM

STAR

TUP

STAR

TUP

PGOO

D2

SYNC

IN2

+12V

HS

+12V

HS+1

2VHS

+12V

HS

VOUT

2

VOUT

2

N43

2.5V

, 1.2

5A

D44

R67

OPEN

R64

OPEN

R60

3.83

kΩ1%

R48

5.6Ω

C54

0.03

3µF

C53

220p

F

R63

59.0

kΩ1%

R62

34kΩ

1%

R59

15kΩ

1%

R45

OPEN

R44

OPEN

R50

OPEN L41

6.8u

H

R49

910Ω

D43

GREE

N

C49

OPEN

C46

2.2µ

F10

VC4

51µ

F16

V

C47

2.2µ

F10

V

C48

1µF

16V

C44

10µ

F16

V

C50

22µ

F6.

3VR5

413

3Ω 1%

R55

10kΩ

0.5%

R56

4.70

kΩ0.

5%

R57

10Ω

1%

R58

27.4

kΩ1%

C52

1500

pFR6

80Ω

1419

1617

1523

22

2021262427

1

2

78

4

3

25

16

3

4

56 N4

2-B

N42-

A

TP4

TP5

252930

13 2 12 18

DH LX CS-

DL CS+

PGND FB

COM

P

3

N.C.

N.C.

N.C.

N.C.

N.C.N.C.

N.C.

N.C.

IN

IN

REG

DREG

BST

46

78

910

111

532

2831

U41

MAX

5951

Figure 2. MAX5950 EV Kit Schematic—VOUT2 Circuit

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VREG

3

GND3

GND3

GND3

GND3

GND3

GND3

GND3

PGND

PGND

GND3

GND3

DCEN

I3DC

ENI

GND3

PUVL

O

THRE

SHAGND

PGOOD

SYNCIN

RT

SYNCOUT

SENSE

ILIM

STAR

TUP

STAR

TUP

PGOO

D3 SYNC

IN2

+12V

HS

+12V

HS+1

2VHS

D83

GREE

N

R89

110Ω

VOUT

3

VOUT

3

3.3V

, 1.2

5A

D84

R107

OPEN

R104

OPEN

R100

3.83

kΩ1%

R88

5.6Ω

C94

0.03

3µF

C93

220p

F

R103

59.0

kΩ1%

R102

34kΩ

1%

R99

15kΩ

1%

R85

OPEN

R84

OPEN

R90

OPEN L81

10µ

H

C89

OPEN

C86

2.2µ

F10

VC8

51µ

F16

V

C87

2.2µ

F10

V

C88

1µF

16V

C84

10µ

F16

V

C90

22µ

F6.

3VR9

413

3Ω 1%

R95

10kΩ

0.5%

R96

3.16

kΩ0.

5%

R97

39.2Ω

1%

R98

40.2

kΩ1%

C92

1500

pFR1

08 0Ω

1419

1617

1523

22

2021262427

1

2

78

3

4

56 N8

2-B

N82-

A

TP6

TP7

252930

13 2 12 18

DH LX CS-

DL CS+

PGND FB

COM

P

3N.C.

N.C.

N.C.

N.C.

N.C.N.C.

N.C.

N.C.

IN

IN

REG

DREG

BST

46

78

910

111

532

28

U81

31

MAX

5951

Figure 3. MAX5950 EV Kit Schematic—VOUT3 Circuit

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12 ______________________________________________________________________________________

Figure 4. MAX5950 EV Kit Schematic—Tracking SequencingConfiguration Circuit

PGOOD3(PGI)

PGOOD2

PGOOD1

R30OPEN

R31OPEN

R320Ω

DCENI2R340Ω

DCENI3

DCENI1

DCENO

STARTUP

R39OPEN

C15OPEN

R380Ω

R370Ω

R360PEN

R350PEN

R330PEN

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Figure 5. MAX5950 EV Kit Component Placement Guide—Component Side

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Figure 6. MAX5950 EV Kit PC Board Layout—Component Side

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Figure 7. MAX5950 EV Kit PC Board Layout—Inner Layer, GND/PGND Ground Plane

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16 ______________________________________________________________________________________

Figure 8. MAX5950 EV Kit PC Board Layout—Inner Layer, VCC/PGND Power Plane

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Figure 9. MAX5950 EV Kit PC Board Layout—Solder Side

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Figure 10. MAX5950 EV Kit Component Placement Guide—Solder Side

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Figure 11. MAX5950PB Schematic

3SW

1

2+V

AUX

3SW

2

2

+VAU

X

+VAU

X

+VAU

X

+VAU

X

TP1

TP2

ATNL

ED TP5

PRSN

TTP3

TP4

TP6

2

R3 620Ω R4 620Ω R5 10kΩ

1

D4GR

EEN

D3 RED

21

PWRE

N

C1 150µ

FC2 1µ

F

C9 1µF

C8 1µF

C7 680µ

FC6 68

0µF

C5 680µ

FC4 68

0µF

C3 680µ

F

+12V

+12V

+12V

R2 510Ω

D2 YELL

OW

D1 YELL

OW

PGND

PGND

PGND

PGND

+VAU

X

+VAU

X

+VAU

X

R1 62Ω

1212

PWRL

ED

R810

0kΩ

J1X8

E PC

Ie

+12V

+12V

+12V

RSVD

ATNS

WM

RST

SMDA

TSM

CLK

+VAU

XPGN

D+V

AUX

PWRE

NRS

VDGN

D

GND

GND

PETP

0PE

TN0

PETN

1

PETN

2

PETN

3

PETN

4

PETP

1

PETP

2

PETP

3

PETP

4

PETN

5PE

TP5

PETN

6PE

TP6

PETN

7PE

TP7

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

GND

RSVD

+12V

+12V

+12V

SRPO

SRNO

SRP1

SRN1

SRP2

SRN2

SRP3

SRN3

STOR

_SB-

1ST

OR_S

B-1

RSVD

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10

B11

B12

B13

B14

B15

B16

B17

B18

B19

B20

B21

B22

B23

B24

B25

B26

B27

B28

B29

B30

B31

B32

B33

B34

B35

B36

B37

B38

B39

B40

B41

B42

B43

B44

B45

B46

B47

B48

B49

B50

B51

B52

B53

B54

B55

B56

B57

B58

B59

B60

B61

B62

B63

B64

B65

B66

B67

B68

B69

B70

GND

GND

GND

RSVD

PWRL

EDAT

NLED

SMBA

LERT

PWRF

LTM

PWRG

DW

AKE

PRSN

TGN

D

GND

GND

GND

GND

GND

GND

REFC

LK+

REFC

LK-

PERP

0PE

RN0

PERP

1PE

RN1

PERP

2PE

RN2

GND

GND

PERP

3PE

RN3

GND

GND

PERP

4PE

RN4

GND

GND

PERP

5PE

RN5

GND

GND

PERP

6PE

RN6

GND

GND

GND

GND

GND

GND

GND

GND

GND

PERP

7PE

RN7

RSVD

STP0

STN0

GND

GND

GND

GND

RSVD

RSVDGN

D

STP0

STN0

STOR

_SB-

3ST

OR_S

B-4

STP2

STN2

STP3

STN3

A15

A16

A17

A18

A19

A20

A21

A22

A23

A24

A25

A26

A27

A28

A29

A30

A31

A32

A33

A34

A35

A36

A37

A38

A39

A40

A41

A42

A43

A44

A45

A46

A47

A48

A49

A50

A51

A52

A53

A54

A55

A56

A57

A58

A59

A60

A61

A62

A63

A64

A65

A66

A67

A68

A69

A70

A1 A2 A3 A4 A5 A6 A7 A8 A9 A10

A11

A12

A13

A14

+12V

+VAU

X

U1-A

PWRL

ED

ATNL

ED

1 2

7

3

R710

0kΩ

1A 1B

14 VCC

GND

1Y

R6 150Ω

21

D5GR

EEN

PWRL

ED

ATNL

ED

4 52A 2B

2Y

PWRL

ED

ATNL

ED

9 103A 3B

3Y

PWRL

ED

ATNL

ED

12 134A 4B

4Y

1 1

3SW

32

TP7

1

PWRE

N

PRSN

TPW

REN

11U1

-D

U1-C

U1-B 86

MAX5950PB Power Board Assembly

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20 ______________________________________________________________________________________

Figure 12. MAX5950PB Component Placement Guide—Component Side

Figure 13. MAX5950PB PC Board Layout—Component Side

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Figure 14. MAX5950PB PC Board Layout—Solder Side

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22 ______________________________________________________________________________________

Appendix A

1 2 3 4 5 6 7 8

24

N2 Si72

12DN

TP8

PGND

GND

1.2V

, 2.5

A

VOUT

1VO

UT1

61 2 3

N3 FDG3

11N_

NL

STAR

TUP

SYNC

5 4

TP7

D4 GRN

L1 1µH

23 22 21 20 19 18 17

3231

3087

65

12

34

2928

2726

25

REG

BST

DH

LX

DVREG

DL

PGND

CS-

109

1112

1314

1516

0

PG1

MPWRGD

DCEND

DCENI

THRESH

GND

SYNCOUT

SYNCIN

EP

+12V

O

PUVL

O

HSEN

SE

GATE

+12V

IN+1

2VIN

HUVL

O

PWRE

N

PWRF

LT

CS+

D3VR

EG1

C4 2.2µ

F

C8 1µF

C9 1nF

R5 10Ω

R2 110Ω R3 110Ω

R4 5.6Ω

R14

49.9

kΩ

C3 2.2µ

F

LIM

SENS

E FB

COM

P

PGOO

D

STAR

TUP RT

R11

20.0

kΩ0.

5%

R13

15.0

kΩ

R95.

23kΩ

R15

910Ω

R6 576Ω

R8 2150Ω

R10

48.7

kΩ

R7 10.0

kΩ0.

5%

R1 7.5Ω C1 10

0µF

6.3V

PCI E

XP P

LUG

P1

TP1

+12V

IN

TP5 PG

ND

TP9

D1 GRN

D2 YEL

A01

B01

A02

B02

A03

B03

A04

B04

A05

B05

A06

B06

A07

B07

A08

B08

A09

B09

A10

B10

A11

B11

A12

B12

A13

B13

A14

B14

A47

B47

A48

B48

A49

B49

U1

MAX

5950

C11

22µ

F

C13

33nF

C14

220p

F

C12

820p

F

C10

47µ

F

N1Si

3948

DV-E

3

53

2

46

1

PWRF

LT

C7 1µF

C622

µF

C522

µF

C2 1nF

1 2 3 4 5 6 7 8

24

N22

TP11

PGND

2.5V

, 1.2

5A

VOUT

2TP

10VO

UT2

61 2 3

N23

FDG3

11N_

NL

5 4

D24

GRN

L21

6.8µ

H

23 22 21 20 19 18 17

32

31

30

87

65

12

34

29

28

27

26

25

REG

BST

DH

LX

DVREG

DL

PGND

CS-

10

9

11

12

13

14

15

16

0

N.C.

N.C.

N.C.

DCENI

THRESH

GND

SYNCOUT

SYNCIN

EP

+12M

N

PLM

D

N.C.

N.C.

+12V

IN

N.C.

N.C.

N.C.

CS+

D23

VREG

2

C24

2.2µ

F

C28

1µF

C29

1nF

R25

10Ω

R24

5.6Ω

R34

59.0

kΩ

C23

2.2µ

F

LIM

SENS

E FB

COM

P

PGOO

D

STAR

TUP RT

R32

10.0Ω

R31

4.70

kΩ0.

5%

R33

15.0

kΩ

R29

27.4

kΩ

R35

910Ω

R26

133Ω

R28

3830Ω

R30

34.0

kΩ

R27

10kΩ

0.5%

U21

MAX

5951

C33

33nF

C34

220p

F

C32

1.5n

F

C30

22µ

F

C27

1µF

C26

10µ

F

1 2 3 4 5 6 7 8

24

N42

TP13

PGND

3.3V

, 1.2

5AVO

UT3

TP12

VOUT

3

D44

GRN

L41

10µ

H

23 22 21 20 19 18 17

32

31

30

87

65

12

34

29

28

27

26

25

REG

BST

DH

LX

DVREG

DL

PGND

CS-

10

9

11

12

13

14

15

16

0

N.C.

N.C.

N.C.

DCENI

THRESH

GND

SYNCOUT

SYNCIN

EP

+12V

IN

PUVL

O

N.C.

N.C.

+12V

IN

N.C.

N.C.

N.C.

CS+

D43

VREG

3

C44

2.2µ

F

C48

1µF

C49

1nF

R45

10Ω

R44

5.6Ω

R54

59.0

kΩ

C43

2.2µ

F

LIM

SENS

E FB

COM

P

PGOO

D

STAR

TUP RT

R52

39.2Ω

R51

3.16Ω

0.5%

R53

15.0

kΩ

R49

40.2

kΩ0.

5%

R56

110Ω

R46

133Ω

R48

3830Ω

R50

34.0

kΩ

R47

10kΩ

0.5%

U41

MAX

5951

C53

330F

C54

220p

F

C52

1.5n

F

C50

22µ

F

TP3

PWRF

LT

TP4

MPW

RGD

TP2

PWRE

N

C47

1µF

C46

10µ

F

TP6

+12V

HS

MPW

RGD

PWRE

N

Figure 15. MAX5950 EV PCIe ExpressModule Reference Design

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Figure 16. MAX5950 EV PCIe ExpressModule Reference Design—Composite View

Figure 17. MAX5950 EV PCIe ExpressModule Reference Design—Top Layer

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Figure 19. MAX5950 EV PCIe ExpressModule Reference Design—Top Silkscreen

Figure 18. MAX5950 EV PCIe ExpressModule Reference Design—Bottom Layer

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PGND

+12VHS

12VIN

Figure 20. MAX5950 EV PCIe ExpressModule Reference Design—Bottom Silkscreen

Figure 17. MAX5950 EV PCIe ExpressModule Reference Design—Inner 12VIN-12VHS-PGND Layer

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Boblet

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses areimplied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

26 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products. Inc.

BobletBoblet

GND PGND

Boblet

Figure 22. MAX5950 EV PCIe ExpressModule Reference Design—Inner GND-PGNDLayer

max5950 ev kit - maxim integrated · pdf filemax5950 ev kit also includes connections for the...

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