Datasheet

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General Description

The MAX5946 dual hot-plug controller is designed for

PCI Express™ applications. The device provides hot-

plug control for 12V, 3.3V, and 3.3V auxiliary supplies of

two PCI express slots. The MAX5946’s logic inputs/out-

puts allow interfacing directly with the system hot-plug

management controller or through an SMBus™ with an

external I/O expander. An integrated debounced atten-

tion switch and present-detect signals are included to

simplify system design.

The MAX5946 drives four external n-channel MOSFETs

to control the 12V and 3.3V main outputs. The 3.3V aux-

iliary outputs are controlled through internal 0.3Ω

n-channel MOSFETs. Internal charge pumps provide

gate drive for the 12V outputs while the gate drive of

the 3.3V output is driven by the 12V input supply. The

3.3V auxiliary outputs are completely independent from

the main outputs with their own charge pumps.

At power-up, the MAX5946 keeps all of the external

MOSFETs off until the supplies rise above their respec-

tive undervoltage lockout (UVLO) thresholds. The

device keeps the internal MOSFETs off only until the

auxiliary input supply rises above its UVLO threshold.

Upon a turn-on command, the MAX5946 enhances the

external and internal MOSFETs slowly with a constant

gate current to limit the power-supply inrush current.

The MAX5946 actively limits the current of all outputs at

all times and shuts down if an overcurrent condition

persists for longer than a programmable overcurrent

timeout. Thermal-protection circuitry also shuts down all

outputs if the die temperature exceeds +150°C. After an

overcurrent or overtemperature fault condition, the

MAX5946L latches off while the MAX5946A automatical-

ly restarts after a restart time delay. The device is avail-

able in a 36-pin (6mm × 6mm) thin QFN package and

operates over the -40°C to +85°C temperature range.

Applications

Servers

Desktop Mobile Server Platforms

Workstations

Embedded Devices

Features

♦ PCI Express Compliant

♦ Hot Swaps 12V, 3.3V, and 3.3V Auxiliary for 2

PCI-E Slots

♦ Integrated Power MOSFET for Auxiliary Supply

Rails

♦ Controls dI/dt and dV/dt

♦ Active Current Limiting Protects Against

Overcurrent/Short-Circuit Conditions

♦ Programmable Current-Limit Timeout

♦ PWRGD Signal Outputs with Programmable

Power-On Reset (POR) (160ms Default)

♦ Latched FAULT Signal Output after Overcurrent

or Overtemperature Fault

♦ Attention Switch Inputs/Outputs with 4ms

Debounce

♦ Present-Detect Inputs

♦ Forced-On Inputs Facilitates Testing

♦ Thermal Shutdown

♦ Allows Control through SMBus with an I/O

Expander

MAX5946

Dual PCI Express, Hot-Plug

Controller

________________________________________________________________ Maxim Integrated Products 1

19-3483; Rev 0; 11/04

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.

EVALUATION KIT

AVAILABLE

ONB

AUXONB

12SB+

12GB

3.3SB+

3.3SB-

PRES-DETB

3.3VAUXIN

3.3VAUXOB

PWRGDB

3.3GB

3.3VAUXOA

PWRGDA

FAULTA

3.3GA

PGND

GND

12VIN

INPUT1

OUTPUT1

OUTPUT2

INPUT2

TIM

PORADJ

THIN QFN

MAX5946

TOP VIEW

12SB-

FAULTB

FONB

ONA

AUXONA

12SA+

12GA

3.3SA+

3.3SA-

PRES-DETA

12SA-

FONA

36 35 34 33 32 31

30 29 28

10 11 12

13 14 15 16 17 18

Pin Configuration

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX5946AETX

-40°C to +85°C 36 Thin QFN

MAX5946LETX

-40°C to +85°C 36 Thin QFN

Typical Application Circuit appears at end of data sheet.

SMBus is a trademark of Intel Corp.

PCI Express is a trademark of PCI-SIG Corp.

Summary of content (23 pages)

PAGE 1
9-3483; Rev 0; 11/04 KIT ATION EVALU LE B A IL A AV Dual PCI Express, Hot-Plug Controller ♦ PCI Express Compliant ♦ Hot Swaps 12V, 3.3V, and 3.
PAGE 2
MAX5946 Dual PCI Express, Hot-Plug Controller ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND, unless otherwise noted.) 12VIN......................................................................-0.3V to +14V 12GA, 12GB ..............................................-0.3V to (V12VIN + 6V) 12SA+, 12SA-, 12SB+, 12SB-, 3.3GA, 3.3GB .....................................-0.3V to (V12VIN + 0.3V) 3.3VAUXIN, ONA, ONB, FAULTA, FAULTB ............-0.3V to +6V PWRGDA, PWRGDB ..................................
PAGE 3
Dual PCI Express, Hot-Plug Controller (V12VIN = V12S_- = V12S_+ = 12V, V3.3S_+ = V3.3S_- = V3.3VAUXIN = VON_ = VAUXON_ = VFON__ = 3.3V, PWRGD_ = FAULT_ = PORADJ = TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 17 20 23 mV 3.3V CONTROL 3.3V Current-Limit Threshold (V3.3S_+ - V3.3S_-) V3.3ILIM 3.3G_ Gate Charge Current I3.3G_CHG V3.
PAGE 4
MAX5946 Dual PCI Express, Hot-Plug Controller ELECTRICAL CHARACTERISTICS (continued) (V12VIN = V12S_- = V12S_+ = 12V, V3.3S_+ = V3.3S_- = V3.3VAUXIN = VON_ = VAUXON_ = VFON__ = 3.3V, PWRGD_ = FAULT_ = PORADJ = TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
Dual PCI Express, Hot-Plug Controller (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical Application Circuit.) 1.4 1.2 1.0 0.8 0.6 10 35 60 1.8 1.7 1.6 ON_ OR AUXON_ 1.5 1.4 1.3 0.4 1.2 0.2 1.1 85 MAX5946 toc03 1.9 THRESHOLD VOLTAGE (V) 1.6 SUPPLY CURRENT (mA) -15 1.
PAGE 6
Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical Application Circuit.) 12VIN UNDERVOLTAGE LOCKOUT THRESHOLD vs. TEMPERATURE 3.3VAUXIN UNDERVOLTAGE LOCKOUT THRESHOLD vs. TEMPERATURE 10.15 MAX5946 toc11 2.70 MAX5946 toc10 10.20 2.68 10.
PAGE 7
Dual PCI Express, Hot-Plug Controller TURN-ON DELAY 3.3V OUTPUT AND 3.3V AUXILIARY OUTPUT 3.3V INPUT/3.3V AUXILIARY INPUT POWER-UP MAX5946 toc17 MAX5946 toc16 3.3G_ 10V/div 5V/div 3.3VAUXO_ OUTPUT VOLTAGE 3.3V OUTPUT 5V/div 5V/div 3.3 INPUT, 3.3VAUXIN 3.3S_+ 5V/div 5V/div 3.3 OUTPUT VOLTAGE 3.3VAUXO_ 5V/div 5V/div PWRGD 3.3G_ 10V/div PWRGD_ 5V/div 100ms/div 4ms/div FAULT CONDITION ON 12V OUTPUT (AUTORESTART OPTION MAX5946A) FAULT CONDITION ON 3.
PAGE 8
MAX5946 Dual PCI Express, Hot-Plug Controller Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical Application Circuit.) FAULT CONDITION ON 3.3V OUTPUT (LATCH OPTION MAX5946L) FAULT CONDITION ON 12V OUTPUT MAX5946 toc23 MAX5946 toc22 tFAULT RLOAD STEP TO 1.
PAGE 9
Dual PCI Express, Hot-Plug Controller SHORT CIRCUIT ON 12V OUTPUT SHORT CIRCUIT ON 3.3V OUTPUT MAX5946 toc28 MAX5946 toc29 3.3V OUTPUT CURRENT 2A/div 12V OUTPUT CURRENT 25A/div 12G_ 20V/div 0V 12V OUTPUT VOLTAGE 10V/div 0V 3.3G_ 5V/div 3.3V OUTPUT VOLTAGE 5V/div FAULT_ 5V/div 0V 4µs/div FAULT_ 5V/div 2ms/div SHORT CIRCUIT ON 3.3AUXO_ SHORT CIRCUIT ON 3.3V OUTPUT MAX5946 toc31 MAX5946 toc30 3.3VAUXO_ OUTPUT CURRENT 500mA/div 3.3V OUTPUT CURRENT 10A/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div 3.
PAGE 10
MAX5946 Dual PCI Express, Hot-Plug Controller Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical Application Circuit.) POWER-UP INTO FAULT (3.3V MAIN) POWER-UP INTO FAULT (12V OUTPUT) MAX5946 toc34 MAX5946 toc35 RLOAD = 0.5Ω 3.
PAGE 11
Dual PCI Express, Hot-Plug Controller POWER-ON-RESET TIME vs. PORADJ RESISTOR DEBOUNCED ON/OFF OPERATION tPOR_HL (ms) INPUT_ 2V/div OUTPUT_ 2V/div 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 MAX5946 toc41 MAX5946 toc40 0 100 200 300 400 500 600 700 800 900 1000 10ms/div RPORADJ (kΩ) tFAULT TIME DELAY vs.
PAGE 12
Dual PCI Express, Hot-Plug Controller MAX5946 Pin Description PIN 12 NAME FUNCTION Present-Detect Input A. PRES-DETA accepts inputs from the PRSNT#2 pin on a PCI express connector. PRES-DETA has an internal pullup to 3.3VAUXIN. When PRES-DETA is low, the outputs follow the command from ONA and AUXONA after a 4ms debounced time. When PRES-DETA goes from low to high, all outputs of the respective slot shut down with no delay (see Table 2). 1 PRES-DETA 2 FONA Forced-On Input A.
PAGE 13
Dual PCI Express, Hot-Plug Controller PIN NAME FUNCTION 19 3.3SB- Slot B 3.3V Negative Current-Sense Input. See 3.3SA- function. 20 3.3SB+ Slot B 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to 3.3SB+ using the Kelvin-sensing technique to assure accurate current sensing. 21 12GB Slot B 12V Gate-Drive Output. See 12GA function. 22 12SB- Slot B 12V Negative Current-Sense Input. See 12SA- function. 23 12SB+ Slot B 12V Positive Current-Sense Input.
PAGE 14
MAX5946 Dual PCI Express, Hot-Plug Controller RTIM RPORADJ INPUT1 INPUT2 OUTPUT1 PWRGDA FAULTA 12VIN OUTPUT2 PORADJ TIM PWRGDB FAULTB 12SB+ 12SA+ RSENSE12A 54mV + - + - 500mV 500mV CHARGE PUMP 12SA- + - + - 54mV RSENSE12B CHARGE PUMP 12SB5µA 5µA 12GA 10µA 150µA 12GB Aµ01 10µA tFAULT OSCILLATOR DEBOUNCE tPOR OSCILLATOR FAST OSCILLATOR A µ0 0 1 100mA 100mA 150µA MAX5946 3.3SA+ 3.3SB+ 100mV RSENSE3.3A 20mV + - + - + - 100mV + - RSENSE3.3B 20mV 3.3SA- 3.
PAGE 15
Dual PCI Express, Hot-Plug Controller MAX5946 Table 1. Power Requirements for PCI Express Connectors POWER RAIL X1 CONNECTOR X4/8 CONNECTOR X16 CONNECTOR Voltage Tolerance ±9% (max) ±9% (max) ±9% (max) Supply Current 3.0A (max) 3.0A (max) 3.0A (max) 1000µF (max) 1000µF (max) 1000µF (max) Voltage Tolerance ±8% (max) ±8% (max) ±8% (max) Supply Current 0.5A (max) 2.1A (max) 5.
PAGE 16
MAX5946 Dual PCI Express, Hot-Plug Controller ON_ ON_, AUXON_ VON_,TH VPGTH12 VPGTH3.3 12G_, 3.3G_ VON_,TH 12VO_, 3.3VO_ V12ILIM,TH RSENSE 12G_ 12V OUTPUT CURRENT 3.3VAUXO_ 3.3VAUXO_ VPGTH3.3AUX PWRGD_ tPOR_HL PWRGD_ 3.3AUXIN RISING EDGE FAULT_ 3.3VAUXIN RISING EDGE 2 x tFAULT FAULT_ PWRGD_ IS PULLED UP TO 3.3VAUXO_. FAULT_ IS PULLED UP TO 3.3VAUXIN. A FAULT ON THE 3.3V OUTPUT OR 3.3VAUXO_ OUTPUT PRODUCES SIMILAR RESULTS. PWRGD_ IS PULLED UP TO 3.3. FAULT_ IS PULLED UP TO 3.3AUXIN.
PAGE 17
Dual PCI Express, Hot-Plug Controller • A fault on a main output (12V or 3.3V) shuts down both main outputs of the respective slot. The 3.3V auxiliary is not affected. • A fault on the 3.3V auxiliary output shuts down all three outputs of the respective slot. The MAX5946A automatically restarts from a fault shutdown after the tRESTART period, while the MAX5946L latches off.
PAGE 18
MAX5946 Dual PCI Express, Hot-Plug Controller SHUT DOWN 12V AND 3.3V OUTPUTS. ASSERT FAULT_ STAY WAITING FOR tRESTART Y HAS tFAULT ELAPSED? WAS CURRENT LIMIT DETECTED ON ANY 12V OR 3.3V OUTPUT? Y START COUNTING tFAULT 12V AND 3.3V OUTPUTS ARE ENABLED N N IS FAULT STILL PRESENT? Y N RESET tFAULT COUNTER Y N LATCH-OFF OPTION? RESET FAULT_ AND RESTART 12V, 3.3V SUPPLIES STAY WAITING FOR ON_ TRANSITION HIGH->LOW->HIGH N ENABLE CHARGE ON 12G_ AND 3.3G_ PINS.
PAGE 19
Dual PCI Express, Hot-Plug Controller The gate drive for the external MOSFETs is provided at 12GA, 12GB, 3.3GA, and 3.3GB. 12G_ is the gate drive for the 12V main supply and is boosted to 5.3V above V12VIN by an internal charge pump. During turn-on, 12G_ sources 5µA into the external gate capacitance to control the turn-on time of the external MOSFET. During turn-off, 12G_ sinks 150µA from the external gate capacitance to quickly turn off the external MOSFET.
PAGE 20
MAX5946 Dual PCI Express, Hot-Plug Controller Table 3. Component Manufacturers COMPONENT MANUFACTURER PHONE Vishay-Dale 402-564-3131 www.vishay.com IRC 704-264-8861 www.irctt.com Sense Resistor MOSFETs WEBSITE Fairchild 888-522-5372 www.fairchildsemi.com International Rectifier 310-322-3331 www.irf.com Motorola 602-244-3576 www.mot-sps.com/ppd/ Vishay-Siliconix — large capacitive loads due to their adjustable startup times and adjustable current-limit thresholds.
PAGE 21
Dual PCI Express, Hot-Plug Controller V12VIN PCI EXPRESS SLOT A PCI EXPRESS SLOT B ADD-IN CARD IN5819 Q1 SI7448DP-T1 PRSNT1 V3.3AUXIN R1 8mΩ Q3 SI7448DP-T1 R3 8mΩ PRSNT1 +12V +12V PWRGD 12GB 12SB+ 12VIN 3.3VAUXIN 12SA+ 12SA- 12GA GND 112SB- 1µF 0.1µF GND PWRGD PWRGDB PWRGDA 10kΩ 10kΩ MAX5946 3.3VAUX 3.3VAUXOA 3.3VAUX 3.3VAUXOB RPORADJ = OPEN 3.3SB- 3.
PAGE 22
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.) 36L,40L, QFN.
PAGE 23
Dual PCI Express, Hot-Plug Controller U 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 23 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.