19-3483; 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 3.3V 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 Ordering Information PART TEMP RANGE PIN-PACKAGE MAX5946AETX -40C to +85C 36 Thin QFN MAX5946LETX -40C to +85C 36 Thin QFN 36 35 34 33 32 31 30 29 28 Applications Servers Desktop Mobile Server Platforms Workstations Embedded Devices 12VIN INPUT1 OUTPUT1 OUTPUT2 INPUT2 TIM TOP VIEW PGND GND Pin Configuration PORADJ The MAX5946 dual hot-plug controller is designed for PCI ExpressTM applications. The device provides hotplug control for 12V, 3.3V, and 3.3V auxiliary supplies of two PCI express slots. The MAX5946's logic inputs/outputs allow interfacing directly with the system hot-plug management controller or through an SMBusTM with an external I/O expander. An integrated debounced attention 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 auxiliary outputs are controlled through internal 0.3 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 respective 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 +150C. After an overcurrent or overtemperature fault condition, the MAX5946L latches off while the MAX5946A automatically restarts after a restart time delay. The device is available in a 36-pin (6mm x 6mm) thin QFN package and operates over the -40C to +85C temperature range. Features PRES-DETA FONA 1 27 2 26 ONA AUXONA 12SA+ 12SA- 3 25 4 24 6 22 12GA 3.3SA+ 3.3SA- 7 21 8 20 9 19 5 23 MAX5946 PRES-DETB FONB ONB AUXONB 12SB+ 12SB12GB 3.3SB+ 3.3SB- SMBus is a trademark of Intel Corp. PCI Express is a trademark of PCI-SIG Corp. 3.3GB FAULTB 3.3GA FAULTA PWRGDA 3.3VAUXOA 3.3VAUXIN 3.3VAUXOB PWRGDB 10 11 12 13 14 15 16 17 18 Typical Application Circuit appears at end of data sheet. THIN QFN ________________________________________________________________ Maxim Integrated Products 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. 1 MAX5946 General Description 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 ................................................-0.3V to +6V PGND ....................................................................-0.3V to +0.3V All Other Pins to GND......................-0.3V to (V3.3VAUXIN + 0.3V) Continuous Power Dissipation (TA = +70C) 36-Pin Thin QFN (derate 26.3mW/C above +70C).....2.105W Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C 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 (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 = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V 12V SUPPLY 12V Supply Voltage Range 12VIN Undervoltage Lockout 12VIN Supply Current V12VIN V12UVLO I12VIN V12VIN rising 10.8 12 13.2 9.5 10 10.5 V Hysteresis 0.1 V12VIN = 13.2V 0.5 1 mA 49 54 59 mV V12G_ = GND 4 5 6 A 12VIN CONTROL 12VIN Current-Limit Threshold (V12S_+ - V12S_-) V12ILIM 12G_ Gate Charge Current I12G_CHG Normal turn-off, ON_ = GND, V12G_ = 2V 50 150 250 A 12G_ Gate Discharge Current I12G_DIS Output short-circuit condition, strong gate pulldown to regulation, V12VIN - V12S_ 1V, V12G_= 5V 50 120 180 mA 12G_ Gate High Voltage (V12G_ - V12VIN) V12G_H I12G_ = 1A 4.8 5.3 5.8 V 12G_ Threshold Voltage For PWRGD_ Assertion (Note 2) VPGTH12 Referred to V12VIN, I12G_ = 1A -3.0 -4 -4.8 V 1 A 20 60 A 3.0 3.3 3.6 V 2.52 2.65 2.78 12S_- Input Bias Current 12S_+ Input Bias Current 3.3V SUPPLY 3.3V Supply Voltage Range Undervoltage Lockout (Note 3) 2 V3.3SA+, V3.3SB+ 3.3SA+ rising Hysteresis 30 _______________________________________________________________________________________ V mV 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 = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (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 V3.3G_ = GND 4 5 6 A ON_ = GND, V3.3G_ = 2V 50 150 250 A 3.3G_ Gate Discharge Current I3.3G_DIS Output short-circuit condition, strong gate pulldown to regulation, V3.3S_+ - V3.3S_ 1V, V3.3G_ = 5V 100 150 220 mA 3.3G_ Gate High Voltage (V3.3G_ - V3.3S_+) V3.3G_H Sourcing 1A 4.5 5.5 6.8 V Referred to V3.3VAUXIN, I3.3G_ = 1A -3.0 -4 -4.5 V 1 A 20 60 A 3.0 3.3 3.6 V 2.52 2.65 2.78 V 3.3G_ Threshold Voltage For PWRGD_ Assertion (Note 2) VPGTH3.3 3.3S_- Input Bias Current 3.3S_+ Input Bias Current 3.3V AUXILIARY SUPPLY 3.3VAUXIN Supply Voltage Range 3.3VAUXIN Undervoltage Lockout V3.3VAUXIN V3.3VAUXUVLO 3.3VAUXIN rising Hysteresis 30 3.3VAUXIN Supply Current V3.3VAUXIN = 3.6V 1.5 3.3VAUXIN to 3.3VAUXO_ Maximum Dropout I3.3VAUXO_ = 375mA 3.3VAUXO_ Current-Limit Threshold 3.3VAUXO_ shorted to GND 3.3VAUXO_ Threshold For PWRGD_ Assertion (V3.3VAUXIN - V3.3VAUXO_) (Note 3) 376 470 VPGTH3.3AUX mV 3 mA 225 mV 564 mA 400 mV 2.0 V LOGIC SIGNALS Input-Logic Threshold (ON_, FON_, AUXON_, PRES-DET_, INPUT_) Rising edge 1.0 25 Hysteresis Input Bias Current (ON_, AUXON_, INPUT_) FON_, PRES-DET_ Internal Pullup ON_, AUXON_ High-to-Low Deglitch Time 25 50 4 mV 1 A 75 k s _______________________________________________________________________________________ 3 MAX5946 ELECTRICAL CHARACTERISTICS (continued) 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 = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER PRES-DET_ High-to-Low Deglitch Time PWRGD_ Power-On Reset Time (Note 2) SYMBOL CONDITIONS MIN TYP MAX UNITS 3 5 7 ms PORADJ = open 90 160 250 RPORADJ = 20k 35 55 75 RPORADJ = 100k 145 265 380 tDEG tPOR_HL RPORADJ = 200k PWRGD_ Low-to-High Deglitch Time PWRGD_, FAULT_ OutputHigh Leakage Current FAULT_ Timeout 570 4 tPOR_LH PWRGD_, FAULT_ Output Low Voltage s Sinking 2mA 0.1 Sinking 30mA 0.7 VPWRGD_ = VFAULT_ = 5.5V tFAULT ms 1 TIM = open 5.5 11 17.0 RTIM = 15k 1.4 2.6 3.8 RTIM = 120k 12 22 32 RTIM = 300k V A ms 59 FAULT_ Timeout During Startup tSU 2 x tFAULT ms Autorestart Delay Time tRESTART 64 x tFAULT ms tRESET 100 s +150 C 20 C Fault Reset Minimum Pulse Width (Note 4) Thermal-Shutdown Threshold TSD TJ rising Thermal-Shutdown Threshold Hysteresis OUTPUT_ Debounce Time tDBC 2.6 OUTPUT_ High Voltage Sourcing 2mA OUTPUT_ Low Voltage Sinking 2mA Note 1: Note 2: Note 3: Note 4: 4 4.4 6.2 V3.3VAUXIN V3.3VAUXIN - 0.3 100% production tested at TA = +25C. Parameters over temperature are guaranteed by design. PWRGD_ asserts a time tPOR_HL after VPGTH12, VPGTH3.3, and VPGTH3.3AUX conditions are met. The UVLO for the 3.3V supply is sensed at 3.3SA+. This is the time that ON_ or AUXON_ must stay low when resetting a fault condition. _______________________________________________________________________________________ 0.4 ms V V 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_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, 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 1.0 -40 -15 10 35 60 -40 85 -15 10 35 60 TEMPERATURE (C) TEMPERATURE (C) TEMPERATURE (C) 3.3VAUXO_ OUTPUT VOLTAGE vs. CURRENT 12G_ AND 3.3G_ GATE CHARGE CURRENT vs. TEMPERATURE 12G_ AND 3.3G_ GATE DISCHARGE CURRENT vs. TEMPERATURE 2.5 2.0 1.5 1.0 0.5 5.25 12G_ 5.20 5.15 5.10 5.05 5.00 3.3G_ 4.95 170 85 MAX5946 toc06 5.30 GATE DISCHARGE CURRENT (A) 3.0 5.35 MAX5946 toc05 MAX5946 toc04 3.5 165 3.3G_ 160 155 12G_ 150 4.90 0 4.85 0 0.1 0.2 0.3 0.4 0.5 0.6 145 -40 -15 10 35 60 85 -40 -15 10 35 60 TEMPERATURE (C) TEMPERATURE (C) 3.3VAUX INTERNAL SWITCH MAXIMUM DROPOUT vs. TEMPERATURE 12V AND 3.3V CURRENT-LIMIT THRESHOLD VOLTAGE vs. TEMPERATURE AUXILIARY CURRENT LIMIT vs. TEMPERATURE 0.12 0.10 0.08 0.06 0.04 0.02 12V CURRENT-SENSE THRESHOLD 40 3.3V CURRENT-SENSE THRESHOLD 30 20 10 -40 -15 10 35 TEMPERATURE (C) 60 85 0.495 0.490 0.485 0.480 0.475 0.470 0.465 0.460 0.455 0 0 85 MAX5946 toc09 50 0.500 AUXILIARY CURRENT LIMIT (A) 0.14 MAX5946 toc08 0.16 60 CURRENT-LIMIT THRESHOLD VOLTAGE (mV) AUXILIARY OUTPUT CURRENT = 375mA 0.18 MAX5946 toc07 OUTPUT CURRENT (A) 0.20 DROPOUT VOLTAGE (V) 2.0 MAX5946 toc02 MAX5946 toc01 1.8 0 -40 OUTPUT VOLTAGE (V) 2.0 GATE CHARGE CURRENT (A) SUPPLY CURRENT (mA) 0.505 0.504 0.503 0.502 0.501 0.500 0.499 0.498 0.497 0.496 0.495 0.494 0.493 0.492 0.491 0.490 ON AND AUXON LOW-TO-HIGH THRESHOLD VOLTAGE vs. TEMPERATURE 3.3VAUXIN SUPPLY CURRENT vs. TEMPERATURE 12VIN INPUT SUPPLY CURRENT vs. TEMPERATURE 0.450 -40 -15 10 35 TEMPERATURE (C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (C) _______________________________________________________________________________________ 5 MAX5946 Typical Operating Characteristics Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, 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 10.10 UVLO THRESHOLD (V) UVLO THRESHOLD (V) MAX5946 Dual PCI Express, Hot-Plug Controller 10.05 10.00 9.95 2.66 2.64 9.90 2.62 9.85 9.80 2.60 -40 -15 10 35 60 85 -40 TEMPERATURE (C) -15 10 35 60 85 TEMPERATURE (C) 12V TURN-ON/OFF TIME 3.3V TURN-ON/OFF TIME MAX5946 toc12 MAX5946 toc13 3.3V OUTPUT 5V/div 12V OUTPUT 10V/div 3.3G_ 10V/div 12G_ 20V/div ON_ 5V/div ON_ 5V/div PWRGD_ 5V/div PWRGD_ 5V/div 40ms/div 40ms/div 3.3V AUXILIARY TURN-ON/OFF TIME 12V POWER-UP MAX5946 toc15 MAX5946 toc14 3.3AUXO_ OUTPUT VOLTAGE 2V/div 12G_ 20V/div 12V OUTPUT 10V/div PWRGD 2V/div 12VIN, 12V INPUT 10V/div AUXON_ 2V/div 40ms/div 6 PWRGD_ 5V/div 40ms/div _______________________________________________________________________________________ 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 3.3V OUTPUT (AUTORESTART OPTION MAX5946A) MAX5946 toc19 MAX5946 toc18 RLOAD STEP TO 1.5 tRESTART 12V OUTPUT CURRENT 5A/div RLOAD STEP TO 0.5 12G_ 20V/div 3.3G_ 10V/div 12V OUTPUT VOLTAGE 10V/div 3.3V OUTPUT VOLTAGE 5V/div FAULT_ 5V/div tRESTART FAULT_ 5V/div 100ms/div 100ms/div FAULT CONDITION ON AUXILIARY OUTPUT (AUTORESTART OPTION MAX5946A) FAULT CONDITION ON 12V OUTPUT (LATCH OPTION MAX5946L) MAX5946 toc20 RLOAD STEP TO 4 3.3V MAIN OUTPUT CURRENT 2A/div MAX5946 toc21 3.3VAUXO_ OUTPUT CURRENT 500mA/div RLOAD STEP TO 1.5 12V OUTPUT CURRENT 5A/div 12G_ 20V/div tRESTART 100ms/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div 12V OUTPUT VOLTAGE 10V/div FAULT_ 2V/div FAULT_ 5V/div 100ms/div _______________________________________________________________________________________ 7 MAX5946 Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, unless otherwise noted, see the Typical Application Circuit.) 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_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, 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 1.5 12V OUTPUT CURRENT 5A/div RLOAD STEP TO 0.5 12G_ 20V/div 3.3G_ 10V/div 12V OUTPUT VOLTAGE 10V/div 3.3V OUTPUT VOLTAGE 5V/div FAULT_ 5V/div FAULT_ 5V/div 100ms/div 4ms/div FAULT CONDITION ON AUXILIARY OUTPUT (LATCH OPTION MAX5946L) FAULT CONDITION ON 3.3V MAIN OUTPUT MAX5946 toc25 MAX5946 toc24 tFAULT 3.3V OUTPUT CURRENT 2A/div RLOAD STEP TO 0.5 3.3V OUTPUT CURRENT 2A/div RLOAD STEP TO 4 3.3VAUXO_ OUTPUT CURRENT 500mA/div 3.3G_ 10V/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div 3.3V OUTPUT VOLTAGE 5V/div FAULT_ 2V/div FAULT_ 5V/div 100ms/div 4ms/div SHORT CIRCUIT ON 12V OUTPUT FAULT CONDITION ON AUXILIARY OUTPUT MAX5946 toc27 MAX5946 toc26 tFAULT RLOAD STEP TO 4 12V OUTPUT CURRENT 5A/div 3.3VAUXO_ OUTPUT CURRENT 500mA/div 12G_ 20V/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div 12V OUTPUT VOLTAGE 10V/div FAULT_ 2V/div 4ms/div 8 FAULT_ 5V/div 2ms/div _______________________________________________________________________________________ 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 4s/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 3.3G_ 5V/div 3.3V OUTPUT VOLTAGE 5V/div FAULT_ 5V/div FAULT_ 5V/div 0V 2ms/div 2s/div POWER-UP INTO FAULT (AUXILIARY SUPPLY) SHORT CIRCUIT ON 3.3VAUXO_ MAX5946 toc32 MAX5946 toc33 RLOAD = 4 3.3VAUXO_ OUTPUT CURRENT 5A/div tSU 3.3VAUXO_ OUTPUT CURRENT 500mA/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div 3.3VAUXO_ OUTPUT VOLTAGE 2V/div AUXON_ 5V/div FAULT_ 5V/div 2s/div FAULT_ 5V/div 4ms/div _______________________________________________________________________________________ 9 MAX5946 Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, unless otherwise noted, see the Typical Application Circuit.) 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_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, 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 = 0.5 3.3V OUTPUT CURRENT 4A/div tSU 12V OUTPUT CURRENT 5A/div tSU 3.3G_ 5V/div 12G_ 10V/div 3.3V OUTPUT VOLTAGE 2V/div 12V OUTPUT VOLTAGE 10V/div ON_, AUXON_ 5V/div ON_, AUXON_ 5V/div FAULT_ 5V/div FAULT_ 5V/div 4ms/div 4ms/div PRESENT-DETECT (ON/OFF) OPERATION PRESENT-DETECT (ON/OFF) OPERATION MAX5946 toc36 MAX5946 toc37 12V OUTPUT VOLTAGE 10V/div 12V OUTPUT VOLTAGE 10V/div 5V/div 3.3VAUXO_ OUTPUT VOLTAGE 5V/div 3.3VAUXO_ OUTPUT VOLTAGE 5V/div PWRGD 5V/div PWRGD 5V/div PRES-DET_ 5V/div PRES-DET_ 40ms/div 4ms/div FORCED-ON (ON/OFF) OPERATION FORCED-ON (ON/OFF) OPERATION MAX5946 toc38 12V OUTPUT VOLTAGE 10V/div 12V OUTPUT VOLTAGE 10V/div 5V/div 3.3VAUXO_ OUTPUT VOLTAGE 5V/div 3.3VAUXO_ OUTPUT VOLTAGE 5V/div PWRGD 5V/div PWRGD 5V/div FON_ 5V/div FON_ 40ms/div 10 MAX5946 toc39 4ms/div ______________________________________________________________________________________ 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 (k) tFAULT TIME DELAY vs. TIM RESISTOR MAX5946 toc42 200 180 160 tFAULT (ms) 140 120 100 80 60 40 20 0 0 100 200 300 400 500 600 700 800 900 1000 RTIM (k) ______________________________________________________________________________________ 11 MAX5946 Typical Operating Characteristics (continued) (V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM = float, FAULT_ = 10k to 3.3VAUXIN, PWRGDA = 10k to 3.3VAUXO_, TA = +25C, unless otherwise noted, see the Typical Application Circuit.) 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. FONA has a 50k internal pullup to 3.3VAUXIN. A logic-low on FONA turns on all slot A outputs as long as the power inputs are within their operating range, regardless of the status of the other input signals. Leave FONA open for normal operation (see Table 2). 3 ONA Slot A 12V And 3.3V Outputs Enable. A logic-high at ONA turns on the 12V and 3.3V outputs of slot A (see Table 2). 4 AUXONA 5 12SA+ Slot A 12V Positive Current-Sense Input. Connect the positive terminal of the current-sense resistor to 12SA+ using the Kelvin-sensing technique to assure accurate current sensing. 6 12SA- Slot A 12V Negative Current-Sense Input. Connect 12SA- to the negative side of the current-sense resistor using the Kelvin-sensing technique to assure accurate current sensing. 7 12GA Slot A 12V Gate-Drive Output. Connect 12GA to the gate of slot A's 12V MOSFET. At power-up, V12GA is raised to the internal charge-pump voltage level by a constant current. 8 3.3SA+ Slot A 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to 3.3SA+ using the Kelvin-sensing technique to assure accurate current sensing. This input is also used for the 3.3V supply's UVLO function. 9 3.3SA- Slot A 3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using the Kelvin-sensing technique to assure accurate current sensing. 10 3.3GA Slot A 3.3V Gate-Drive Output. Connect 3.3GA to the gate of slot A's 3.3V MOSFET. At power-up, V3.3GA is charged to 5.5V above the 3.3V supply by a constant current derived from V12VIN. Slot A 3.3V Auxiliary Output Enable. A logic-high at AUXONA turns on the slot A auxiliary output (3.3VAUXOA), see Table 2. 11 FAULTA Open-Drain Fault Output Signal. FAULTA latches active low whenever the slot A outputs are shut down due to a fault. A fault is either of: * An overcurrent condition lasting longer than the overcurrent timeout. * A device over temperature condition. If the fault is detected in the main outputs, FAULTA must be reset by toggling the ONA input. If the fault is in the auxiliary output, FAULTA must be reset by toggling both ONA and AUXONA. For the autorestart version, FAULTA is reset when the part initiates the next power-on cycle. 12 PWRGDA Open-Drain Power-Good Output. PWRGDA goes low tPOR_HL after all outputs of slot A reach their final value and the power MOSFETs are fully enhanced. 13 3.3VAUXOA Slot A 3.3V Auxiliary Power-Supply Output 14 3.3VAUXIN 3.3V Auxiliary Supply Input. 3.3VAUXIN is the input to a charge pump that drives the internal MOSFETs connecting 3.3VAUXIN to 3.3VAUXOA and 3.3VAUXOB. V3.3VAUXIN is also used to power the internal control logic and analog references of the MAX5946. 15 3.3VAUXOB Slot B 3.3V Auxiliary Power Output 16 PWRGDB 17 FAULTB 18 3.3GB Slot B Power-Good Output. See PWRGDA function. Slot B Open-Drain Fault Output. See FAULTA function. Slot B 3.3V Gate-Drive Output. See 3.3GA function. ______________________________________________________________________________________ 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. See 12SA+ function. 24 AUXONB 25 ONB 26 FONB 27 PRES-DETB 28 TIM Slot B 3.3V Auxiliary Output Enable. See AUXONA function. Slot B 12V And 3.3V Outputs Enable. See ONA function. Slot B Forced-On Input. See FONA function. Slot B Present-Detect Input. See PRES-DETA function. Overcurrent Timeout Programming Input. Connect a resistor between 500 and 500k from TIM to GND to program tFAULT. Leave TIM floating for a default timeout of 11ms. 29 INPUT2 30 OUTPUT2 Digital Logic Gate Input 31 OUTPUT1 32 INPUT1 33 12VIN 12V Supply Input. V12VIN drives the gates of the MOSFETs connected to 3.3GA and 3.3GB. 12VIN powers an internal charge pump that drives the gates of the MOSFETs connected to 12GA and 12GB. 34 GND Ground 35 PGND 36 PORADJ Digital Output. 4ms debounced digital output of INPUT2. Digital Output. 4ms debounced digital output of INPUT1. Digital Logic Gate Input Power Ground. Connect externally to GND. Power-On-Reset Programming Input. Connect a resistor between 500 and 500k from PORADJ to GND to program the POR timing. Leave floating for a default value of 160ms. Detailed 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/outputs allow interfacing directly with the system hot-plug-management controller or through an SMBus with an external I/O expander. An integrated debounced attention 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 auxiliary outputs are controlled through internal 0.24 nchannel MOSFETs. Internal charge pumps provide a 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 all supplies rise above their respective UVLO thresholds. The device keeps the internal MOSFETs off only until the 3.3VAUXIN 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. Thermalprotection circuitry also shuts down all outputs if the die temperature exceeds +150C. After an overcurrent or overtemperature fault condition, the MAX5946L latches off while the MAX5946A automatically restarts after a restart time delay. The power requirement for PCI express connectors is defined by the PCI express card specification and summarized in Table 1. ______________________________________________________________________________________ 13 MAX5946 Pin Description (continued) 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 12SB5A 5A 12GA 10A 150A 12GB A01 10A tFAULT OSCILLATOR DEBOUNCE tPOR OSCILLATOR FAST OSCILLATOR A 0 0 1 100mA 100mA 150A MAX5946 3.3SA+ 3.3SB+ 100mV RSENSE3.3A 20mV + - + - + - 100mV + - RSENSE3.3B 20mV 3.3SA- 3.3SB5A 50A 3.3GA 3.3GB BIAS REFERENCES AND UVLO 10A A 0 1 10A CONTROL LOGIC MAIN-SLOT B CONTROL LOGIC MAIN-SLOT A 150A A051 150mA 150mA 150A 3.3VAUXIN VREF + - VREF + CHARGE PUMP CHARGE PUMP CONTROL LOGIC AUX-SLOT B CONTROL LOGIC AUX-SLOT A 3.3VAUXOA 3.3VAUXOB INPUT COMPARATORS AND CHIP-CONTROL LOGIC PGND GND ONA AUXONA FONA PRES-DETA ONB AUXONB FONB PRES-DETB Figure 1. Functional Diagram 14 ______________________________________________________________________________________ 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) 1000F (max) 1000F (max) 1000F (max) Voltage Tolerance 8% (max) 8% (max) 8% (max) Supply Current 0.5A (max) 2.1A (max) 5.5A (max) 300F (max) 1000F (max) 2000F (max) 9% (max) 9% (max) 9% (max) Supply Current, Wake Enabled 375mA (max) 375mA (max) 375mA (max) Supply Current, Non-Wake Enabled 20mA (max) 20mA (max) 20mA (max) Capacitive Load 150F (max) 150F (max) 150F (max) 3.3V Capacitive Load 12V Capacitive Load 3.3V AUXILIARY Voltage Tolerance Table 2. Control Logic Truth Table ON_ AUXON_ FON_ PRES-DET_ 12V_ AND 3.3V_ OUTPUTS 3.3VAUXO_ AUXILIARY OUTPUTS X X Low X On On X X High High Off Off Low Low High Low* Off Off High Low High Low* On Off Low High High Low* Off On High High High Low* On On *PRES-DET_ high-to-low transition has a 4ms delay (tDEG). Startup The main supply outputs can become active only after all the following events have occurred: * V3.3VAUXIN is above its UVLO threshold * V 12VIN and V 3.3SA+ are both above their UVLO threshold * ON_ is driven high * PRES-DET_ is low for more than 4ms The auxiliary supply output is made available only after the following events have occurred: * V3.3VAUXIN is above its UVLO threshold * AUXON_ is driven high * PRES-DET_ is low for more than 4ms The FON_ input overrides all other control signals and turns on the respective slot when driven low, as long as the UVLO thresholds have been reached. Table 2 summarizes the logic conditions required for startup. The auxiliary supply input powers the internal control logic and analog references of the MAX5946, so the main supplies cannot be enabled if V3.3VAUXIN is not present. When an output is enabled, a programmable startup timer (tSU) begins to count the startup time duration. The value of tSU is set to 2x the fault timeout period (tFAULT). RTIM externally connected from TIM to GND sets the duration of tFAULT. ______________________________________________________________________________________ 15 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. Figure 2. Power-Up Timing, No Fault Figure 3. 12V Power-Up Timing (Turn-On into Output Overcurrent/Short Circuit) controller disengages both the 12V and 3.3V outputs for the particular slot (see the Fault Management section). 3.3V Auxiliary Output Normal Operation 12G_ V12ILIM,TH RSENSE 12V OUTPUT CURRENT PWRGD_ The auxiliary output current is internally monitored and actively limited to the maximum current-limit value. An overcurrent fault condition occurs when the output current exceeds the overcurrent threshold for longer then tFAULT. A fault on an auxiliary channel causes all supplies of the affected channel to be disabled after a programmable time period t FAULT (see the Fault Management section). Power-Good (PWRGD_) 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. Figure 4. 12 Output Overcurrent/Short Circuit During Normal Operation 12V and 3.3V Outputs Normal Operation The MAX5946 monitors and actively limits the current of the 12V and 3.3V outputs after the startup period. Each output has its own overcurrent threshold. If any of the monitored output currents rise above the overcurrent threshold for a period tFAULT, FAULT_ asserts and the 16 Power-good (PWRGD_) is an open-drain output that pulls low a time (tPOR_HL) after all of the outputs of the respective slot are fully on. All outputs are considered fully on when 3.3G_ has risen to VPGTH3.3, 12G_ has risen to V PGTH12 , and V 3.3AUXO_ is less then V PGTH3.3AUX . t POR_HL is adjustable from 2.5ms to 1.5s by connecting a resistor from PORADJ to GND. See the Setting the Power-On-Reset Timeout Period (tPOR) section. Thermal Shutdown When the die temperature goes above (TSD) +150C, an overtemperature fault occurs and the MAX5946 shuts down all outputs. The device waits for the junction temperature to decrease below TSD - Hysteresis before entering fault management (see the Fault Management section). ______________________________________________________________________________________ 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. If an overcurrent fault occurred on a main output, bring ON_ low for at least tRESET (100s) and high again to reset the fault and restart the outputs. If the overcurrent fault occurred on an auxiliary output or an overtemperature fault occurred, bring both ON_ and AUXON_ low for a minimum of tRESET to reset the fault. Bring ON_ and/or AUXON_ high again to restart the respective outputs. As an extra protection, the MAX5946L waits a minimum of tRESTART before it can be restarted. Debounced Logic Gate (Input_ and Output_) INPUT1 and INPUT2 accept inputs from mechanical switches. The corresponding outputs are OUTPUT1 and OUTPUT2. OUTPUT_ is debounced for 4ms. When INPUT_ goes from high to low, OUTPUT_ goes low right away and stays low for at least 4ms. After the debounce time OUTPUT_ follows INPUT_. If INPUT_ goes from low to high, OUTPUT_ goes high right away and stays high for at least 4ms. After the debounce time, OUTPUT_ follows INPUT_. Figure 5 shows the timing diagram describing the INPUT_/OUTPUT_ debounced feature. Present-Detect and Forced-On Inputs (PRES-DET_, FON_) PRES-DETA and PRES-DETB inputs detect the PRSNT#2 pin on a PCI express connector. When the card is plugged in, PRES-DET_ goes low and allows the turn-on of the outputs of the respective slot after a INPUT tDBC tDBC tDBC DEBOUNCED OUTPUT 4ms debounced time. When the card is removed, an internal 50k pullup forces PRES-DET_ high and the respective slot is shut down with no delay. PRES-DET_ works in conjunction with ON_ and VAUXON_ and only enables the device when ON_ and VAUXON_ are high. A logic-low on FON_ forces the respective slot (main supplies and auxiliary) to turn on regardless of the status of the other logic inputs provided the UVLO thresholds are exceeded on all of the inputs. Active Current Limits Active current limits are provided for all three outputs of slot A and slot B. Connect a current-sense resistor between 12S_+ and 12S_- to set the current limit for the 12V outputs. The current limit is set to 54mV/RSENSE12. RSENSE12 is either R1 or R3 in the Typical Application Circuit. Connect a current-sense resistor between 3.3S_+ and 3.3S_- to set the current limit for the 3.3V main outputs to 20mV/RSENSE3.3. RSENSE3.3 is either R2 or R4 in the Typical Application Circuit. For the auxiliary output (3.3VAUXO_) the current limit is fixed at 470mA. When the voltage across R SENSE12 or R SENSE3.3 reaches the current-limit threshold voltage, the MAX5946 regulates the gate voltage to maintain the current-limit threshold voltage across the sense resistor. If the current limit lasts for tFAULT then an overcurrent fault occurs. The MAX5946_ shuts down both the 12V and 3.3V outputs and asserts the FAULT_ output of the respective slot. When the auxiliary output reaches the current limit (470mA) for longer then tFAULT, a fault occurs and the device shuts down all outputs and asserts FAULT of the respective slot. Undervoltage Lockout Threshold The UVLO thresholds prevent the internal auxiliary MOSFETs and the external main channel MOSFETs (Q1-Q4 in the Typical Application Circuit) from turning on if V12VIN, V3.3VIN, and V3.3VAUXIN are not present. Internal comparators monitor the main supplies and the auxiliary supply and keep the gate-drive outputs (12GA, 12GB, 3.3GA, and 3.3GB) low until the supplies rise above their UVLO threshold. The 12V main supply is monitored at 12VIN and has a UVLO threshold of 10V. The 3.3V main supply is monitored at 3.3SA+ and has a UVLO threshold of 2.65V. The auxiliary supply is monitored at 3.3VAUXIN and has a 2.65V UVLO threshold. For either main channel to operate, V3.3VAUXIN must be above its UVLO threshold. Figure 5. INPUT_ and OUTPUT_ Debounced Feature ______________________________________________________________________________________ 17 MAX5946 FAULT Management A fault occurs when an overcurrent lasts longer then tFAULT or when the device experiences an overtemperature condition. 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. START COUNTING tSU POWER-ON MAIN SUPPLIES FAULT AND PWRGD ARE HIGH IMPEDANCE 3.3AUXIN IS ON AND ABOVE UVLO Y HAS tSU ELAPSED? ARE PWRGD THRESHOLDS REACHED? RESET PWRGD_ AFTER tPOR_LH DELAY N Y STAY WAITING FOR BOTH ON_ AND AUXON_ TRANSITION HIGH->LOW->HIGH RESET FAULT_ AND RESTART ALL SUPPLIES ASSERT PWRGD_ AFTER tPOR_HL DELAY N Y LATCH-OFF OPTION? POWER-ON AUXILIARY SUPPLIES FAULT AND PWRGD ARE HIGH IMPEDANCE N SHUT DOWN ALL OUTPUTS, ASSERT FAULT_, STAY WAITING FOR tRESTART ELAPSED. Y ENABLE CHARGE ON INTERNAL AUXILIARY MOSFET, BEGIN COUNTING tSU IS tFAULT ELAPSED? START COUNTING tFAULT HAS tSU ELAPSED? Y AUX SUPPLY OUTPUT IS ENABLED N N IS FAULT STILL PRESENT? WAS CURRENT LIMIT DETECTED ON AUXILIARY OUTPUT? Y Y N RESET tFAULT COUNTER Figure 6. Fault Management Flow Chart 18 ______________________________________________________________________________________ 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 5A into the external gate capacitance to control the turn-on time of the external MOSFET. During turn-off, 12G_ sinks 150A from the external gate capacitance to quickly turn off the external MOSFET. During short-circuit events, an internal 100mA current activates to rapidly bring the load current into the regulation limits. 3.3G_ is the gate drive for the 3.3V main supply's MOSFET and is driven to 5.5V above the 3.3V main supply. The power for 3.3G_ is supplied from 12VIN and has no internal charge pump. During turn-on, 3.3G_ sources 5A into the external gate capacitance to control the turn-on time of the external MOSFET. During turn-off, 3.3G_ sinks 150A to quickly turn off the external MOSFET. During short-circuit events, an internal 150mA current activates to rapidly turn off the appropriate external MOSFET. Auxiliary Supply (3.3VAUXIN) 3.3VAUXIN provides power to the auxiliary outputs as well as the internal logic and references. The drains of the internal auxiliary MOSFETs connect to 3.3VAUXIN through internal sense resistors and the sources connect to the auxiliary outputs (3.3VAUXOA and 3.3VAUXOB). Both MOSFETs have typical on-resistance of 0.3. An internal charge pump boosts the gate-drive voltage to fully turn on the internal n-channel MOSFETs. The auxiliary supplies have an internal current limit set to 470mA. Applications Information Setting the Fault Timeout Period (tFAULT) tFAULT is the time an overcurrent or overtemperature fault must remain for the MAX5946 to disable the main or auxiliary channels of a particular slot. Program the fault timeout period (tFAULT) by connecting a resistor (RTIM) from TIM to GND. tFAULT can be calculated by the following equation: tFAULT = 166ns / x RTIM The tFAULT programmed time duration must be chosen according to the total capacitance load connected to the 12G_ and 3.3G_ pins. To properly power-up the main supply outputs, the following constraints need to be taken: V x CLOAD t SU GATE ICHG where tSU = 2 x tFAULT and where 1) ICHG = 5A. 2) V GATE = 18.4V for 12G_ and V GATE = 9.4V for 3.3G_. 3) CLOAD is the total capacitance load at the gate. Maximum and minimum values for RTIM are 500 and 500k, respectively. Leave TIM floating for a default tFAULT of 11ms. Setting the Power-On-Reset Timeout Period (tPOR_HL) tPOR_HL is the time from when the gate voltages of all outputs of a slot reach their power-good threshold to when PWRGD_ pulls low. Program the power-on-reset timeout period (tPOR) by connecting a resistor (RPORADJ) from PORADJ to GND. tPOR_HL can be calculated by the following equation: tPOR_HL = 2.5s / x RPORADJ Maximum and minimum values for RPORADJ are 500 and 500k, respectively. Leave PORADJ floating for a default tPOR of 160ms. Component Selection Select the external n-channel MOSFET according to the applications current requirement. Limit the switch power dissipation by choosing a MOSFET with an RDS_ON low enough to have a minimum voltage drop at full load. High RDS_ON causes larger output ripple if there are pulsed loads. High RDS_ON can also trigger an external undervoltage fault at full load. Determine the MOSFETs power rating requirement to accommodate a short-circuit condition on the board during startup. Table 3 lists MOSFETs and sense resistor manufacturers. Additional External Gate External capacitance can be added from the gate of the external MOSFETs to GND to slow down the dV/dt of the 12V and 3.3V outputs. Maximum Load Capacitance Large capacitive loads at the 12V output, the 3.3V output, and the 3.3V auxiliary output can cause a problem when inserting discharged PCI cards into live backplanes. A fault occurs if the time needed to charge the capacitance of the board is greater than the typical startup time (2 x tFAULT). The MAX5946 can withstand ______________________________________________________________________________________ 19 MAX5946 External MOSFET Gate Drivers (12GA, 12GB, 3.3GA, and 3.3GB) 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. Calculate the maximum load capacitance as follows: t xI CLOAD < SU LIM VOUT VOUT is either the 3.3V output, the 12V output, or the 3.3V auxiliary output for slot A or slot B. www.vishay.com thresholds before startup can occur. Input transients can cause the input voltage to sag below the UVLO threshold. The MAX5496 rejects transients on the input supplies that are shorter than 4s typical. Chip Information TRANSISTOR COUNT: 10,487 PROCESS: BiCMOS Input Transients The 12V input (12VIN), the 3.3V input (3.3SA+), and the 3.3V auxiliary (3.3VAUXIN) must be above their UVLO 20 ______________________________________________________________________________________ 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 8m Q3 SI7448DP-T1 R3 8m PRSNT1 +12V +12V PWRGD 12GB 12SB+ 12VIN 3.3VAUXIN 12SA+ 12SA- 12GA GND 112SB- 1F 0.1F GND PWRGD PWRGDB PWRGDA 10k 10k MAX5946 3.3VAUX 3.3VAUXOA 3.3VAUX 3.3VAUXOB RPORADJ = OPEN 3.3SB- 3.3SB+ TIM PRES-DETB OUTPUT1 / OUTPUT2 INPUT1 / INPUT2 ONA / ONB AUXONA / AUXONB FONA / FONB FAULTA / FAULTB PRES-DETA 3.3SA+ 3.3SA- 3.3GA 3.3GB PORADJ GND RTM = OPEN Q2 SI7448DP-T1 2 R2 5m 2 R4 5m V3.3AUXIN 2 2 0.1F PRSNT2 10k MAX7313ATG 16-BIT I/O EXPANDER MRL LED's 2 3.3V INPUT ATTENTION SWITCHES 2 PRSNT2 Q4 SI7448DP-T1 +3.3V +3.3V MRL 2 2 2 LED's 3 SMBus AO-2 INT ______________________________________________________________________________________ 21 MAX5946 Typical Application Circuit 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.EPS MAX5946 Dual PCI Express, Hot-Plug Controller 22 ______________________________________________________________________________________ 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 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX5946 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.)