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
ExpanderApplicationServers
Desktop Mobile Server Platforms
Workstations
Embedded DevicesPinout
Specifications(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 (V 3.3VAUXIN+ 0.3V)
Continuous Power Dissipation (TA= +70°C)
36-Pin Thin QFN (derate 26.3mW/°C above +70°C).........2.105W
Operating Temperature Range.............................-40°C to +85°C
Junction Temperature........................................................+150°C
Storage Temperature Range...............................-65°C to +150°C
Lead Temperature (soldering, 10s)....................................+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functionaloperation 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.
DescriptionThe 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 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 0.3Ωn-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 +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 available in a 36-pin (6mm *6mm) thin QFN package andoperates over the -40°C to +85°C temperature range.
MAX5946 Data Sheet
