MAX5946 Datasheet, PDF (1/23 Pages) Maxim Integrated Products – Dual PCI Express, Hot-Plug Controller

19-3483; Rev 0; 11/04
EVAALVUAAILTAIOBNLEKIT
Dual PCI Express, Hot-Plug
Controller
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
Typical Application Circuit appears at end of data sheet.
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
Ordering Information
PART
MAX5946AETX
MAX5946LETX
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
36 Thin QFN
36 Thin QFN
Pin Configuration
TOP VIEW
36 35 34 33 32 31 30 29 28
PRES-DETA 1
FONA 2
ONA 3
AUXONA 4
12SA+ 5
12SA- 6
12GA 7
3.3SA+ 8
3.3SA- 9
MAX5946
27 PRES-DETB
26 FONB
25 ONB
24 AUXONB
23 12SB+
22 12SB-
21 12GB
20 3.3SB+
19 3.3SB-
10 11 12 13 14 15 16 17 18
SMBus is a trademark of Intel Corp.
PCI Express is a trademark of PCI-SIG Corp.
THIN QFN
________________________________________________________________ Maxim Integrated Products 1
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