MIC2342/2342R
Dual-Slot PCI Express
®
Hot-Plug
Controller
General Description
The MIC2342 is a dual-slot power controller supporting the
power distribution requirements for Peripheral Component
Interconnect Express (PCI Express
®
) Hot-Plug compliant
systems. The MIC2342 provides complete power control
support for two PCI Express slots, including the 3.3VAUX
defined by the PCI Express standards. Support for the
12V, 3.3V, and 3.3VAUX supplies includes programmable
gate voltage slew-rate control, voltage supervision,
programmable current limit, and circuit breaker functions.
These features provide comprehensive system protection
and fault isolation. Additionally, in the event of an
overcurrent fault on 3.3VAUX that “trips” the circuit breaker
to cause the 3.3VAUX output to shut down, the MAIN
outputs (3.3V and 12V) for the affected 3.3VAUX slot, A or
B, will also be shut down. The MIC2341 controller
provides truly independent output operation for MAIN and
AUX.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
•
Supports two independent PCI Express slots
•
MAIN & AUX outputs are inter-dependent during AUX
overcurrent conditions
•
12V, 3.3V, and 3.3VAUX supplies supported per PCI
Express Specification v1.0a, v.2.0
•
Integrated Power MOSFETS for 3.3VAUX rails
•
Standby Operation for Wake-on-LAN applications with
low backfeed on Main +12V and +3.3V rails
•
Electronic circuit breakers for each supply per slot
-
Programmable gate voltage slew-rate control
-
Active current regulation controls inrush current
•
High accuracy Primary and Secondary Circuit Breaker
Current-limit Thresholds
•
Dual-level, dual-speed fault detection for fast response
without nuisance tripping
•
User-programmable Primary Overcurrent Detector
•
/PWRGD and Delayed /PWRGD (164 ms) Signal
Outputs per slot
•
Separate /FAULT output signals for MAIN and AUX
rails for each slot
•
Global Systems Power-is-Good Output
•
Both slots thermally isolated
•
Internally Debounced Plug-in Card Retention Switch
Inputs per slot.
Applications
•
PCI Express v1.0a, v2.0 hot-plug power control
June 2008
1
M9999-062008-A
Micrel, Inc.
MIC2342/2342R
Pin Description
Pin Number
5
32
Pin Name
12VINA
12VINB
Pin Function
12V Supply Power and Sense Inputs [A/B]: Two pins are provided for Kelvin
connection (one for each slot). Pin 5 is the (+) Kelvin-sense connection to the
supply side of the sense resistor for 12V Slot A. Pin 32 is the (+) Kelvin-sense
connection to the supply side of the sense resistor for 12V Slot B. These two
pins must ultimately connect to each other as close as possible at the MIC2342
controller in order to eliminate any IR drop between these pins. An undervoltage
lockout circuit (UVLO) prevents the switches from turning on while this input is
lower than its lockout threshold voltage.
3.3V Supply Power and Sense Inputs [A/B]: Two pins are provided for
connection (one for each slot). Pin 12 is the (+) Kelvin-sense connection to the
supply side of the sense resistor for 3V Slot A. Pin 25 is the (+) Kelvin-sense
connection to the supply side of the sense resistor for 3V Slot B. These two pins
must ultimately connect to each other as close as possible at the MIC2342
controller in order to eliminate any IR drop between these pins. An undervoltage
lockout circuit (UVLO) prevents the switches from turning on while this input is
lower than its lockout threshold voltage.
3.3V Power-Good Sense Inputs: Connect to 3.3V[A/B] outputs. Used to monitor
the 3.3V output voltages for 3.3V Output Power-is-Good status.
12V Power-Good Sense Inputs: Connect to 12V[A/B] outputs. Used to monitor
the 12V output voltages for 12V Output Power-is-Good status.
12V Circuit Breaker Sense Input [A/B]: The current limit thresholds are set by
connecting sense resistors between these pins and 12VIN[A/B]. When the 12V
primary overcurrent detector current-limit threshold of 50mV is reached, the
12VGATE[A/B] pin is modulated to maintain a constant voltage across the sense
resistor and therefore a constant current into the load. If the 50mV threshold is
exceeded for t
FLT
or t
DFLT
(whichever is shorter), the circuit breaker is tripped and
the corresponding 12VGATE pin for the affected slot is immediately pulled up to
its corresponding 12VIN to turn OFF the external MOSFET.
3V Circuit Breaker Sense Input [A/B]: The current limit thresholds are set by
connecting sense resistors between these pins and 3VIN[A/B]. When the 3V
primary overcurrent detector current-limit threshold of 50mV is reached, the
3VGATE[A/B] pin is modulated to maintain a constant voltage across the sense
resistor and therefore a constant current into the load. If the 50mV threshold is
exceeded for t
FLT
or t
DFLT
(whichever is shorter), the circuit breaker is tripped and
the corresponding 3VGATE pin for the affected slot is immediately pulled down
to AGND to turn OFF the external MOSFET.
12V Gate Drive Outputs [A/B]: Each pin connects to the gate of an external P-
channel power MOSFET. During power-up, the external C
GATE
(if used) and the
C
GS
of the external MOSFETs are connected to a 25µA current sink. This
controls the value of dv/dt seen at the source of the MOSFETs, and hence the
current flowing into the 12V load capacitance.
During current limit events, the voltage at this pin is adjusted to maintain
constant current through the FET for a period of t
FLT
or t
DFLT
(whichever is
shorter). Whenever an overcurrent, thermal shutdown, or input undervoltage
fault condition occurs, the corresponding 12VGATE pin for the affected slot is
pulled up to its corresponding 12VIN pin to turn OFF the external MOSFET.
12
25
3VINA
3VINB
16
21
10
27
8
29
3VOUTA
3VOUTB
12VOUTA
12VOUTB
12VSENSEA
12VSENSEB
13
24
3VSENSEA
3VSENSEB
3
24
12VGATEA
12VGATEB
June 2008
5
M9999-062008-B
Microcontroller MCU
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