MIC2341 Datasheet, PDF (5/32 Pages) Micrel Semiconductor – Dual-Slot PCI Express Hot-Plug Controller

Micrel, Inc.
MIC2341/2341R
Pin Description
Pin Number
5
32
12
25
16
21
10
27
8
29
13
24
3
24
Pin Name
12VINA
12VINB
3VINA
3VINB
3VOUTA
3VOUTB
12VOUTA
12VOUTB
12VSENSEA
12VSENSEB
3VSENSEA
3VSENSEB
12VGATEA
12VGATEB
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 MIC2341
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 MIC2341
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 tFLT or tDFLT (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 tFLT or tDFLT (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 CGATE (if used) and the
CGS 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 tFLT or tDFLT (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.
October 2007
5
M9999-102507-A
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