
MIC2592B
Micrel
March 2005
4
M9999-033105
Pin Description
Pin Number
Pin Name
Pin Function
turning on while this input is less than its lockout threshold.
turning on while this input is less than its lockout threshold.
21
3VOUTB
monitor the 3.3V output voltages for Power-is-Good status.
27
12VOUTB
monitor the 12V output voltages for Power-is-Good status.
, the circuit breaker is tripped and the GATE pin for the affected 12V
FLT
supply’s external MOSFET is immediately pulled high.
, the circuit breaker is tripped and the GATE pin for the affected 3V
FLT
supply’s external MOSFET is immediately pulled low.
GATE
and the C
GS
of the
. Whenever an
supply for the affected slot is shut-down.
FLT
GATE
and the C
GS
of the
. Whenever an
supply for the affected slot is shut down.
FLT
pins. An undervoltage lockout circuit (UVLO) prevents the switches from
pins. An undervoltage lockout circuit (UVLO) prevents the switches from
16
3VOUTA
3.3V Power-Good Sense Inputs: Connect to 3.3V[A/B] outputs. Used to
10
12VOUTA
12V Power-Good Sense Inputs: Connect to 12V[A/B] outputs. Used to
for t
for t
are charged by an internal current source during power-down. Also, the 3V
down, these pins are discharged by an internal current source. Also, the 12V
the MIC2592B controller in order to eliminate any IR drop between these
the MIC2592B controller in order to eliminate any IR drop between these
therefore a constant current into the load. If the 50mV threshold is exceeded
therefore a constant current into the load. If the 50mV threshold is exceeded
the GATE pin for the affected slot is immediately brought high. These pins
the GATE pin for the affected slot is immediately brought low. During power-
5
32
12VINA
12VINB
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
12
25
3VINA
3VINB
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
8
29
12VSENSEA
12VSENSEB
12V Circuit Breaker Sense Inputs: The current limit thresholds are set
by connecting sense resistors between these pins and 12VIN[A/B]. When
the current limit threshold of IR = 50mV is reached, the 12VGATE[A/B] pin
is modulated to maintain a constant voltage across the sense resistor and
13
24
3VSENSEA
3VSENSEB
3V Circuit Breaker Sense Inputs: The current limit thresholds are set by
connecting sense resistors between these pins and 3VIN[A/B]. When the
current limit threshold of IR = 50mV is reached, the 3VGATE[A/B] pin is
modulated to maintain a constant voltage across the sense resistor and
3
34
12VGATEA
12VGATEB
12V Gate Drive Outputs: Each pin connects to the gate of an external
P-Channel MOSFET. During power-up, the C
MOSFETs are connected to a 25μA current sink. This controls the value of
dv/dt seen at the source of the MOSFETs.
During current limit events, the voltage at this pin is adjusted to maintain
constant current through the switch for a period of t
overcurrent, thermal shutdown, or input undervoltage fault condition occurs,
14
23
3VGATEA
3VGATEB
3V Gate Drive Outputs: Each pin connects to the gate of an external
N-Channel MOSFET. During power-up, the C
MOSFETs are connected to a 25μA current source. This controls the value
of dv/dt seen at the source of the MOSFETs, and hence the current flowing
into the load capacitance.
During current limit events, the voltage at this pin is adjusted to maintain
constant current through the switch for a period of t
overcurrent, thermal shutdown, or input undervoltage fault condition occurs,