Micrel, Inc.
Pin Number
6, 31
Pin Name
5VINA, 5VINB
Pin Function
MIC2593
5V Supply Power and Sense Input [A/B]: Pin 6 is the (+) Kelvin-sense
connection to the supply side of the sense resistor for 5V Slot A. Pin 31 is the
(+) Kelvin sense connection to the supply side of the sense resistor for 5V Slot
B. These two pins must ultimately connect to each other within10cm of the
MIC2593. An undervoltage lockout circuit (UVLO) prevents the switches from
turning on while this input is less than its lockout threshold.
5V Circuit Breaker Sense Input [A/B]: The current limit thresholds are set by
connecting sense resistors between these pins and 5VIN[A/B]. When the
current limit threshold of IR = 50mV is reached, the 5VGATE[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
(see CFILTER[A/B] pin description), the circuit breaker is tripped and the
GATE pin for the affected supply’s external MOSFET is immediately pulled low.
5V Power-Good Sense Inputs: Connect to 5V[A/B] outputs. Used to monitor the
5V output voltages for Power-is-Good status.
5V Gate Drive Output [A/B]: Each pin connects to the gate of an external N-
Channel MOSFET. During power-up, the C
GATE
and the C
GS
of the MOSFETs
are charged by 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 the pin is adjusted to maintain constant
current through the switch for a period of t
FLT
. Whenever an overcurrent, thermal
shutdown, or input undervoltage fault condition occurs, the GATE pin for the
affected slot is immediately brought low.
During power-down, these pins are discharged by an internal current source.
7, 30
5VSENSEA, 5VSENSEB
9, 28
8, 29
5VOUTA, 5VOUTB
5VGATEA, 5VGATEB
12, 25
3VINA, 3VINB
3.3V Supply Power and Sense Input [A/B]: Pin 12 is the (+) Kelvin-sense
connection to the supply side of the sense resistor for 3.3V Slot A. Pin 25 is the
(+) Kelvin-sense connection to the supply side of the sense resistor for 3.3V Slot
B. These two pins must ultimately connect to each other within 10cm of the
MIC2593. An undervoltage lockout circuit (UVLO) prevents the switches from
turning on while this input is less than its lockout threshold.
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
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
therefore a constant current into the load. If the 50mV threshold is exceeded for
t
FLT
(see CFILTER[A/B] pin description), the circuit breaker is tripped and the
GATE pin for the affected supply’s external MOSFET is immediately pulled low.
3.3V Power-Good Sense Inputs: Connect to 3.3V[A/B] outputs. Used to monitor
the 3.3V output voltages for Power-is-Good status.
3V Gate Drive Output [A/B]: Each pin connects to the gate of an external N-
channel MOSFET. During power-up, the C
GATE
and the C
GS
of the 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
FLT
. Whenever an
overcurrent, thermal shutdown, or input undervoltage fault condition occurs, the
GATE pin for the affected slot is immediately brought low. During power down,
these pins are discharged by an internal current source.
13, 24
3VSENSEA, 3VSENSEB
16, 21
14, 23
3VOUTA, 3VOUTB
3VGATEA, 3VGATEB
11, 26
VSTBYA, VSTBYB
.3V Standby Input Voltage: Required to support PCI VAUX output. Additionally,
the SMBus logic and internal registers run off of VSTBY[A/B] to ensure that the
MIC2593 is accessible during standby modes. A UVLO circuit prevents turn-on
of this supply until VSTBY[A/B] rises above its UVLO threshold. Both pins must
be connected together externally at the IC.
September 2008
4
M9999-092208
MICREL [ MICREL SEMICONDUCTOR ]
