MIC2580A
Pin Number
7
8
Pin Name
/LPCIRST
/EPWRGD
Pin Function
Micrel, Inc.
Local PCI Reset (Open-Drain Output): Local PCI reset output to PCI
controller. Compliant to CompactPCI specification for LOCAL_PCI_RESET.
Early Power Good (Open-Drain Output): This signal goes active should
/FAULT or /PWRGD go active. No deglitch filtering is provided. This signal
satisfies PCI /RST timing for T
FAIL
per PCI Local Bus Specification, ver-
sion 2.1.
Power Good (Open-Drain Output): Active-low output goes active when all
supplies are within tolerance. (A 20µs delay is inserted prior to activation to
reduce nuisance tripping.)
Precharge Supply (Output): (MIC2580A-1.0) +1V
±20%
supply used for
precharge bias for I/O terminations (CompactPCI only).
Ground
–12V Supply (Input): Input for internal –12V switch.
–12V Switched Supply (Output): Switched –12V supply to PCI Hot Plug
compliant socket. Load carrying output.
On-Off Control (Input): Logic low turns on all switches; logic high turns off all
switches. Also used to reset the device from a circuit breaker condition. The
/ON pin is edge-triggered and requires a high-to-low transition once all four
supplies are above their respective thresholds.
Reset Delay (External Component): Connect to external capactior (C
RST
) to
increase power-on reset delay.
Reset (Open-Drain Output): Active-low signal remains active for a time
determined by C
RST
after all supplies are within tolerance; i.e., /PWRGD is
active. This signal may be used as a reset for logic controllers.
Slew (External Component): Connect to external capacitor (C
SLEW
) to
program the output slew rate of 3VGATE, 5VGATE, 12VGATE (internal) and
M12VGATE (internal).
Start-Up Timer (External Component): Connect to external capacitor
(C
START
) to increase the filter delay used to gate the /FAULT output upon
start-up. Used to prevent nuisance tripping during turn-on of supplies.
Fault (Open-Drain Output/Input): This active-low output signal activated
upon overcurrent or thermal shutdown. Includes 20µs deglitch filter. Fault is
reset using /ON.
Forcing pin low turns off all switches but does not activate the circuit breaker
function.
5V Supply (Input): +5V-supply input for current monitoring (reference
voltage for 5VSENSE). Not a load-current carrying input.
+5V Current Sense (Input): Measures voltage drop across an external
sense resistor with respect to 5VIN for overcurrent detection through the +5V
switch.
+5V Output Voltage Sense (Input): Connect to source of external N-channel
MOSFET (+5V switched output) to monitor for output undervoltage condi-
tions.
5V Gate Drive (Output): Drives gate of external N-channel MOSFET +5V
switch. Adding capacitance will slow the slew rate of the external MOSFET
switch turn-on. (The external MOSFET’s gate is charged by an internal
current source.)
12V Supply (Input): MIC2580A power supply and input for internal +12
switch. Supplies power for internal circuitry.
9
/PWRGD
10
11
12
13
14
VPCHG
GND
M12VIN
M12VOUT
/ON
15
16
CRST
/POR
17
CSLEW
18
CSTART
19
/FAULT
20
21
5VIN
5VSENSE
22
5VOUT
23
5VGATE
24
12VIN
February 2005
3
MIC2580A
MICREL [ MICREL SEMICONDUCTOR ]
