MIC2580A-1.6YTS-TR [MICROCHIP]
Power Supply Support Circuit, Adjustable, 4 Channel, PDSO24, LEAD FREE, TSSOP-24;
| 型号： | MIC2580A-1.6YTS-TR |
| 厂家： | 
MICROCHIP |
| 描述： | Power Supply Support Circuit, Adjustable, 4 Channel, PDSO24, LEAD FREE, TSSOP-24 光电二极管 |
| 文件： | 总21页 (文件大小：243K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC2580A
Micrel, Inc.
MIC2580A
Hot-Swap PCI Power Controller
General Description
Features
The MIC2580A is a hot-swap controller that provides for safe
andorderlyinsertionandremovalofPCIbasedadaptercards
from a PCI hot-plug compliant system backplane or
CompactPCI™ system.
• PCI hot-plug and CompactPCI™ hot-swap support
• +12V, +5V, +3.3V, and –12V power supply control
• Circuit breaker function to protect system
• Programmable slew rate control for all supplies
• Foldback current-limiting
The MIC2580A incorporates a circuit breaker function that
protects all four supplies (+12V, +5V, +3.3V, and –12V) upon
an overcurrent fault condition. Current foldback limiting pre-
vents large transient currents caused by plugging adapter
cards into live backplanes, such as in a CompactPCI system.
A programmable slew-rate control limits high inrush currents
to all loads that occur when power is applied to large capaci-
tive loads.
• +5V and +3.3V programmable current-limit thresholds
• Undervoltage and overcurrent diagnostic outputs
• Deglitch filters on diagnostic fault outputs
• Integrated +12V and –12V MOSFET switches
• Integrated high-side drivers for 3.3V and 5V external
switches
• Precharge supply for CompatPCI™ I/O termination
Applications
Voltage supervisory functions for all four power supplies are
provided by “power good” (/PWRGD) and “overcurrent fault”
(/FAULT) diagnostic outputs. Power good and overcurrent
fault include deglitch filters to prevent nuisance tripping.
Power good is active when all four supplies are within
tolerance. Fault (/FAULT) goes active upon overcurrent or
overtemperature conditions. The on-off control input (/ON) is
used to cycle power to the adapter card.
• PCI hot-plug systems
• CompactPCI™ hot-swap systems
Typical Application
10mΩ
IRF7413
IRF7413
1µF
10mΩ
MIC2580A
+12V
+5V
+12V/1A
+5V/8A
+3.3V/8A
GND
+12V
12VIN
5VIN
3VIN
12VOUT
5VSENSE
5VGATE
5VOUT
3VSENSE
3VGATE
3VOUT
VPCHG
/POR
+3.3V
GND
–12V
+5V
–12V/1A
1µF
+3.3V
VIO
VIO
1µF
1.2k
VPCH = +1V ±20%
VIO
(PRECHARGE SUPPLY)
/PCI_RST
/BD_SEL
/PCIRST
/ON
CRST
/PCIRST
/ON
Overcurrent
Fault
/LPCIRST
/FAULT
CSLEW
/EPWRGD
/PWRGD
CSTART
GND
/HEALTHY
/ENUM
/PGD
–12V
M12VIN M12VOUT
1µF
/LPCIRST
D0
D0
D1
D2
PCI
D1
D2
Controller
Dn
Dn
CompactPCI™ Adapter with Early Power
CompactPCI is a trademark of the PCI Industrial Computer Manufacturer’s Group.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
February 2005
1
MIC2580A
MIC2580A
Micrel, Inc.
Ordering Information
Part Number
Precharge
Voltage
Temperature
Range
Standard
Pb-Free
Package
MIC2580A-1.0BTS
MIC2580A-1.6BTS
MIC2580A-1.0YTS
MIC2580A-1.6YTS
1V
–40°C to +85°C
–40°C to +85°C
24-lead TSSOP
24-lead TSSOP
1.6V
Pin Configuration
12VOUT
3VGATE
3VOUT
3VSENSE
3VIN
/PCIRST
/LPCIRST
/EPWRGD
/PWRGD
1
2
3
4
5
6
7
8
9
24 12VIN
23 5VGATE
22 5VOUT
21 5VSENSE
20 5VIN
19 /FAULT
18 CSTART
17 CSLEW
16 /POR
VPCHG 10
GND 11
15 CRST
14 /ON
M12VIN 12
13 M12VOUT
24-lead TSSOP (TS)
Pin Function
Pin Description
Pin Number
Pin Name
12VOUT
3VGATE
1
2
+12V Switched Supply (Output): Load carrying output.
3.3V Gate Drive (Output): Drives gate of external N-channel MOSFET +3V
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.)
3
4
3VOUT
+3.3V Output Voltage Sense (Input): Connect to source of external
N-channel MOSFET (+3V switched output) to monitor for output undervolt-
age conditions.
+3.3V Current Sense (Input): Measures voltage drop across an external
sense resistor with respect to 3VIN for overcurrent detection through the
+3.3V switch.
3VSENSE
5
6
3VIN
3V Supply (Input): +3.3V-supply input for current monitoring (reference input
for 3VSENSE). Not a load-current carrying input.
/PCIRST
PCI-Bus Reset (Input): Input from PCI bus that resets the internal logic.
MIC2580A
2
February 2005
MIC2580A
Micrel, Inc.
Pin Number
Pin Name
/LPCIRST
Pin Function
7
Local PCI Reset (Open-Drain Output): Local PCI reset output to PCI
controller. Compliant to CompactPCI specification for LOCAL_PCI_RESET.
8
/EPWRGD
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 TFAIL per PCI Local Bus Specification, ver-
sion 2.1.
9
/PWRGD
VPCHG
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.)
10
Precharge Supply (Output): (MIC2580A-1.0) +1V ±20% supply used for
precharge bias for I/O terminations (CompactPCI only).
11
12
13
GND
M12VIN
M12VOUT
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.
14
/ON
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.
15
16
CRST
/POR
Reset Delay (External Component): Connect to external capactior (CRST) to
increase power-on reset delay.
Reset (Open-Drain Output): Active-low signal remains active for a time
determined by CRST after all supplies are within tolerance; i.e., /PWRGD is
active. This signal may be used as a reset for logic controllers.
17
18
19
CSLEW
CSTART
/FAULT
Slew (External Component): Connect to external capacitor (CSLEW) to
program the output slew rate of 3VGATE, 5VGATE, 12VGATE (internal) and
M12VGATE (internal).
Start-Up Timer (External Component): Connect to external capacitor
(CSTART) 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.
20
21
5VIN
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.
5VSENSE
22
23
5VOUT
+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.)
5VGATE
24
12VIN
12V Supply (Input): MIC2580A power supply and input for internal +12
switch. Supplies power for internal circuitry.
February 2005
3
MIC2580A
MIC2580A
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltages
Supply Voltages
+12V Input (V
) .................................................+14V
+12V Input (V
) ............................. +11.4V to +12.6V
12VIN
12VIN
+5V Input (V
).......................................................+7V
–12V Input (V
)........................... –11.4V to –12.6V
M12VIN
5VIN
+3.3V Input (V
–12V Input (V
)....................................................+7V
)...............................................–14V
+5V Input (V
)................................... +4.75V to +5.25
).............................. +3.125V to +3.5V
3VIN
5VIN
+3.3V Input (V
3VIN
M12VIN
/PWRGD, /FAULT, /POR, /EPWRGD, and /PCIRST
Temperature Range (T ) ........................... –40°C to +85°C
A
Output Current ...........................................................10mA
Junction Temperature (T ) ........................................ 150°C
J
Lead Temperature (Soldering)
Package Thermal Resistance (θ )
JA
Standard Package (-x.xBTS)
24-Lead TSSOP ..................................................83°C/W
IR Reflow......................................... 240°C + 0ºC/-5ºC
Lead-free Package (-x.xYTS)
IR Reflow......................................... 260ºC + 0ºC/-5ºC
ESD Rating, Note 3
ElHeucmtraincbaoldCy mhoadrealc..t..e...r.i..s..t..i.c...s................................. 2kV
V12VIN = 12V, V5VIN = 5V, V3VIN = 3.3V, VM12VIN = –12V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol
I12IN
I5IN
I3IN
I12MIN
VUVLO
Parameter
Supply Current
Condition
/ON > VIH
Min
Typ
2.2
4
0.23
3
Max
3
6
0.4
5
9.8
Units
mA
mA
mA
mA
V
mV
V
mV
V
Undervoltage Lockout
V12VIN increasing
8.9
-10.5
2.1
V12VIN UVLO hysteresis
VM12VIN decreasing
VM12VIN UVLO hysteresis
V5VIN increasing
V5VIN UVLO hysteresis
V3VIN increasing
300
100
20
-8.3
3.1
2.6
mV
V
2.4
V3VIN UVLO hysteresis
60
11
11
–40
6
–40
6
mV
V
V
µA
mA
µA
mA
V
mV
V
mV
V
mV
V
mV
V
V
V5VGATE
V3VGATE
I5VGATE
5VGATE Voltage
3VGATE Voltage
5VGATE Output Current
10.5
10.5
during start-up, V5VGATE = 5V
during turnoff; /FAULT = 0
during start-up, V5VGATE = 5V
during turnoff; /FAULT = 0
V12VOUT increasing
V12VOUT Power-Good hysteresis
VM12VOUT decreasing
VM12VOUT Power-Good hysteresis
V5VOUT increasing
V5VOUT Power-Good hysteresis
V3VOUT increasing
I3VGATE
VPGTH
3VGATE Output Current
Power Good Threshold Voltage
11
11.4
–10
4.7
3.10
0.8
1
200
50
–11.2
4.45
2.90
100
60
V3VOUT Power-Good hysteresis
logic low
logic high
VIL
VIH
IIL
Input Voltage Level (/ON)
2.0
–1
Input Leakage Currnet (/ON)
µA
MIC2580A
4
February 2005
MIC2580A
Micrel, Inc.
Symbol
VOL
Parameter
Condition
IOL = 2mA
Min
Typ
Max
0.4
Units
V
Output-Low Voltage
(/PWRGD, /FAULT, /POR,
EPWRGD, /LPCIRST)
TOV
Overtemperature Shutdown
TJ increasing
TJ decreasing
170
160
˚C
˚C
Threshold
ICRST
CRST Charge Current
during turn-on
during turn-on
during turn-on
–9
–9
–30
–11.5
–11.5
–45
600
600
100
300
67
µA
µA
µA
mΩ
mΩ
µA
µA
mV
mV
A
ICSTART
ICSLEW
RDS(on)12
RDS(on)M12
CSTART Charge Current
CSLEW Charge Current
Output MOSFET Resistance
–39
450
430
+12V internal MOSFET, IDS = 500mA
–12V internal MOSFET, IDS = 200mA
+12V internal MOSFET
–12V internal MOSFET
V5VIN – V5VSENSE
V3VIN – V3VSENSE
+12V internal MOSFET, ramped load
–12V internal MOSFET, ramped load
Output MOSFET Leakage
–100
0
45
45
1.0
–0.4
VCLTH
Current Limit Threshold Voltage
56
55
1.3
–0.5
67
1.5
–0.7
ILIM12
ILIM12M
Current-Limit
Threshold
A
Short-Circuit Current
+12V internal MOSFET, VOUT = 0V
140
mA
–12V internal MOSFET, VOUT = 0V
–170
mA
VPOR(thr)
VPCH
Power-On Reset Threshold Voltage
Precharge Bias Supply
2.4
1.0
1.6
2.4
V
V
V
V
MIC2580A-1.0, IPCH = 10mA
MIC2580A-1.6, IPCH = 10mA
0.8
1.28
1.2
1.92
VSTART
Start-up Threshold Voltage
AC Parameters
tGOOD
Early Power-Good
See Figure 4
See Figure 4
200
100
ns
ns
Response Low
t/GOOD
Early Power-Good
Response High
Undervoltage to Power-Good Delay
Current-limit to Fault Delay
20
20
7
µs
µs
µs
+5V Current-Limit-to-Off Delay
V
V
SENSE = 10mΩ
SENSE = 10mΩ
Note 4
+3.3V Current-Limit-to-Off Delay
7
µs
µs
µs
Note 4
+12V Current-Limit-to-Off Delay
+12V
–12V
25
25
Note 4
–12V Current-Limit-to-Off Delay
Note 4
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
Note 4. Off refers to the condition in which the circuit breaker turns all outputs off.
February 2005
5
MIC2580A
MIC2580A
Micrel, Inc.
Timing Diagrams
/ON
/ON
+5V
5VOUT
0V
+5V
5VOUT
0V
Short Circuit
+3.3V
+3.3V
3VOUT
3VOUT
0V
0V
+12V
+12V
12VOUT
12VOUT
0V
0V
0V
0V
M12VOUT
M12VOUT
–12V
–12V
/PWRGD
/PWRGD
tSTART
/FAULT
/POR
/FAULT
/POR
tRESET
Figure 1. Controller Timing: Normal Cycle
Figure 2. Controller Timing: Enable Into Short
Circuit Breaker
Reset
/ON
+5V
Fault
5VOUT
0V
+3.3V
3VOUT
0V
+12V
12VOUT
0V
0V
VIN
M12VOUT
VPGTH
}
1V
–12V
t/good
tgood
+5V
/EPWRGD
0V
/PWRGD
/FAULT
Figure 3. Controller Timing: Short on 5V
Figure 4. Early Power Good Response Time
MIC2580A
6
February 2005
MIC2580A
Micrel, Inc.
Typical Characteristics
Power-On
Output Rise Time vs.
Start-Up
Time
Reset Time
Slew-Rate Capacitance
-3
-3
-3
-3
-3
100x10
100x10
100x10
10x10
-3
10x10
10x10
-3
1x10
-3
-3
1x10
1x10
-6
-6
100x10
-6
-6
100x10
100x10
0.0001
10x10
0.001
0.01
(µF)
0.1
0.001
0.01
(µF)
0.1
0.0001
0.001
0.01
(µF)
0.1
C
C
C
START
POR
SLEW
February 2005
7
MIC2580A
MIC2580A
Micrel, Inc.
Functional Characteristics
10mΩ IRF7413
IRF7413
10mΩ
MIC2580A
12VOUT
+12V
+5V
12VIN
5VIN
3VIN
C12L
C5L
C3L
R12L
R5L
R3L
5VSENSE
5VGATE
5VOUT
3VSENSE
3VGATE
3VOUT
VPCHG
/POR
+3.3V
+5V
2.2k 2.2k
CRST
2.2k 2.2k
/PCIRST
/ON
CRST
/LPCIRST
/FAULT
CSLEW
CSLEW
CSTART
/EPWRGD CSTART
/PWRGD
GND
–12V
M12VIN M12VOUT
CM12L
RM12L
Functional Test Circuit
MIC2580A
8
February 2005
MIC2580A
Micrel, Inc.
3V and 5V
Gate-Voltage Response
C
RST = 0.01µF
SLEW = 0.03µF
V
/ON
C
(5V/div)
CSTART = 0.01µF
V
CSLEW
(5V/div)
V
3VGATE
(5V/div)
V
5VGATE
(5V/div)
Time (2.5ms/div)
Power-On
Reset Response
CRST = 0.01µF
V
/ON
(10V/div)
V
/PWRGD
(5V/div)
V
CRST
(2V/div)
tRESET = 2.6ms
V
/POR
(5V/div)
Time (1ms/div)
Power-Good
Response
V
/EPWRGD
(5V/div)
V
/PWRGD
(5V/div)
Time (10µs/div)
February 2005
9
MIC2580A
MIC2580A
Micrel, Inc.
CRST = 0.01µF
Fault Response
V
/ON
(10V/div)
Pull /FAULT Low
V
/FAULT
(10V/div)
V
3VOUT
(5V/div)
V
5VOUT
(5V/div)
V
12VOUT
(10V/div)
V
M12VOUT
(10V/div)
Time (10ms/div)
MIC2580A
10
February 2005
MIC2580A
Micrel, Inc.
Turn-On and Turn-off
CSTART = 0.01µF
V
/ON
C
SLEW = 0.03µF
(10V/div)
CRST = 0.01µF
V
3VOUT
(5V/div)
V
5VOUT
(5V/div)
V
12VOUT
(10V/div)
V
M12VOUT
(10V/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (2.5ms/div)
-12V Turn-On
CSTART = 0.01µF
V
/ON
C
SLEW = 0.07µF
(10V/div)
CRST = 0.01µF
V
C
M12L = 1µF
M12L = 80Ω
CSTART
(5V/div)
R
V
M12VOUT
(10V/div)
I
M12VIN
150mA
(100mA/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (2.5ms/div)
February 2005
11
MIC2580A
MIC2580A
Micrel, Inc.
3V Turn-On
V
CSTART = 0.01µF
SLEW = 0.03µF
/ON
(10V/div)
C
CRST = 0.01µF
C3L = 100µF
3L = 2.2Ω
V
CSTART
R
(5V/div)
V
3VOUT
1.5A
(2V/div)
I
3VIN
0.6A/ms
(1A/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (2.5ms/div)
5V Turn-On
CSTART = 0.01µF
SLEW = 0.03µF
V
/ON
C
(10V/div)
CRST = 0.01µF
C5L = 100µF
5L = 3.3Ω
V
CSTART
R
(5V/div)
V
5VOUT
1.5A
(5V/div)
I
5VIN
0.375A/ms
(1A/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/diV)
Time (2.5ms/div)
MIC2580A
12
February 2005
MIC2580A
Micrel, Inc.
12V Turn-On
CSTART = 0.01µF
SLEW = 0.04µF
V
/ON
C
(10V/div)
CRST = 0.01µF
C12L = 1µF
12L = 80Ω
V
CSTART
R
(5V/div)
V
12VOUT
150mA
(10V/div)
I
12VIN
(100mA/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Enable Into
-12V Output Short Circuit
CSTART = 0.01µF
V
/ON
C
C
R
C
SLEW = 0.01µF
RST = 0.01µF
12L = 100Ω
12L = 1µF
(10V/div)
V
CSTART
(5V/div)
M12VOUT = GND
V
3VOUT
(5V/div)
V
5VOUT
(5V/div)
V
12VOUT
(10/div)
V
M12VOUT
(10V/div)
I
M12VIN
(200mA/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (1ms/div)
February 2005
13
MIC2580A
MIC2580A
Micrel, Inc.
Enable Into
3V Output Short Circuit
CSTART = 0.01µF
V
/ON
(10V/div)
CSLEW = 0.01µF
CRST = 0.01µF
3VOUT = GND
R12L = 100Ω
V
CSTART
(5V/div)
C
R
C
12L = 1µF
V
3VOUT
(5V/div)
M12L = 100Ω
M12L = 1µF
I
3VIN
(1A/div)
V
5VOUT
(5V/div)
V
12VOUT
(10V/div)
V
M12VOUT
(10V/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (1ms/div)
Enable Into
5V Output Short Circuit
CSTART = 0.01µF
SLEW = 0.01µF
V
/ON
C
(10V/div)
CRST = 0.01µF
R
C
R
C
12L = 100Ω
V
CSTART
12L = 1µF
(5V/div)
M12L = 100Ω
M12L = 1µF
V
3VOUT
(5V/div)
5VOUT = GND
V
5VOUT
(5V/div)
I
5VIN
(200mA/div)
V
12VOUT
(10V/div)
V
M12VOUT
(10V/div)
V
/PWRGD
(5V/div)
(5V/div)
V
/POR
V
/FAULT
(5V/div)
MIC2580A
14
February 2005
MIC2580A
Micrel, Inc.
Enable Into
12V Output Short Circuit
V
CSTART = 0.01µF
CSLEW = 0.01µF
CRST = 0.01µF
/ON
(10V/div)
C
R
C
12L = 1µF
V
CSTART
M12L = 100Ω
M12L = 1µF
(5V/div)
V
3VOUT
(5V/div)
12VOUT = GND
V
5VOUT
(5V/div)
V
12VOUT
(10V/div)
I
12VIN
(500MA/div)
V
M12VOUT
(10V/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Start-up Blanking Response
CSTART = 0.01µF
V
/ON
(10V/div)
C
SLEW = 0.01µF
CRST = 0.01µF
V
CSTART
(5V/div)
V
5VOUT
Short Removed
(5V/div)
I
5VIN
(200mA/div)
V
/PWRGD
(5V/div)
V
/POR
(5V/div)
V
/FAULT
(5V/div)
Time (1ms/div)
February 2005
15
MIC2580A
MIC2580A
Micrel, Inc.
Circuit Breaker
Reset Response
New Start Cycle
CSTART = 0.01µF
SLEW = 0.01µF
CRST = 0.01µF
ON#
(10V/div)
C
Circuit Breaker
3VOUT
(5V/div)
Short Circuit
5VOUT
(5V/div)
12VOUT
(10V/div)
M12VOUT
(10V/div)
PWRGD#
(5V/div)
FAULT#
(5V/div)
POR#
(5V/div)
Time (10ms/div)
MIC2580A
16
February 2005
MIC2580A
Micrel, Inc.
Functional Diagram
12VIN
5VIN
3VIN
12VOUT
12V
Switch
R5SNS
Q5OUT
5VSENSE
5VGATE
5VOUT
5V
Switch
Control
R3SNS
Q3OUT
3VSENSE
3VGATE
3VOUT
3.3V
Switch
Control
VPCHG
Precharge
Supply
CSLEW
CSLEW
/POR
Slew
Control
Reset
CRST
CRST
Current
Limit
Thermal
Shutdown
/FAULT
CSTART
Control Logic
and
/ON
tD = 20µs
(delay)
Power Good
CSTART
/EPWRGD
/PWRGD
tD = 20µs
(delay)
/LPCIRST
M12VOUT
/PCIRST
M12VIN
–12V
Switch
MIC2580A
GND
February 2005
17
MIC2580A
MIC2580A
Micrel, Inc.
Thermal Shutdown
Functional Description
The+12Vand–12VinternalMOSFETswitchesareprotected
by current limit and overtemperature shutdown circuitry.
When the die temperature exceeds 160°C, /FAULT is as-
serted and all supplies are shut off. The power dissipated in
the MIC2580A is primarily due to the sum of current flowing
through the internal MOSFET switches and, to a lesser
extent, power dissipated due to the supply current. To com-
pute the total power dissipation of the MIC2580A the follow-
ing equation is used:
Start-Up Sequence
The start-up sequence iniates after all four supplies are
connected to the inputs and then /ON is asserted by
transistioning from high to low. During the start-up sequence,
all four gates ramp up at a rate determined by C
. During
SLEW
this time /PWRGD is deasserted until all four supplies are
withinspecifiedlevels.When/PWRGDisassertedthepower-
on-resetsignal/POR timerbegins. Thetimeperiodisdefined
by C
. Refer to Figure 1 for a timing diagram of the signals
RST
P
= P
+ P
+ P
D(supplies)
D(total)
D(+12V switch)
D(–12V switch)
during the start-up sequence.
where:
During the start-up sequence, a current source charges
2
P
= R
× I
DS(on) OUT
SUPPLY SUPPLY
C
at a constant rate until a threshold voltage of 2.4V is
D(switches)
D(supplies)
START
reached. This period of time defines an interval during which
overcurrent events are ignored. This prevents high inrush
currents that normally occur when charging capacitance
erroneously asserting /FAULT. The magnitude of the start-
P
= V
× I
To relate this to operating junction temperature:
T = P × θ + T
A
J
D
JA
where:
up time, t
is defined by C
.
START
START
T = ambient temperature
A
JA
The MIC2580A employs foldback current limiting that en-
suresthedevicestartsupincurrentlimit. Thisminimizeshigh
inrush currents due to ramping a voltage into capacitance
regardless of the size of the load capacitance.
θ
= package thermal resistance
Precharge Voltage
For CompactPCI applications, the MIC2580A-1.0BSM/BTS
integrates a 1V ±20% voltage source that satisfies
CompactPCI precharge requirements. The voltage source
can provide up to 10mA. For higher current, the MIC2580A-
1.6BSM/BTS integrates a 1.6V ±20% voltage source to bias
a NPN transistor.
Overcurrent Detection
The MIC2580A senses overcurrent via the use of external
sense resistors for the 5V and 3.3V supply rails. When the
sense voltage across these resistors is greater than or equal
to 50mV an overcurrent condition is detected. Therefore the
overcurrentsetpointisdeterminedbyI
=50mV/R
.
SENSE
+5V
LIMIT
For the +12V and –12V supply rails overcurrent detection is
set internally at 1.3A and –0.5A respectively.
R
MIC2580A-1.6
When an overcurrent condition is detected /FAULT is as-
serted only if the overcurrent condition lasts for a minimum
time period of 10µs. This delay prevents spurious noise from
the system erroneously tripping the circuit breaker and as-
serting /FAULT. Upon /FAULT being asserted an internal
latch is set that immediately turns off all four supplies to
preventfurtherdamagetothesystem.Toggling/ONwillreset
the latch and initiate another start-up sequence. Figures 2
and 3 depict the timing for two fault conditions.
VPCHG
I > 10mA
DATA
BUS
Figure 5. Voltage Source
Turnoff
Deasserting /ON will turn off all four supplies. Alternatively
driving /FAULT low will turn off all supplies but will not latch
the supplies off. Releasing /FAULT will initiate a new start
sequence.
MIC2580A
18
February 2005
MIC2580A
Application Information
Micrel, Inc.
must also be added to the dc voltage drop across the
MOSFET to compute total loss. In addition to meeting the
voltageregulationspecifications,thermalspecificationsmust
also be considered. During normal operation very little power
Whenever voltage is applied to a highly capacitive load, high
inrush currents may result in voltage droop that may bring the
supply voltage out of regulation for the duration of the
transient. The MIC2580A solves this problem by specifically
controlling the current and voltage supply ramps so that the
system supply voltages are not disturbed. Very large capaci-
tive loads are easily supported with this device.
should be dissipated in the MOSFET. DC power dissipation
2
of the MOSFET is easily computed as I R where I is the
DS
drain current and R is the specified on-resistance of the
DS
MOSFET at the expected operating drain current. However,
during excessive drain current or short-circuit faults, the
power dissipation in the external MOSFET will increase
dramatically. To help compute the effective power dissipated
during such transients, MOSFET manufacturers provide
transient thermal impedance curves for each MOSFET.
These curves provide the effective thermal impedance of the
MOSFET under pulsed or repetitive conditions; for example,
as will be the case when enabling into a short circuit fault.
From these curves the effective rise in junction temperature
of the MOSFET for a given condition can be computed. The
equation is given as:
Figure 1 shows the timing during turn-on. When /ON is forced
low,allsuppliesareturnedonataslewratedeterminedbythe
external capacitor, C
.
SLEW
Figure 2 shows the foldback characteristics for the supply
voltages. This foldback affect bounds the magnitude of the
current step when the supplies are turned on or shorted. This
specifies the compact PCI specification of 1.5A/ms, thereby
ensuring reliable operation. In discrete FET implementa-
tions, this magnitude can exceed several amps and may
cause the main supply to go out of regulation during this
transient event. This, in turn, could cause the system to
behave unpredictably. In addition, should a fault occur, the
MIC2580A will prevent system malfunctions by limiting the
current to within specifications.
peak T = PDM × Z
+ T
A
J
θJA
where PDM is the power dissipated in the MOSFET usually
computed as V x I
and Z
is the thermal response
θJA
IN
DRAIN
factor provided from the curves. Since the MIC2580A re-
ducesthecurrentto30%offullscaleevenunderseverefaults
such as short-circuits the MOSFET power dissipation is held
to safe levels. This feature allows MOSFETs with smaller
packages to be used for a given application thereby reducing
cost and PCB real-estate requirements.
MOSFET Selection
The external MOSFET should be selected to provide low
enough dc loss to satisfy the application’s voltage regulation
requirements. Notethatthevoltageacrossthesenseresistor
10mΩ
IRF7413
IRF7413
10mΩ
Power
MIC2580A
12VOUT
Supply
12V
5V
12V/500mA
5V/5A
12VIN
5VIN
3VIN
+12V
5VSENSE
5VGATE
5VOUT
3VSENSE
3VGATE
3VOUT
VPCHG
/POR
+5V
+3.3V
GND
–12V
3.3V/7.6A
3.3V
+5V
GND
CRST
/PCIRST
/ON
PCI Hot-Plug
Controller
/LPCIRST
/FAULT
CSLEW
/EPWDGD
/PWDGD
CSTART
GND
–12V
–12V /100mA
/CIRST
M12VIN M12VOUT
/CIRST
BUS EN
/CIRST
D0
D0
D1
D2
D1
D2
Bus
Switch
Dn
Dn
Figure 6. Hot-Plug PCI Application
February 2005
19
MIC2580A
MIC2580A
Micrel, Inc.
CompactPCI™ BD_SEL# Pin Tied to Ground
PCB Layout Considerations
For applications that use system backplanes with the
BD_SEL# pin tied to ground, the MIC2580A /ON pin is edge
sensitive. Therefore, the /ON pin requires a delay circuit for
proper start-up when the board has already been inserted
into the backplane and the supplies are switched off, then
back on. The circuit, shown in the figure below, allows the
MIC2580A /ON pin to transition from high to low which is
necessary for start-up. The delay time may be increased or
decreased by changing the RC time constant in the circuit,
but the delay time must exceed the ramp time of all system
backplane supplies. The same circuit is functional for hot
swap insertion.
To achieve accurate current sensing Kelvin connections are
recommended between the supply pin and the respective
sense resistor as shown in Figure 8. PCB trace length should
be kept at a minimum. 0.02 inches per ampere is a minimum
width for 1 oz. copper to prevent damage to traces carrying
high current. Keep these high-current traces as short as
possible.
short-length, high-current
(wide) copper traces
sense resistor
from
to
supply
load
Kelvin
connections
MIC2580A
2k
/FAULT
VIO
to
VIN SENSE
pin pin
to
(3.3V or 5V)
2k
/RESET
/ON
Figure 8. Layout Recommendation
1N914
50k
On PCB
10k
1.2k
2N3904
BD_SEL#
3.3µF
Figure 7. /ON Pin Assertion Delay Circuit
MIC2580A
20
February 2005
MIC2580A
Micrel, Inc.
Package Information
4.50 (0.177)
4.30 (0.169)
DIMENSIONS:
MM (INCH)
6.4 BSC (0.252)
0.30 (0.012)
0.19 (0.007)
7.90 (0.311)
7.70 (0.303)
1.10 MAX (0.043)
0.20 (0.008)
0.09 (0.003)
0.65 BSC
(0.026)
1.00 (0.039) REF
8°
0°
0.15 (0.006)
0.05 (0.002)
0.70 (0.028)
0.50 (0.020)
24-Lead TSSOP (TS)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2001 Micrel Incorporated
February 2005
21
MIC2580A
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