LTC4241
PCI-Bus with 3.3V Auxiliary
Hot Swap Controller
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FEATURES
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DESCRIPTIO
The LTC®4241 is a Hot Swap controller that allows a board
to be safely inserted and removed from a live PCI-bus slot.
It has a primary controller that controls the four PCI
supplies and an independent auxiliary controller to control
the 3.3V auxiliary supply. External N-channel transistors
are used to control the 3.3V, 5V and 3.3V auxiliary supplies
while on-chip switches control the –12V and 12V supplies.
The 3.3V, 5V and 3.3V auxiliary supplies can be ramped up
at an adjustable rate. Electronic circuit breakers protect all
five supplies against overcurrent faults. The foldback
current limit feature reduces current spikes and power
dissipation when shorts occur. The PWRGD output of the
primary controller indicates when all four PCI supplies are
within tolerance. The FAULT output indicates an overcurrent
condition for any of the five supplies.
Allows Safe Board Insertion and Removal from a
Live PCI Slot
Controls 3.3V, 5V, –12V, 12V and 3.3V Auxiliary
Supplies
Independent 3.3V Auxiliary Supply Hot SwapTM
Controller
Adjustable Foldback Current Limit with Circuit
Breaker
Adjustable Supply Voltage Power-Up Rate
High Side Drive for External N-Channel FETs
–12V and 12V On-Chip Switches
Fault and Power Good Outputs
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APPLICATIO S
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PCI-Based Servers
Computer Systems
The LTC4241 is available in the 20-pin narrow SSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
GND
R1
0.007Ω
R2
0.005Ω
R3
0.07Ω
SYSTEM
POWER
SUPPLY
11
8
1
2
12
5
R8 10k
PCI
POWER
SYSTEM
CONTROLLER
6
R9 10k
7
10
5V
5A
R4
10Ω
Q2
IRF7413
R5
10Ω
Q3
Si2306DS
C3
10nF
Q1
IRF7413
3.3VAUX
500mA
R7
100Ω
C1
0.047µF
R6
10Ω
9
13
14
15
AUXIN AUXSENSE AUXGATE 3VIN 3VSENSE GATE
3.3V
7.6A
3
3VOUT
17
16
18
5VIN 5VSENSE 5VOUT
GND
12VIN
VEEIN
12VOUT
AUXON
ON
FAULT
LTC4241
VEEOUT
TIMER
PWRGD
20
12V
500mA
19
–12V
100mA
4
BACKPLANE
CONNECTOR
C2
0.1µF
LOGIC
RESET
RESET
4241 F01
Figure 1. Hot Swappable PCI and 3.3V Auxiliary Supplies
sn4241 4241f
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LTC4241
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltages
12VIN ................................................................... 14V
VEEIN .................................................................. –14V
AUXIN ................................................................... 7V
Input Voltage
ON ......................................................... –0.3V to 14V
AUXON .................................................. –0.3V to 14V
Output Voltages
(FAULT, PWRGD) .................................. –0.3V to 14V
Analog Voltages
TIMER, 3VIN, 3VSENSE, GATE,
5VSENSE, 5VIN ............................. –0.3V to (12VIN + 0.3V)
3VOUT, 5VOUT ........................................ –0.3V to 14V
AUXSENSE .......................... –0.3V to (AUXIN + 0.3V)
VEEOUT ................................................ –14V to + 0.3V
12VOUT .................................................. –0.3V to 14V
AUXGATE ......................... Internally Limited (Note 3)
Operating Temperature Range
LTC4241CGN ........................................... 0°C to 70°C
LTC4241IGN ........................................–40°C to 85°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering,10sec).................... 300°C
ORDER PART
NUMBER
LTC4241CGN
LTC4241IGN
TOP VIEW
12VIN
1
20 12VOUT
VEEIN
2
19 VEEOUT
3VOUT
3
18 5VOUT
TIMER
4
17 5VIN
ON
5
16 5VSENSE
FAULT
6
15 GATE
PWRGD
7
14 3VSENSE
GND
8
13 3VIN
AUXGATE
9
12 AUXON
AUXSENSE 10
11 AUXIN
GN PACKAGE
20-LEAD NARROW PLASTIC SSOP
TJMAX = 150°C, θJA = 135°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V12VIN = 12V, VVEEIN = –12V, V3VIN = 3.3V, V5VIN = 5V,
VAUXIN = 3.3V. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
IDD
V12VIN Supply Current
VAUXIN Supply Current
ON = V12VIN
AUXON = VAUXIN
●
●
VLKO
Undervoltage Lockout,
Low-to-High Transition
12VIN
3VIN
5VIN
AUXIN
●
●
●
●
VLKH
Undervoltage Lockout Hysteresis
3VIN, 5VIN
AUXIN
VSENSE5(TH)
Current Limit Sense Voltage
Threshold (V5VIN – V5VSENSE)
V5VOUT = 0V
V5VOUT > 4V
●
●
5.5
40
9
55
14.5
70
mV
mV
VSENSE3(TH)
Current Limit Sense Voltage
Threshold (V3VIN – V3VSENSE)
V3VOUT = 0V
V3VOUT > 2V
●
●
5.5
40
9
55
14.5
70
mV
mV
tCB
Circuit Breaker Trip Filter Time
(V5VIN – V5VSENSE) = Step 0 to 100mV
(VAUXIN – VAUXSENSE) = Step 0 to 100mV
IGATE
GATE Pin Output Current
ON High, FAULT High, VGATE = GND
ON Low, FAULT High, VGATE = 5V
ON High, FAULT Low, VGATE = 5V
6.5
2.25
3.65
2.35
TYP
MAX
UNITS
2.5
0.5
8
1.5
mA
mA
9
2.50
3.90
2.60
10.8
2.75
4.15
2.85
V
V
V
V
20
120
mV
mV
µs
µs
17
8
●
–20
5
–60
200
25
–100
35
µA
µA
mA
sn4241 4241f
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LTC4241
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V12VIN = 12V, VVEEIN = –12V, V3VIN = 3.3V, V5VIN = 5V,
VAUXIN = 3.3V. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
∆VGATE
External Gate Voltage
(V12VIN – VGATE)
VDROP
Internal Switch Voltage Drop
ICL(12)
MIN
TYP
MAX
UNITS
●
100
200
mV
(V12VIN – V12VOUT), I12VOUT = 500mA
(VEEOUT – VVEEIN), IVEEIN = 100mA
●
●
200
120
600
250
mV
mV
Current Limit
12VIN = 12V, 12VOUT = 0V, TIMER = GND
12VIN = 12V, 12VOUT = 11V, TIMER = GND
●
●
–50
–525
–300
–850
–575
–1500
mA
mA
ICL(VEE)
Current Limit
VEEIN = –12V, VEEOUT = 0V, TIMER = GND
VEEIN = –12V, VEEOUT = –11V, TIMER = GND
●
●
50
250
200
450
425
750
mA
mA
TTS
Thermal Shutdown Temperature
VPG(TH)
Power Good Threshold Voltage
V12VOUT Rising
VVEEOUT Falling
V3VOUT Rising
V5VOUT Rising
●
●
●
●
10.8
–10.2
2.8
4.5
11.1
–10.5
2.9
4.65
VPGH
Power Good Hysteresis
3VOUT
5VOUT
12VOUT, VEEOUT
VIL
Input Low Voltage
ON, AUXON
●
VIH
Input High Voltage
ON, AUXON
●
VOL
Output Low Voltage
FAULT, PWRGD , IOL = 3mA
●
IIN
AUXON Pin Input Current
AUXON = GND
AUXON = VAUXIN
●
●
ON Pin Input Current
ON = GND
ON = V12VIN
5VSENSE Input Current
11.4
–10.8
3.0
4.78
20
30
50
V
V
V
V
mV
mV
mV
0.8
V
2
V
0.4
V
±0.08
±0.08
±10
±10
µA
µA
●
●
±0.08
±0.08
±10
±10
µA
µA
5VSENSE = 5V
●
50
100
µA
3VSENSE Input Current
3VSENSE = 3V
●
50
100
µA
5VIN Input Current
5VIN = 5V
●
580
900
µA
3VIN Input Current
3VIN = 3V
●
310
550
µA
5VOUT Input Current
5VOUT = 5V, ON = V12VIN
●
260
500
µA
●
150
350
µA
3VOUT Input Current
3VOUT = 3V, ON = V12VIN
RDIS
5VOUT Discharge Impedance
3VOUT Discharge Impedance
12VOUT Discharge Impedance
VEEOUT Discharge Impedance
ON = GND
ON = GND
ON = GND
ON = GND
ITIMER
TIMER Pin Current
Timer On, VTIMER = GND,
Timer Off, VTIMER = 5V,
VTIMER
VAUXCB
°C
150
Ω
Ω
Ω
Ω
60
50
450
1600
●
–15
–22
45
–27
µA
mA
TIMER Threshold Voltage
(V12VIN – VTIMER)
●
0.5
0.9
1.3
V
Circuit Breaker Trip Voltage
(VAUXIN – VAUXSENSE)
●
40
50
60
mV
IAUXGATE
AUXGATE Gate Output Current
AUXON High, FAULT High, VAUXGATE = GND
AUXON Low, FAULT High, VAUXGATE = 5V
AUXON High, FAULT Low, VAUXGATE = 10V
●
–6
–10
200
50
–14
µA
µA
mA
∆VAUXGATE
External AUXGATE Gate Voltage
(VAUXGATE – VAUXIN), VAUXIN = 3.3V
●
5
8
11
V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2 : All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 3 : An internal zener on the AUXGATE pin clamps the charge pump
voltage to a typical maximum operating voltage of 12V. External overdrive
of the AUXGATE pin beyond the internal zener voltage may damage the
device.
sn4241 4241f
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LTC4241
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TYPICAL PERFOR A CE CHARACTERISTICS
3.3V and 5V Current
Foldback Profile
4
3VIN = 3.3V
5VIN = 5V
RSENSE = 0.005Ω
0.5
800
700
600
500
400
300
1.5
2.5
3.5
4.5
OUTPUT VOLTAGE (V)
0
1
2
12VIN Current Limit
vs Temperature
40
30
20
5VOUT = 0V
1200
60
3VOUT = 3.3V
1000
50
CURRENT LIMIT (mA)
CURRENT LIMIT VOLTAGE (mV)
CURRENT LIMIT VOLTAGE (mV)
50
40
30
20
3VOUT = 0V
10
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
100
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G07
12VOUT = 0V
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G06
GATE, AUXGATE Output Source
Current vs Temperature
54
GATE OUTPUT SOURCE CURRENT (µA)
CIRCUIT BREAKER TRIP VOLTAGE (mV)
VEEOUT = 0V
400
53
52
51
50
49
48
47
46
45
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G08
90
12.5
80
12.0
11.5
70
GATE
60
11.0
50
10.5
40
10.0
AUXGATE
30
9.5
20
9.0
10
–75 –50 –25
AUXGATE OUTPUT SOURCE CURRENT (µA)
200
600
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
55
600
300
800
200
(VAUXIN – VAUXSENSE)
Circuit Breaker Trip Voltage
vs Temperature
400
12VOUT = 11V
4241 • G05
VEEIN Current Limit
vs Temperature
VEEOUT = –11V
0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10 –11 –12
OUTPUT VOLTAGE (V)
4241 • G03
3VIN Current Limit Voltage
vs Temperature
4241 • G04
CURRENT LIMIT (mA)
300
4241 • G02
5VOUT = 5V
0
–75 –50 –25
400
0
3 4 5 6 7 8 9 10 11 12
OUTPUT VOLTAGE (V)
70
500
500
100
5.5
70
0
–75 –50 –25
600
200
5VIN Current Limit Voltage
vs Temperature
10
700
100
4241 • G01
60
800
200
0
VEEIN = –12V
900
OUTPUT CURRENT (mA)
6
0
1000
900
5VOUT
8
2
1100
12VIN = 12V
1000
3VOUT
OUTPUT CURRENT (mA)
OUTPUT CURRENT (A)
10
–12V Current Foldback Profile
12V Current Foldback Profile
1100
12
8.5
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G09
sn4241 4241f
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LTC4241
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TYPICAL PERFOR A CE CHARACTERISTICS
GATE, AUXGATE Output Sink
Current vs Temperature
300
GATE
250
AUXGATE
150
100
50
–75 –50 –25
80
8.20
70
8.15
AUXIN = 3.3V
60
AUXGATE
50
40
GATE
30
20
10
10.85
300
275
250
225
200
175
150
125
100
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
Power Good Threshold Voltage
vs Temperature (12VOUT)
POWER GOOD THRESHOLD VOLTAGE (V)
POWER GOOD THRESHOLD VOLTAGE (V)
11.00
10.95
10.90
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G16
140
120
100
80
60
40
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
Power Good Threshold Voltage
vs Temperature (3VOUT)
2.915
4.67
4.66
4.65
4.64
4.63
4.62
4.61
4.60
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G15
4.68
11.05
160
Power Good Threshold Voltage
vs Temperature (5VOUT)
11.20
11.10
IVEEIN = 100mA
180
4241 • G14
4241 • G13
11.15
0 25 50 75 100 125 150
TEMPERATURE (°C)
200
I12VOUT = 500mA
POWER GOOD THRESHOLD VOLTAGE (V)
10.70
–75 –50 –25
7.85
VEE Internal Switch Voltage Drop
vs Temperature
INTERNAL SWITCH VOLTAGE DROP (mV)
INTERNAL SWITCH VOLTAGE DROP (mV)
AUXGATE VOLTAGE (V)
11.00
7.90
4241 • G12
325
11.15
7.95
12V Internal Switch Voltage Drop
vs Temperature
11.75
11.30
8.00
4241 • G11
AUXGATE Voltage vs Temperature
11.45
8.05
7.75
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G10
11.60
8.10
7.80
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
(VAUXGATE – VAUXIN) (V)
FAST PULL-DOWN CURRENT (mA)
OUTPUT SINK CURRENT (µA)
350
200
(VAUXGATE – VAUXIN)
vs Temperature
GATE, AUXGATE Fast Pull-Down
Current vs Temperature
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G17
2.910
2.905
2.900
2.895
2.890
2.885
2.880
2.875
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G18
sn4241 4241f
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LTC4241
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TYPICAL PERFOR A CE CHARACTERISTICS
Power Good Threshold Voltage
vs Temperature (VEEOUT)
Timer Threshold Voltage
vs Temperature
Timer Current vs Temperature
23.00
0.950
V12VIN – VTIMER
–10.55
–10.50
–10.45
–10.40
–10.35
–10.30
–75 –50 –25
0.925
22.75
0.900
22.50
TIMER CURRENT (µA)
TIMER THRESHOLD VOLTAGE (V)
0.875
0.850
0.825
0.800
21.00
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
12VIN Undervoltage Lockout
Threshold vs Temperature
700
9.20
650
2.8
5VIN
SUPPLY CURRENT (µA)
600
2.7
2.6
2.5
2.4
550
AUXIN
500
450
VEEIN
400
350
3VIN
300
2.3
250
2.2
–75 –50 –25
200
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
0 25 50 75 100 125 150
TEMPERATURE (°C)
5VIN Undervoltage Lockout
Threshold vs Temperature
3.825
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G25
(V5VIN – V5VSENSE) CIRCUIT BREAKER TRIP
FILTER TIME (µs)
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
3.850
9.00
8.95
8.90
8.85
8.80
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
2.625
AUXIN
2.600
2.575
2.550
2.525
2.500
3VIN
2.475
2.450
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G26
18.50
8.3
18.25
8.2
8.1
18.00
VAUXIN – VAUXSENSE
17.75
8.0
17.50
7.9
17.25
7.8
V5VIN – V5VSENSE
17.00
7.7
16.75
7.6
16.50
–75 –50 –25
7.5
0 25 50 75 100 125 150
TEMPERATURE (°C)
(VAUXIN – VAUXSENSE) CIRCUIT BREAKER TRIP
FILTER TIME (µs)
3.875
9.05
(V5VIN – V5VSENSE), (VAUXIN –
VAUXSENSE) Circuit Breaker Trip
Filter Time vs Temperature
2.650
3.900
9.10
4241 • G24
3VIN, AUXIN Undervoltage Lockout
Threshold vs Temperature
3.925
9.15
4241 • G23
4241 • G22
3.950
0 25 50 75 100 125 150
TEMPERATURE (°C)
4241 • G21
VEEIN, 5VIN, 3VIN, AUXIN Supply
Current vs Temperature
2.9
SUPPLY CURRENT (mA)
21.50
4241 • G20
12VIN Supply Current
vs Temperature
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
21.75
21.25
4241 • G19
3.800
–75 –50 –25
22.00
0.775
0.750
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
22.25
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
POWER GOOD THRESHOLD VOLTAGE (V)
–10.60
4241 • G27
sn4241 4241f
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LTC4241
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PI FU CTIO S
12VIN (Pin 1): 12V Supply Input. This pin powers the
primary controller internal circuitry. A 0.5Ω switch is
connected between 12VIN and 12VOUT with a foldback
current limit. An undervoltage lockout circuit prevents the
switches from turning on while the 12VIN pin voltage is
less than 9V.
VEEIN (Pin 2): –12V Supply Input. A 1.2Ω switch is
connected between VEEIN and VEEOUT with a foldback
current limit.
3VOUT (Pin 3): 3.3V Output Monitor. Used to monitor the
3.3V output supply voltage. The PWRGD signal cannot go
low until the 3VOUT pin exceeds 2.9V.
TIMER (Pin 4): Current Limit Fault Timer Input. Connect a
capacitor from TIMER to ground. With the primary controller turned off (ON = GND) or the internal circuit breaker
tripped due to a PCI supply fault (FAULT = low), the TIMER
pin is internally held at ground. When the primary controller is turned on, a 22µA pull-up current source is connected to TIMER. Current limit faults from the PCI supplies
will be ignored until the voltage at the TIMER pin rises to
within 0.9V of 12VIN.
ON (Pin 5): On Control Input. A rising edge turns on the
external N-channel FETs for 3.3V and 5V PCI supplies, the
internal 12V and –12V switches and a falling edge turns it
off. If the ON pin is cycled low then high following the trip
of the circuit breaker due to a PCI supply fault, the circuit
breaker is reset.
FAULT (Pin 6): Fault Output. Open drain logic output used
by both the primary and auxiliary controller to indicate an
overcurrent fault condition. When any of the PCI and 3.3V
auxiliary supplies are in current limit fault, the controller
detecting the fault (primary or auxiliary) will be latched off
and the FAULT pin will be pulled low. Current limit faults
from the PCI supplies are ignored while the voltage at the
TIMER pin is less than (12VIN – 0.9V). The current limit
fault detected by the primary controller will not cause the
auxiliary controller to latch off and vice versa.
PWRGD (Pin 7): Power Good Output. Open drain logic
output used by the primary controller to indicate the
voltage status of the PCI supplies. PWRGD remains low
while V12VOUT ≥ 11.1V, V3VOUT ≥ 2.9V, V5VOUT ≥ 4.65V,
VVEEOUT ≤ –10.5V. When one of the supplies falls below its
power good threshold voltage, PWRGD will go high after
a 15µs deglitching time. The switches will not be turned off
when PWRGD goes high.
GND (Pin 8): Chip Ground
AUXGATE (Pin 9): High Side Gate Drive for the 3.3V
Auxiliary External N-channel MOSFET. An internal charge
pump generates at least 8V of gate drive from a 3.3V
auxiliary supply. A zener clamps AUXGATE approximately
12V above the supply voltage at AUXIN. The rise time at
AUXGATE is set by an external AUXGATE capacitor connected to ground and an internal 10µA current source
provided by the charge pump. If the circuit breaker trips or
the auxiliary supply voltage hits the undervoltage lockout
threshold, a 50mA current sink rapidly pulls AUXGATE
low.
AUXSENSE (Pin 10): 3.3V Auxiliary Circuit Breaker Current Sense Input. The load current is monitored by a sense
resistor connected between AUXIN and AUXSENSE. The
circuit breaker trips if the voltage across the sense resistor
exceeds 50mV and the AUXGATE pin voltage will be turned
off.
AUXIN (Pin 11): 3.3V Auxiliary Supply Input. This pin
powers the auxiliary controller internal circuitry. An
undervoltage lockout circuit disables the AUXGATE pin
until the supply voltage at AUXIN is greater than 2.6V.
AUXGATE is held at ground potential until the undervoltage
lockout deactivates. If no 3.3V auxiliary supply is available,
tie AUXIN to ground.
AUXON (Pin 12): ON Control Input for Auxiliary Supply. A
rising edge turns on the external N-channel FET for 3.3V
auxiliary supply and a falling edge turns it off. If the AUXON
pin is cycled low then high following the trip of the circuit
breaker due to a 3.3V auxiliary supply fault, the circuit
breaker is reset.
3VIN (Pin 13): 3.3V Supply Sense Input. An undervoltage
lockout circuit prevents the switches from turning on
when the voltage at the 3VIN pin is less than 2.5V. If no 3.3V
input supply is available, tie 3VIN to the 5VIN pin.
3VSENSE (Pin 14): 3.3V Current Limit Set Pin. With a sense
resistor placed in the supply path between 3VIN and
3VSENSE, the GATE pin voltage will be adjusted to maintain
sn4241 4241f
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LTC4241
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PI FU CTIO S
a constant voltage across the sense resistor and a
constant current through the switch. A foldback feature
makes the current limit decrease as the voltage at the
3VOUT pin approaches ground. To disable the current limit,
3VSENSE and 3VIN can be shorted together.
GATE (Pin 15): High Side Gate Drive for the 3.3V and 5V
PCI Supplies External N-channel MOSFETs. Requires an
external series RC network for the current limit loop
compensation and setting the minimum ramp-up rate.
During power-up, the slope of the voltage rise at the GATE
is set by the internal 60µA pull up current source and the
external GATE capacitor connected to ground. During
power-down, the slope of the falling voltage is set by the
200µA current source connected to ground and the external GATE capacitor.
5VSENSE (Pin 16): 5V Current Limit Set Pin. With a sense
resistor placed in the supply path between 5VIN and
5VSENSE, the GATE pin voltage will be adjusted to maintain
a constant voltage across the sense resistor and a constant current through the switch. A foldback feature makes
the current limit decrease as the voltage at the 5VOUT pin
approaches ground. To disable the current limit, 5VSENSE
and 5VIN can be shorted together.
5VIN (Pin 17): 5V Supply Sense Input. Used to monitor the
5V input supply voltage. An undervoltage lockout circuit
prevents the switches from turning on when the voltage at
the 5VIN pin is less than 3.9V.
5VOUT (Pin 18): 5V Output Monitor. Used to monitor the
5V output supply voltage. The PWRGD signal cannot go
low until the 5VOUT pin exceeds 4.65V.
VEEOUT (Pin 19): –12V Supply Output. A 1.2Ω switch is
connected between VEEIN and VEEOUT. VEEOUT must
fall below –10.5V before the PWRGD signal can go low on
the LTC4241.
12VOUT (Pin 20): 12V Supply Output. A 0.5Ω switch is
connected between 12VIN and 12VOUT. 12VOUT must
exceed 11.1V before the PWRGD signal can go low on the
LTC4241
sn4241 4241f
8
LTC4241
W
BLOCK DIAGRA
5VIN
5VSENSE
GATE
3VSENSE
3VIN
17
16
15
14
13
+
–
5VOUT
60µA
+
55mV
+–
ON
5
PWRGD
7
+
–
12VIN
18
3VOUT
55mV
–
200µA
Q5
3.9V
UVL
3
+
A2
A1
–
3VOUT 5VOUT
Q8
Q7
–+
2.5V
UVL
CP1
+
Q3
–
REF
PRIMARY CONTROL LOGIC
FAULT
CP2
6
+
Q4
–
9V
UVL
REF
12VIN
Q9
REF
Q10
Q2
Q1
22µA
CP4
+
+
CP3
Q6
–
–
PCI-BUS HOT SWAP
CONTROLLER
REF
1
20
4
2
19
8
12VIN
12VOUT
TIMER
VEEIN
VEEOUT
GND
Q12
CHARGE
PUMP
AUXIN 11
+
–
50mV
+
8µs
FILTER
A3
AUXSENSE 10
–
AUXILIARY
CONTROL
LOGIC
10µA
9 AUXGATE
Q11
Z1
12V
2.6V
UVL
Z2
20V
200µA
AUXIN
AUXON 12
3.3V AUXILIARY SUPPLY
HOT SWAP CONTROLLER
4241 BD
sn4241 4241f
9
LTC4241
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U U
APPLICATIO S I FOR ATIO
Hot Circuit Insertion
When a circuit board is inserted into a live PCI slot, the
supply bypass capacitors on the board can draw huge
transient currents from the PCI power bus as they charge
up. The transient currents can cause permanent damage
to the connector pins and glitches the power bus, causing
other boards in the system to reset.
The LTC4241 is designed to turn a board’s supply voltages
on and off in a controlled manner, allowing the board to be
safely inserted or removed from a live PCI slot without
glitching the system power supplies. The chip also protects the PCI supplies from shorts and monitors the
supply voltages.
The LTC4241 is designed for motherboard applications
and includes an additional independent controller for the
3.3V auxiliary supply.
LTC4241 Feature Summary
8. Fault control: the current limit fault detected by either
the primary or auxiliary controller will not cause the other
controller to latch off. Both controllers use the FAULT
output to indicate a fault condition.
9. Space saving 20-pin narrow SSOP package.
PCI Power Requirements
PCI systems usually require four power rails: 5V, 3.3V,
–12V and 12V. Systems implementing the 3.3V signaling
environment are usually required to provide all four rails in
every system.
A 3.3V auxiliary supply is added in the PCI system to power
PCI logic functions that need to remain active when the
rest of the system is unpowered.
The tolerance of the supplies as measured at the components is summarized in Table 1.
Table 1. PCI Power Supply Requirements
1. Allows safe board insertion and removal from a
motherboard.
SUPPLY
TOLERANCE
CAPACITIVE
LOAD
5V
5V ± 5%
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