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LTC4241 PCI-Bus with 3.3V Auxiliary Hot Swap Controller
FEATURES
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DESCRIPTIO
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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
APPLICATIO S
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PCI-Based Servers Computer Systems
The LTC(R)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. 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.
TYPICAL APPLICATIO
R1 0.007
Q1 IRF7413
R2 0.005
Q2 IRF7413
SYSTEM POWER SUPPLY
R3 0.07
Q3 Si2306DS
R5 10
C3 10nF
R6 10 9 13 14 15 3 3VOUT 17 16 18
11 8 1 2 12 5 R8 10k PCI POWER SYSTEM CONTROLLER RESET 6 R9 10k 7 GND 12VIN VEEIN AUXON ON FAULT PWRGD
10
AUXIN AUXSENSE AUXGATE 3VIN 3VSENSE GATE
5VIN 5VSENSE 5VOUT 12V 500mA -12V 100mA BACKPLANE CONNECTOR C2 0.1F LOGIC RESET
4241 F01
12VOUT LTC4241 VEEOUT TIMER
Figure 1. Hot Swappable PCI and 3.3V Auxiliary Supplies
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GND 5V 5A R4 10 3.3V 7.6A 3.3VAUX 500mA R7 100 C1 0.047F 20 19 4
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LTC4241
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW 12VIN VEEIN 3VOUT TIMER ON FAULT PWRGD GND AUXGATE 1 2 3 4 5 6 7 8 9 20 12VOUT 19 VEEOUT 18 5VOUT 17 5VIN 16 5VSENSE 15 GATE 14 3VSENSE 13 3VIN 12 AUXON 11 AUXIN
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 ........................................... 0C to 70C LTC4241IGN ........................................-40C to 85C Storage Temperature Range ..................-65C to 150C Lead Temperature (Soldering,10sec).................... 300C
LTC4241CGN LTC4241IGN
AUXSENSE 10
GN PACKAGE 20-LEAD NARROW PLASTIC SSOP TJMAX = 150C, JA = 135C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
SYMBOL IDD VLKO PARAMETER V12VIN Supply Current VAUXIN Supply Current Undervoltage Lockout, Low-to-High Transition CONDITIONS
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V12VIN = 12V, VVEEIN = -12V, V3VIN = 3.3V, V5VIN = 5V, VAUXIN = 3.3V. (Note 2)
MIN
q q q q q q
TYP 2.5 0.5
MAX 8 1.5 10.8 2.75 4.15 2.85
UNITS mA mA V V V V mV mV
ON = V12VIN AUXON = VAUXIN 12VIN 3VIN 5VIN AUXIN 3VIN, 5VIN AUXIN V5VOUT = 0V V5VOUT > 4V V3VOUT = 0V V3VOUT > 2V (V5VIN - V5VSENSE) = Step 0 to 100mV (VAUXIN - VAUXSENSE) = Step 0 to 100mV 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
9 2.50 3.90 2.60 20 120
VLKH VSENSE5(TH) VSENSE3(TH) tCB IGATE
Undervoltage Lockout Hysteresis Current Limit Sense Voltage Threshold (V5VIN - V5VSENSE) Current Limit Sense Voltage Threshold (V3VIN - V3VSENSE) Circuit Breaker Trip Filter Time GATE Pin Output Current
q q q q
5.5 40 5.5 40
9 55 9 55 17 8
14.5 70 14.5 70
q
-20 5
-60 200 25
-100 35
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mV mV mV mV s s A A mA
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LTC4241
DC ELECTRICAL CHARACTERISTICS
SYMBOL VGATE VDROP ICL(12) ICL(VEE) TTS VPG(TH) PARAMETER External Gate Voltage Internal Switch Voltage Drop Current Limit Current Limit Thermal Shutdown Temperature Power Good Threshold Voltage CONDITIONS
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V12VIN = 12V, VVEEIN = -12V, V3VIN = 3.3V, V5VIN = 5V, VAUXIN = 3.3V. (Note 2)
MIN
q q q q q q q
TYP 100 200 120
MAX 200 600 250 -575 -1500 425 750 11.4 -10.8 3.0 4.78
UNITS mV mV mV mA mA mA mA C V V V V mV mV mV
(V12VIN - VGATE) (V12VIN - V12VOUT), I12VOUT = 500mA (VEEOUT - VVEEIN), IVEEIN = 100mA 12VIN = 12V, 12VOUT = 0V, TIMER = GND 12VIN = 12V, 12VOUT = 11V, TIMER = GND VEEIN = -12V, VEEOUT = 0V, TIMER = GND VEEIN = -12V, VEEOUT = -11V, TIMER = GND V12VOUT Rising VVEEOUT Falling V3VOUT Rising V5VOUT Rising 3VOUT 5VOUT 12VOUT, VEEOUT ON, AUXON ON, AUXON FAULT, PWRGD , IOL = 3mA AUXON = GND AUXON = VAUXIN ON = GND ON = V12VIN 5VSENSE = 5V 3VSENSE = 3V 5VIN = 5V 3VIN = 3V 5VOUT = 5V, ON = V12VIN 3VOUT = 3V, ON = V12VIN ON = GND ON = GND ON = GND ON = GND Timer On, VTIMER = GND, Timer Off, VTIMER = 5V,
-50 -525 50 250 10.8 -10.2 2.8 4.5
-300 -850 200 450 150 11.1 -10.5 2.9 4.65 20 30 50
q q q q
VPGH
Power Good Hysteresis
VIL VIH VOL IIN
Input Low Voltage Input High Voltage Output Low Voltage AUXON Pin Input Current ON Pin Input Current 5VSENSE Input Current 3VSENSE Input Current 5VIN Input Current 3VIN Input Current 5VOUT Input Current 3VOUT Input Current
q q q q q q q q q q q q q
0.8 2 0.4 0.08 0.08 0.08 0.08 50 50 580 310 260 150 60 50 450 1600 10 10 10 10 100 100 900 550 500 350
V V V A A A A A A A A A A
RDIS
5VOUT Discharge Impedance 3VOUT Discharge Impedance 12VOUT Discharge Impedance VEEOUT Discharge Impedance TIMER Pin Current TIMER Threshold Voltage (V12VIN - VTIMER) Circuit Breaker Trip Voltage (VAUXIN - VAUXSENSE) AUXGATE Gate Output Current
ITIMER VTIMER VAUXCB IAUXGATE VAUXGATE
q
-15
-22 45 0.9 50 -10 200 50 8
-27
A mA V mV A A mA V
q q
0.5 40 -6
1.3 60 -14
AUXON High, FAULT High, VAUXGATE = GND AUXON Low, FAULT High, VAUXGATE = 5V AUXON High, FAULT Low, VAUXGATE = 10V (VAUXGATE - VAUXIN), VAUXIN = 3.3V
q
External AUXGATE Gate Voltage
q
5
11
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.
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LTC4241 TYPICAL PERFOR A CE CHARACTERISTICS
3.3V and 5V Current Foldback Profile
12 10 3VOUT 5VOUT
OUTPUT CURRENT (mA)
OUTPUT CURRENT (A)
800 700 600 500 400 300 200 100 0
OUTPUT CURRENT (mA)
8 6 4 2 0 3VIN = 3.3V 5VIN = 5V RSENSE = 0.005 0.5 1.5 2.5 3.5 4.5 OUTPUT VOLTAGE (V) 5.5
4241 * G01
5VIN Current Limit Voltage vs Temperature
70
CURRENT LIMIT VOLTAGE (mV) 70
CURRENT LIMIT VOLTAGE (mV)
60 50 40 30 20 10 0 -75 -50 -25
5VOUT = 5V
CURRENT LIMIT (mA)
5VOUT = 0V
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G04
VEEIN Current Limit vs Temperature
600 55
CIRCUIT BREAKER TRIP VOLTAGE (mV)
GATE OUTPUT SOURCE CURRENT (A)
500
VEEOUT = -11V
CURRENT LIMIT (mA)
400 300 200 VEEOUT = 0V 100 0 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G07
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12V Current Foldback Profile
1100 1000 900 12VIN = 12V 1100 1000 900 800 700 600 500 400 300 200 100 0 1 2 3 4 5 6 7 8 9 10 11 12 OUTPUT VOLTAGE (V)
4241 * G02
-12V Current Foldback Profile
VEEIN = -12V
0
0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 OUTPUT VOLTAGE (V)
4241 * G03
3VIN Current Limit Voltage vs Temperature
1200 3VOUT = 3.3V 1000 800 600 400 200 60 50 40 30 20 10 0 -75 -50 -25 3VOUT = 0V
12VIN Current Limit vs Temperature
12VOUT = 11V
12VOUT = 0V
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G05
0 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G06
(VAUXIN - VAUXSENSE) Circuit Breaker Trip Voltage vs Temperature
90 80 70
54 53 52 51 50 49 48 47 46 45 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G08
GATE, AUXGATE Output Source Current vs Temperature
12.5
AUXGATE OUTPUT SOURCE CURRENT (A)
12.0 11.5 GATE 11.0 10.5 AUXGATE 10.0 9.5 9.0 8.5 0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G09
60 50 40 30 20 10 -75 -50 -25
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LTC4241 TYPICAL PERFOR A CE CHARACTERISTICS
GATE, AUXGATE Output Sink Current vs Temperature
350 300 GATE 250 200 150 100 50 -75 -50 -25 AUXGATE FAST PULL-DOWN CURRENT (mA) 80 70
OUTPUT SINK CURRENT (A)
(VAUXGATE - VAUXIN) (V)
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G10
AUXGATE Voltage vs Temperature
11.75
INTERNAL SWITCH VOLTAGE DROP (mV)
11.60
300 275 250 225 200 175 150 125
INTERNAL SWITCH VOLTAGE DROP (mV)
AUXGATE VOLTAGE (V)
11.45 11.30 11.15 11.00 10.85 10.70 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G13
Power Good Threshold Voltage vs Temperature (12VOUT)
11.20
4.68
POWER GOOD THRESHOLD VOLTAGE (V)
POWER GOOD THRESHOLD VOLTAGE (V)
11.15 11.10 11.05 11.00 10.95 10.90 -75 -50 -25
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 * G17
POWER GOOD THRESHOLD VOLTAGE (V)
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G16
UW
GATE, AUXGATE Fast Pull-Down Current vs Temperature
8.20 8.15 8.10 8.05 8.00 7.95 7.90 7.85 7.80
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G11
(VAUXGATE - VAUXIN) vs Temperature
AUXIN = 3.3V
60 50 40 GATE 30 20 10 0 -75 -50 -25 AUXGATE
7.75 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G12
12V Internal Switch Voltage Drop vs Temperature
325 I12VOUT = 500mA
200 180 160 140 120 100 80 60
VEE Internal Switch Voltage Drop vs Temperature
IVEEIN = 100mA
100 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G14
40 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G15
Power Good Threshold Voltage vs Temperature (5VOUT)
2.915 2.910 2.905 2.900 2.895 2.890 2.885 2.880
Power Good Threshold Voltage vs Temperature (3VOUT)
2.875 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G18
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LTC4241 TYPICAL PERFOR A CE CHARACTERISTICS
Power Good Threshold Voltage vs Temperature (VEEOUT)
-10.60 0.950 V12VIN - VTIMER -10.55 -10.50 -10.45 -10.40 -10.35 -10.30 -75 -50 -25
POWER GOOD THRESHOLD VOLTAGE (V)
TIMER THRESHOLD VOLTAGE (V)
TIMER CURRENT (A)
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G19
12VIN Supply Current vs Temperature
2.9 2.8
650 600 5VIN AUXIN
SUPPLY CURRENT (A)
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
SUPPLY CURRENT (mA)
2.7 2.6 2.5 2.4 2.3 2.2 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G22
5VIN Undervoltage Lockout Threshold vs Temperature
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
3.950 3.925 3.900 3.875 3.850 3.825 3.800 -75 -50 -25
(V5VIN - V5VSENSE) CIRCUIT BREAKER TRIP FILTER TIME (s)
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G25
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UW
Timer Threshold Voltage vs Temperature
23.00 22.75 22.50 22.25 22.00 21.75 21.50 21.25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G20
Timer Current vs Temperature
0.925 0.900 0.875 0.850 0.825 0.800 0.775 0.750 -75 -50 -25
21.00 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G21
VEEIN, 5VIN, 3VIN, AUXIN Supply Current vs Temperature
700 9.20 9.15 9.10 9.05 9.00 8.95 8.90 8.85
12VIN Undervoltage Lockout Threshold vs Temperature
550 500 450 400 350 300 250 200 -75 -50 -25 3VIN
VEEIN
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G23
8.80 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G24
3VIN, AUXIN Undervoltage Lockout Threshold vs Temperature
2.650 2.625 AUXIN 2.600 2.575 2.550 2.525 2.500 2.475 2.450 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G26
(V5VIN - V5VSENSE), (VAUXIN - VAUXSENSE) Circuit Breaker Trip Filter Time vs Temperature
18.50 18.25 18.00 VAUXIN - VAUXSENSE 17.75 17.50 17.25 17.00 16.75 16.50 -75 -50 -25 V5VIN - V5VSENSE 8.0 7.9 7.8 7.7 7.6 7.5 0 25 50 75 100 125 150 TEMPERATURE (C)
4241 * G27
8.3 8.2 8.1
(VAUXIN - VAUXSENSE) CIRCUIT BREAKER TRIP FILTER TIME (s)
3VIN
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PI FU CTIO S
12VIN (Pin 1): 12V Supply Input. This pin powers the primary controller internal circuitry. A 0.5 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 1.2 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 22A 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 15s 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 10A 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
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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 60A 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 200A 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 1.2 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 0.5 switch is connected between 12VIN and 12VOUT. 12VOUT must exceed 11.1V before the PWRGD signal can go low on the LTC4241
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GATE 15 5VOUT 12VIN 60A A1 A2 200A 3VSENSE 14 3VIN 13 3VOUT 3VOUT 5VOUT 3 18
5VIN 17
5VSENSE 16
+ - +
55mV
+ - +
55mV
Q8
+-
ON PWRGD 5 3.9V UVL
-
Q5
-
-+
2.5V UVL CP1
Q7
+
7 Q3 PRIMARY CONTROL LOGIC FAULT 6 Q4 CP2
-
REF
+ -
9V UVL Q9 Q1 22A 12VIN Q2 REF Q10 REF
+ -
REF 1 12VIN 20 12VOUT
CP4 Q6
+ -
4 TIMER 2 VEEIN 19 VEEOUT
CP3
PCI-BUS HOT SWAP CONTROLLER 8 GND
Q12 CHARGE PUMP 50mV
AUXIN 11
+ -
+
A3 8s FILTER
AUXILIARY CONTROL LOGIC
10A
AUXSENSE 10
-
2.6V UVL
Q11 Z1 12V 200A AUXIN 3.3V AUXILIARY SUPPLY HOT SWAP CONTROLLER Z2 20V
9 AUXGATE
AUXON 12
4241 BD
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LTC4241
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 1. Allows safe board insertion and removal from a motherboard. 2. Primary controller to control the four PCI supplies: 3.3V, 5V, -12V, 12V and an independent auxiliary controller to control the 3.3V auxiliary supply. 3. Adjustable foldback current limit for PCI supplies: an adjustable analog current limit with a value that depends on the output voltage. If the output is shorted to ground, the current limit drops to keep power dissipation and supply glitches to a minimum. 4. Electronic circuit breaker for all supplies: if a supply remains in current limit for too long, the circuit breaker will trip, the supplies will be turned off and the FAULT pin pulled low. 5. Current limit power-up: the four PCI supplies are allowed to power up in current limit. This allows the chip to power up boards with a wide range of capacitive loads without tripping the circuit breaker. The maximum allowable power-up time is programmable using the TIMER pin. 6. On-Chip -12V and 12V power switches 7. Power good output: monitors the voltage status of the four PCI supply voltages. The 3.3V auxiliary supply is not monitored.
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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
SUPPLY 5V 3.3V 12V -12V 3.3VAUX TOLERANCE 5V 5% 3.3V 0.3V 12V 5% -12V 10% 3.3V 0.3V CAPACITIVE LOAD <3000F <3000F <500F <120F <500F
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Power-Up Sequence for PCI Power Supplies The PCI power supplies are controlled by placing external N-channel pass transistors in the 3.3V and 5V power paths, and internal pass transistors for the 12V and -12V power paths (Figure 1). Resistors R1 and R2 provide a current signal for fault detection and R7 and C1 provide current control loop compensation. Resistors R4 and R5 prevent high frequency oscillations in Q1 and Q2. When the ON pin is pulled high, the GATE pin is pulled high by an internal 60A current source and the pass transistors are allowed to turn on. The internal 12V and -12V switches are also turned on and a 22A current source is connected to the TIMER pin (Figure 2).
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APPLICATIO S I FOR ATIO
ON 10V/DIV
TIMER 10V/DIV
GATE 10V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV
VEEOUT 5V/DIV FAULT 10V/DIV PWRGD 10V/DIV 10ms/DIV
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Figure 2. Normal Power-Up Sequence
The current in each pass transistor increases until it reaches the current limit for each supply. Each supply is allowed to power up at the rate dV/dt = 60A/C1 or as determined by the current limit and the load capacitance on the supply line, whichever is slower. Current limit faults are ignored while the TIMER pin voltage is ramping up and is less than 0.9V below 12VIN. Once all four PCI supply voltages are within tolerance, the PWRGD pin will pull low. Power-Down Sequence for PCI Power Supplies When the ON pin is pulled low, a power-down sequence begins for all the PCI power supplies (Figure 3). Internal switches are connected to each of the output supply voltage pins to discharge the load capacitors to ground. The TIMER pin is immediately pulled low and the internal 12V and -12V switches are turned off. The GATE pin is pulled to ground by an internal 200A current source. This turns off the external pass transistors in a controlled manner and prevents the load current on the 3.3V and 5V supplies from going to zero instantaneously and glitching the power supply voltages. When any of the output voltages dips below its threshold, the PWRGD pin pulls high.
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ON 10V/DIV TIMER 10V/DIV GATE 10V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV VEEOUT 5V/DIV FAULT 10V/DIV PWRGD 10V/DIV 10ms/DIV
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Figure 3. Normal Power-Down Sequence
Timer During a power-up sequence for the PCI power supplies, a 22A current source is connected to the TIMER pin and current limit faults are ignored until the voltage ramps to within 0.9V of 12VIN. This feature allows the chip to power up a PCI slot that can accommodate boards with a wide range of capacitive loads on the supplies. The power-up time for any one of the four outputs will be:
C *V tON 2 * LOAD OUT ILIMIT - ILOAD
For example, for CLOAD = 2000F, VOUT = 5V, ILIMIT = 7A, ILOAD = 5A, the 5VOUT turn-on time will be ~10ms. By substituting the variables in the above equation with the appropriate values, the turn-on time for the other three outputs can be calculated. The timer period should be set longer than the maximum supply turn-on time but short enough to not exceed the maximum safe operating area of the pass transistor during a short-circuit. The timer period is given by:
tTIMER =
C TIMER * 11.1V 22A
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LTC4241
APPLICATIO S I FOR ATIO
For CTIMER = 0.1F, the timer period will be ~50ms. The TIMER pin is immediately pulled low when ON goes low. Thermal Shutdown The internal switches for the 12V and -12V supplies are protected by an internal current limit and thermal shutdown circuit. When the temperature of the chip reaches 150C, only the switches controlling the PCI supplies will be latched off and the FAULT pin will be pulled low. Short-Circuit Protection for PCI Power Supplies During a normal power-up sequence for the PCI power supplies, if the TIMER is done ramping and any supply is still in current limit, all of the pass transistors will be immediately turned off, the TIMER and FAULT pin will be pulled low as shown in Figure 4.
ON 10V/DIV
TIMER 10V/DIV
GATE 10V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV VEEOUT 5V/DIV
FAULT 10V/DIV PWRGD 10V/DIV 20ms/DIV
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Figure 4. Power-Up into a Short on 3.3V Output
If a short-circuit occurs after the PCI supplies are powered up, the shorted supply's current will drop immediately to the limit value (Figure 5). If the supply remains in current limit for more than 17s, all of the PCI supplies except the 3.3V auxiliary supply will be latched off. The 17s delay prevents quick current
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spikes -- for example, from a fan turning on -- from causing false trips of the circuit breaker. The chip will stay in the latched-off state until the ON pin is cycled low then high, or the 12VIN supply is cycled. To prevent excessive power dissipation in the pass transistors and to prevent voltage spikes on the supplies during short-circuit conditions, the current limit on each PCI supply, except the 3.3V auxiliary supply, is designed to be a function of the output voltage. As the output voltage drops, the current limit decreases. Unlike a traditional circuit breaker function where huge currents can flow before the breaker trips, the current foldback feature assures that the supply current will be kept at a safe level and prevent voltage glitches when powering up into a short.
ON 10V/DIV TIMER 10V/DIV GATE 10V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV VEEOUT 5V/DIV FAULT 10V/DIV PWRGD 10V/DIV 20ms/DIV
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Figure 5. Short-Circuit on 5V Followed by Circuit Breaker Reset
The current limit and the foldback current level for the 5V and 3.3V outputs are both a function of the external sense resistor (R1 for 5VOUT and R2 for 3VOUT, see Figure 1). As shown in Figure 1, a sense resistor is connected between 5VIN and 5VSENSE for the 5V supply. For the 3V supply, a sense resistor is connected between 3VIN and 3VSENSE.
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APPLICATIO S I FOR ATIO
ILIMIT = 55mV/RSENSE IFOLDBACK = 9mV/RSENSE
The current limit and the foldback current level (at the VOUT = 0V) are given by:
As a design aid, the current limit and foldback level for commonly used values for RSENSE are given in Table 2.
Table 2. ILIMIT and IFOLDBACK vs RSENSE
RSENSE () 0.005 0.006 0.007 0.008 0.009 0.01 ILIMIT 11A 9.2A 7.9A 6.9A 6.1A 5.5A IFOLDBACK 1.8A 1.5A 1.3A 1.1A 1.0A 0.9A
The current limit for the internal 12V switch is set at 850mA folding back to 300mA and the -12V switch at 450mA folding back to 200mA. In systems where it is possible to exceed the current limit for a short amount of time, it might be necessary to prevent the analog current loop from responding quickly so the output voltage does not droop. This can be accomplished by adding an RC filter across the sense resistor as shown in Figure 6. RF should be 20 or less to prevent offset errors. A capacitor, CF, of 0.1F gives a delay of about 1.5s and a 1F capacitor gives a delay of about 15s.
5VIN R1 1 0.007 2 3 CF 1F 4 RF 20 R4 10 R7 100 C1 0.047F Q1 IRF7413 5VOUT 5A
17 * ADDITIONAL PINS OMITTED FOR CLARITY 5VIN
16 5VSENSE
15 18 GATE 5VOUT
LTC4241*
3.3VAUX 2V/DIV
Figure 6. Delay in the Current Limit Loop
Power-Up/Down Sequence for 3.3V Auxiliary Supply The 3.3V auxiliary supply is controlled by placing an external N-channel pass transistor Q3 in the 3.3VAUX
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power path (Figure 1). The resistor R3 provides load current fault detection and R6 prevents high frequency oscillation in Q3. When power is first applied to VAUXIN, the AUXGATE pin pulls low. A low-to-high transition at the AUXON pin initiates the AUXGATE ramp up (Figure 7). The AUXGATE is pulled high by an internal 10A current source and the pass transistor is allowed to turn on. As the auxiliary controller does not have the foldback current limit feature and timer control, the inrush supply current during powerup is limited by ramping the gate of the pass transistor at a controlled rate (dV/dt = 10A/C3) where C3 is the total external capacitance between AUXGATE and ground. With proper selection of the C3 capacitance value, the inrush current (I = CLOAD * dV/dt = 10A * CLOAD/C3) is limited to a value less than the current limit set by the sense resistor R3. This prevents the circuit breaker from tripping during power-up. CLOAD is the total load capacitance on the 3.3V auxiliary supply line. For example, for C3 = 10nF, CLOAD = 470F, R3 = 0.07, ILIMIT = 0.7A, the inrush current will be 0.47A < ILIMIT. The ramp-up time for 3.3VAUX output to reach its final value is equal to t = (VAUXIN * C3)/10A. A high-to-low transition at the AUXON pin initiates a AUXGATE ramp-down at a slope of -200A/C3 as the AUXGATE is pulled to ground by an internal 200A current source. This will allow the load capacitance on the supply line to discharge while the AUXGATE pulls low to turn off the external N-channel pass transistor.
AUXON 2V/DIV AUXGATE 5V/DIV 5ms/DIV
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Figure 7. Power-Up/Down Sequence for 3.3V Auxiliary Supply
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LTC4241
APPLICATIO S I FOR ATIO
Electronic Circuit Breaker for 3.3V Auxiliary Supply An electronic circuit breaker is used to protect against excessive load current and short-circuits on the 3.3V auxiliary supply. The load current is monitored by placing a sense resistor R3 between AUXIN and AUXSENSE as shown in Figure 1. The circuit breaker trip threshold is 50mV and exhibits a response time of 8s. Unlike the PCI supplies which use the current foldback limit with circuit breaker during short-circuits, here the circuit breaker will trip and immediately pull AUXGATE to ground if the voltage between AUXIN and AUXSENSE exceeds 50mV for more than 8s. The external N-channel transistor is turned off and FAULT is pulled low. The circuit breaker is reset when AUXON is cycled low then high, or the AUXIN supply is cycled. If the circuit breaker feature is not required, the AUXSENSE pin can be shorted to AUXIN. The trip current of the circuit breaker is set by: ITRIP = 50mV/R3 As a design aid, the trip current for commonly used values for R3 is given in Table 3.
Table 3. ITRIP vs R3
R3 () 0.05 0.06 0.07 0.08 0.09 0.1 ITRIP 1A 833mA 714mA 625mA 556mA 500mA
If more than 8s of response time is needed to reject supply current ripple noise, an external resistor, RF, of 20 and capacitor, CF, of 1F (Figure 6) can be added to the AUXSENSE circuit. This will give a delay of 15s.
Table 4. N-Channel Power MOSFET Selection Guide
CURRENT RATING 8.0A 3.5A 10A 13A 2.7A PART NUMBER Si4412ADY Si2306DS Si4410DY IRF7413 FDN 359AN PACKAGE SO-8 SOT-23 SO-8 SO-8 SOT-23
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Supply Bypass Capacitors In motherboard applications, large bypass capacitors are recommended at each of the system power supplies to minimize supply glitches as a result of board insertion. A supply bypass capacitor of 100F at 12VIN connection is recommended.
CURRENT FLOW FROM SUPPLY CURRENT FLOW TO LOAD SENSE RESISTOR TRACK WIDTH W: 0.03" PER AMPERE ON 1 OZ COPPER FOIL W
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5VIN
5VSENSE
Figure 8. Making PCB Connections to the Sense Resistor for the 5V Rail
PCB Layout Considerations for the Sense Resistor For proper circuit breaker operation, 4-wire Kelvin-sense connections between the sense resistor and the LTC4241's 5VIN and 5VSENSE pins, 3VIN and 3VSENSE pins and AUXIN and AUXSENSE pins are strongly recommended. The drawing in Figure 8 illustrates the correct way of making connections between the LTC4241 and the sense resistor. PCB layout should be balanced and symmetrical to minimize wiring errors. In addition, the PCB layout for the sense resistors and the power MOSFETs should include good thermal management techniques for optimal sense resistor power dissipation. Power MOSFET and Sense Resistor Selection Table 4 lists some available N-channel power MOSFETs . Table 5 lists some current sense resistors that can be used with the LTC4241's circuit breakers. Table 6 lists the supplier web site addresses for discrete components mentioned throughout this datasheet.
VGSMAX 20V 20V 20V 20V 20V RDS(on) 0.024 0.057 0.013 0.011 0.046 MANUFACTURER Vishay-Siliconix Vishay-Siliconix Vishay-Siliconix International Rectifier Fairchild Semiconductor
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VDS MAX 30V 30V 30V 30V 30V
LTC4241
APPLICATIO S I FOR ATIO
Table 5. Sense Resistor Selection Guide
CURRENT LIMIT VALUE 0.7A 1A 2A 5A 7.9A 11A PART NUMBER WSL2010R07 LR120601R055F WSL2010R055 LR120601R028F WSL2010R028 LR120601R011F WSL2010R011 WSL2512R007 WSL2512R005 DESCRIPTION 0.07, 0.5W, 1% Resistor 0.055, 0.5W, 1% Resistor 0.028, 0.5W, 1% Resistor 0.011, 0.5W, 1% Resistor 0.007, 1W, 1% Resistor 0.005, 1W, 1% Resistor MANUFACTURER Vishay-Dale IRC-TT Vishay-Dale IRC-TT Vishay-Dale IRC-TT Vishay-Dale Vishay-Dale Vishay-Dale
Table 6. Manufacturers' Web Site
MANUFACTURER International Rectifier Fairchild Semiconductor IRC-TT Vishay-Dale Vishay-Siliconix Diodes, Inc. WEB SITE www.irf.com www.fairchildsemi.com www.irctt.com www.vishay.com www.vishay.com www.diodes.com
PACKAGE DESCRIPTIO
GN Package 20-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
.045 .005 .337 - .344* (8.560 - 8.737) 20 19 18 17 16 15 14 13 12 11 .058 (1.473) REF
.254 MIN
.150 - .165
.0165 .0015 RECOMMENDED SOLDER PAD LAYOUT
.0250 TYP 1 .053 - .068 (1.351 - 1.727) 23 4 56 7 8 9 10 .004 - .0098 (0.102 - 0.249) .015 .004 x 45 (0.38 0.10)
.007 - .0098 (0.178 - 0.249) .016 - .050 (0.406 - 1.270)
0 - 8 TYP
NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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.229 - .244 (5.817 - 6.198) .150 - .157** (3.810 - 3.988) .008 - .012 (0.203 - 0.305) .0250 (0.635) BSC
GN20 (SSOP) 0502
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LTC4241
TYPICAL APPLICATIO
SYSTEM POWER SUPPLY
3
8 1 2 12 5 PCI POWER SYSTEM CONTROLLER R8 10k 6 R9 10k 7
AUXIN AUXSENSE GND 12VIN VEEIN AUXON ON FAULT PWRGD
RELATED PARTS
PART NUMBER LTC1421 LTC1422 LT1641-1/LT1641-2 LTC1642 LTC1643AL/LTC1643AL-1/LTC1643AH LTC1644 LTC1645 LTC1646 LTC1647-1/LTC1647-2/LTC1647-3 LTC4211 LTC4230 LT4250L/LT4250H LTC4251 LTC4252 LTC4253 LTC4350 DESCRIPTION 2-Channel Hot Swap Controller Hot Swap Controller in SO-8 High Voltage Hot Swap Controller Fault Protected Hot Swap Controller PCI-Bus Hot Swap Controller CompactPCI Bus Hot Swap Controller 2-Channel Hot Swap Controller CompactPCI Dual Hot Swap Controller Dual Hot Swap Controllers Single Channel, Hot Swap Controller Triple Channel, Hot Swap Controller - 48V Hot Swap Controller in S0-8 -48V Hot Swap Controller in S0T-23 -48V Hot Swap Controller in MSOP -48V Hot Swap Controller and Sequencer Hot Swappable Load Share Controller COMMENTS Operates from 3V to 12V and Supports -12V System Reset Output with Programmable Delay Operates from 9V to 80V, SO-8 Package, Latch Off/Auto Retry Operates Up to 16.5V, Protected to 33V 3.3V, 5V and 12V in Narrow 16-Pin SSOP Package 3.3V, 5V and 12V, 1V Precharge, Local PCI Logic Operates from 1.2V to 12V, Power Sequencing 3.3V and/or 5V Supplies, 1V Precharge, Local PCI Reset Logic Operates from 2.7V to 16.5V 2.5V to 16.5V Operation, Multilevel Current Control, MSOP Package 1.7V to 16.5V Operation, Multilevel Current Control Operates from -20V to -80V, Active Current Limiting -48V Hot Swap Controller, Active Current Limiting Active Current Limiting With Drain Acceleration Active Current Limiting With Drain Acceleration and Three Sequenced Power Good Outputs Output Voltages from 1.5V to 12V
CompactPCI is a trademark of the PCI Industrial Computer Manufactures Group ThinSOT is a trademark of Linear Technology Corporation
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
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GND R1 1 0.007 2 3 R3 1 0.07 2 4 C3 10nF R6 10 9 13 17 14 16 15 3 18 R7 100 C1 0.047F Q3 Si4412ADY 4 R4 10 3.3VAUX 500mA Q1 IRF7413 5V 5A 11 10 AUXGATE 3VIN 5VIN 3VSENSE 5VSENSE GATE 3VOUT 5VOUT 12V 500mA -12V 100mA BACKPLANE CONNECTOR C2 0.1F
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12VOUT LTC4241 VEEOUT TIMER
20 19 4
Figure 9. System Without 3.3V Supply
LT/TP 0303 2K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2002

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