LTC4241IGN

LTC4241 PCI-Bus with 3.3V Auxiliary Hot Swap Controller FEATURES s s DESCRIPTIO s s s s s s 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 s s PCI-Based Servers Computer Systems 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. 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 0.007Ω Q1 IRF7413 R2 0.005Ω Q2 IRF7413 SYSTEM POWER SUPPLY R3 0.07Ω Q3 Si2306DS R5 10Ω C3 10nF R6 10Ω 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 0.1µF LOGIC RESET 4241 F01 12VOUT LTC4241 VEEOUT TIMER Figure 1. Hot Swappable PCI and 3.3V Auxiliary Supplies sn4241 4241f U GND 5V 5A R4 10Ω 3.3V 7.6A 3.3VAUX 500mA R7 100Ω C1 0.047µF 20 19 4 U U 1 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 ........................................... 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 LTC4241CGN LTC4241IGN AUXSENSE 10 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 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 = 25°C. 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 sn4241 4241f 2 U mV mV mV mV µs µs µA µA mA W U U WW W 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 = 25°C. 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 µA µA µA µA µA µA µA µA µA µA Ω Ω Ω Ω 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 µA mA V mV µA µA 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. sn4241 4241f 3 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 = 0.005Ω 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 (µA) 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 4 UW 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 (µA) 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 sn4241 4241f 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 (µA) (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 sn4241 4241f 5 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 (µA) 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 (µA) 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 (µs) 0 25 50 75 100 125 150 TEMPERATURE (°C) 4241 • G25 6 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 (µs) 3VIN sn4241 4241f LTC4241 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 U U U 7 LTC4241 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 8 U U U sn4241 4241f LTC4241 BLOCK DIAGRA W GATE 15 5VOUT 12VIN 60µA A1 A2 200µA 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 12VIN Q2 22µA 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 8µs FILTER AUXILIARY CONTROL LOGIC 10µA AUXSENSE 10 – 2.6V UVL Q11 Z1 12V 200µA AUXIN 3.3V AUXILIARY SUPPLY HOT SWAP CONTROLLER Z2 20V 9 AUXGATE AUXON 12 4241 BD sn4241 4241f 9 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. 10 U 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