LTC1643L/LTC1643L-1/LTC1643H PCI-Bus Hot Swap Controller U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Allows Safe Board Insertion and Removal from a Live PCI Slot Works on either a Motherboard (LTC1643H) or CompactPCITM Card (LTC1643L/LTC1643L-1) Controls –12V, 3.3V, 5V, 12V Supplies Programmable Foldback Current Limit with Circuit Breaker User-Programmable Supply Voltage Power-Up Rate High Side Drive for External N-Channels –12V and 12V On-Chip Switches Fault and Power-Good Outputs The LTC®1643 is a Hot SwapTM controller that allows a board to be safely inserted and removed from a live PCI-Bus slot. Two external N-channel transistors control the 3.3V and 5V supplies while on-chip switches control the –12V and 12V supplies. All supply voltages can be ramped up at a programmable rate. An electronic circuit breaker protects all four supplies against overcurrent faults. The foldback current limit feature limits current spikes and power dissipation when shorts occur and allows boards with large capacitances to be powered up without tripping the circuit breaker. The PWRGD output indicates when all of the supply voltages are within tolerance and the FAULT output indicates an overcurrent condition. The ON(LTC1643H)/ON (LTC1643L/LTC1643L-1) pin is used to cycle the board power or reset the circuit breaker. The LTC1643L-1 has the ±12V power good comparators disabled. The LTC1643 is available in a 16-pin narrow SSOP package. U APPLICATIO S ■ ■ PCI-Based Servers CompactPCI Compliant Boards , LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. CompactPCI is a trademark of PCI Industrial Computer Manufacturing Group. U TYPICAL APPLICATION Hot Swappable PCI Supply R1 0.007Ω R2 0.005Ω 3.3V 7.6A GND R5 10Ω 9 3VIN GND 1 12VIN 2 VEEIN 5 ON 8 RESET 5V 5A R6 10Ω Q2 IRF7413 SYSTEM POWER SUPPLY PCI POWER SYSTEM CONTROLLER Q1 IRF7413 R3 10k R4 10k 6 10 11 3VSENSE GATE R7 100Ω 3 13 3VOUT 5VIN 12 5VSENSE 5VOUT 12VOUT LTC1643H VEEOUT FAULT TIMER 7 PWRGD C1 0.047µF 14 16 12V 500mA 15 –12V 100mA 4 C2 0.1µF LOGIC RESET 1643 TA01 1 LTC1643L/LTC1643L-1/LTC1643H W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Supply Voltages 12VIN ................................................................ 13.2V VEEIN .............................................................. –13.2V Input Voltage (Pin 5) ................ – 0.3V to (12VIN + 0.3V) Output Voltages (Pins 6, 7) ...... – 0.3V to (12VIN + 0.3V) Analog Voltages (Pins 3, 4, 9, 10 to 14) ........ – 0.3V to (12VIN + 0.3V) VEEOUT ............................................ –13.2V to + 0.3V 12VOUT .............................................. – 0.3V to 13.2V Operating Temperature Range Commercial ............................................. 0°C to 70°C Industrial ........................................... – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW 12VIN 1 16 12VOUT VEEIN 2 15 VEEOUT 3VOUT 3 14 5VOUT TIMER 4 13 5VIN ON/ON* 5 FAULT 6 PWRGD 7 12 5VSENSE 11 GATE 10 3VSENSE GND 8 9 LTC1643HCGN LTC1643LCGN LTC1643L-1CGN LTC1643HIGN LTC1643LIGN 3VIN GN PACKAGE 16-LEAD NARROW PLASTIC SSOP * ON FOR LTC1643H, ON FOR LTC1643L TJMAX = 150°C, θJA = 135°C/ W Consult factory for Military grade parts. DC ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. V12VIN = 12V, VEE = – 12V, V3VIN = 3.3V, V5VIN = 5V. (Note 2) SYMBOL PARAMETER CONDITIONS IDD V12VIN Supply Current ON = 3V, ON = GND ● VLKO Undervoltage Lockout 12VIN 3VIN 5VIN ● VFB = (V5VIN – V5VSENSE), V5VOUT = 0V VFB = (V5VIN – V5VSENSE), V5VOUT > 4V VFB = (V3VIN – V3VSENSE), V3VOUT = 0V VFB = (V3VIN – V3VSENSE), V3VOUT > 2V ● Charge Pump On, VGATE = GND, FAULT = High Charge Pump Off, VGATE = 5V, FAULT = High Charge Pump Off, VGATE = 2V, FAULT = Low VFB Foldback Current Limit Voltage tCB Circuit Breaker Trip Filter Time ICP GATE Pin Output Current MIN TYP MAX 3.5 8 7 2.25 2.25 9.5 2.5 2.5 10.8 2.75 2.75 ● 4 40 4 40 7.5 53 7.5 53 12 65 12 65 mV mV mV mV ● – 20 – 100 ● 3 – 50 200 10 20 µA µA mA 100 200 mV 250 250 600 750 mV mV 120 250 mV 250 850 160 450 500 1500 215 800 mA mA mA mA ● ● ● ● External Gate Voltage (V12VIN – VGATE) VDROP Internal Switch Voltage Drop (V12VIN – V12VOUT), I12VOUT = 500mA C Grade I Grade ● (VEEOUT – VEEIN), IVEEIN = 100mA ● 12VIN = 12V, 12VOUT = 0V 12VIN, 12VOUT = 12V VEEIN = –12V, VEEOUT = 0V VEEIN, VEEOUT = – 12V ● ICL Current Foldback TTS Thermal Shutdown Temperature VTH Power-Good Threshold Voltage 2 ● ● ● ● 50 525 100 225 C Grade I Grade ● VEEOUT LTC1643H/LTC1643L Only C Grade I Grade ● ● ● V V V °C 150 V12VOUT LTC1643H/LTC1643L Only mA µs 14.6 ∆VGATE UNITS 10.8 10.4 11.1 11.1 11.4 11.4 V V – 10.2 – 10.0 – 10.5 – 10.5 – 10.8 – 10.8 V V LTC1643L/LTC1643L-1/LTC1643H DC ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. V12VIN = 12V, VEE = – 12V, V3VIN = 3.3V, V5VIN = 5V.(Note 2) SYMBOL VTH PARAMETER CONDITIONS Power-Good Threshold Voltage MIN V3VOUT V5VOUT C Grade I Grade ● C Grade I Grade ● ● ● VIL Input Low Voltage ON/ON, FAULT ● VIH Input High Voltage ON/ON, FAULT ● VOL Output Low Voltage FAULT, PWRGD, I = 3mA ● IIN ON/ON Pin Input Current ON/ON = GND ON/ON= 12VIN ● 5VSENSE Input Current TYP MAX UNITS 2.8 2.75 2.9 2.9 3.0 3.0 V V 4.5 4.4 4.65 4.65 4.75 4.75 V V 0.8 V 2 V 0.4 V ● ± 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 ● 460 700 µA 3VIN Input Current 3VIN = 3V ● 320 600 µA 5VOUT Input Current 5VOUT = 5V, ON = 3V, ON = GND ● 240 500 µA 3VOUT Input Current 3VOUT = 3.3V, ON = 3V, ON = GND ● 220 500 µA RDIS 5VOUT Discharge Impedance 3VOUT Discharge Impedance 12VOUT Discharge Impedance VEEOUT Discharge Impedance ON = GND or ON = 3V ON = GND or ON = 3V ON = GND or ON = 3V ON = GND or ON = 3V ITIMER TIMER Pin Current Timer On, VTIMER = GND Timer Off, VTIMER = 5V ● – 15 – 22 45 – 27 µA mA VTIMER TIMER Threshold Voltage (V12VIN – VTIMER) ● 0.5 0.9 1.3 V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Ω Ω Ω Ω 100 70 450 1600 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. U W TYPICAL PERFORMANCE CHARACTERISTICS 3.3V and 5V Current Foldback Profile 12V Current Foldback Profile – 12V Current Foldback Profile 11 1.0 3VOUT 8 7 OUTPUT CURRENT (A) OUTPUT CURRENT (A) 9 5VOUT 6 5 4 3 1.0 OUTPUT CURRENT (A) 10 0.5 0.5 2 1 0 RSENSE = 0.005Ω 0 1 3 4 2 OUTPUT VOLTAGE (V) 5 1643 G01 0 0 2 6 8 4 OUTPUT VOLTAGE (V) 10 12 1643 G02 0 0 –2 –6 –8 –10 –4 OUTPUT VOLTAGE (V) –12 1643 G03 3 LTC1643L/LTC1643L-1/LTC1643H U W TYPICAL PERFORMANCE CHARACTERISTICS Timer Current vs Temperature FAULT = LOW 22.5 80 22.0 21.5 21.0 GATE CURRENT (µA) 22.5 GATE ISINK (mA) 20.0 17.5 15.0 20.5 19.5 –50 –25 0 25 50 75 100 10.0 –50 –25 125 TEMPERATURE (°C) 50 25 75 0 TEMPERATURE (°C) 1643 G04 11.00 10.98 –50 –25 50 0 75 25 TEMPERATURE (°C) 100 4.63 4.62 4.61 4.60 4.59 50 25 75 0 TEMPERATURE (°C) 125 2.902 2.901 2.900 2.899 2.898 2.897 2.896 –50 –25 INTERNAL SWITCH VOLTAGE DROP (mV) –10.44 –10.42 –10.40 –10.38 –10.36 0 25 50 75 100 125 TEMPERATURE (°C) 1643 G10 0 25 50 75 100 125 TEMPERATURE (°C) 1643 G09 VEE Internal Switch Voltage Drop vs Temperature 180 325 –10.46 –10.34 –50 –25 100 2.903 12V Internal Switch Voltage Drop vs Temperature –10.50 125 Power Good Threshold Voltage vs Temperature (3VOUT) 1643 G08 1643 G07 Power Good Threshold Voltage vs Temperature (VEEOUT) 100 2.904 4.58 –50 –25 125 –10.48 50 0 75 25 TEMPERATURE (°C) 1643 G06 POWER GOOD THRESHOLD VOLTAGE (V) POWER GOOD THRESHOLD VOLTAGE (V) POWER GOOD THRESHOLD VOLTAGE (V) 40 –50 –25 125 4.64 11.02 4 100 Power Good Threshold Voltage vs Temperature (5VOUT) 11.08 11.04 60 1643 G05 Power Good Threshold Voltage vs Temperature (12VOUT) 11.06 70 50 12.5 20.0 I12VOUT = 500mA INTERNAL SWITCH VOLTAGE DROP (mV) TIMER CURRENT (µA) 90 25.0 23.0 POWER GOOD THRESHOLD VOLTAGE (V) Gate Current vs Temperature Gate ISINK vs Temperature 23.5 300 275 250 225 200 175 150 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 LT1643 G11 IVEEIN = 100mA 160 140 120 100 80 60 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1643 G12 LTC1643L/LTC1643L-1/LTC1643H U W TYPICAL PERFORMANCE CHARACTERISTICS Timer Threshold Voltage vs Temperature Circuit Breaker Trip Filter Time vs Temperature 3.72 15.25 15.00 14.75 14.50 14.25 14.00 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 12VIN SUPPLY CURRENT (mA) 1.0 TIMER THRESHOLD VOLTAGE (V) CIRCUIT BREAKER TRIP FILTER TIME (µs) 15.50 0.9 0.8 0.7 –50 –25 125 3.66 3.64 50 25 75 0 TEMPERATURE (°C) 100 3.62 –50 –25 125 0.86 0.85 3VIN SUPPLY CURRENT (µA) 5VIN SUPPLY CURRENT (µA) 0.87 266 264 262 260 256 –50 –25 125 272.5 270.0 267.5 265.0 262.5 258 100 50 25 75 0 TEMPERATURE (°C) 100 260.0 –50 –25 125 50 25 75 0 TEMPERATURE (°C) LT1643 G17 1643 G16 350 100 125 1643 G18 12VIN Undervoltage Lockout vs Temperature VOL vs Temperature 125 275.0 268 0.88 100 3VIN Supply Current vs Temperature 270 0.89 50 0 75 25 TEMPERATURE (°C) 1643 G15 5VIN Supply Current vs Temperature 0.90 50 25 75 0 TEMPERATURE (°C) 3.68 1643 G14 VEEIN Supply Current vs Temperature 0.84 –50 –25 3.70 V12VIN – VTIMER 1643 G13 VEEIN SUPPLY CURRENT (mA) 12VIN Supply Current vs Temperature 5VIN Undervoltage Lockout vs Temperature 9.515 2.454 9.510 2.452 UNDERVOLTAGE LOCKOUT (V) 300 FAULT VOL (mV) 250 200 150 PWRGD 100 50 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1643 G19 UNDERVOLTAGE LOCKOUT (V) I = 3mA 9.505 9.500 9.495 9.490 9.485 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1643 G20 2.450 2.448 2.446 2.444 2.442 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1643 G21 5 LTC1643L/LTC1643L-1/LTC1643H U W TYPICAL PERFORMANCE CHARACTERISTICS 3VIN Undervoltage Lockout vs Temperature 2.454 70 2.452 2.450 2.448 2.446 2.444 2.442 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 70 60 5VOUT = 5V 50 40 30 20 5VOUT = 0V 10 0 –50 –25 125 FOLDBACK CURRENT LIMIT VOLTAGE (mV) FOLDBACK CURRENT LIMIT VOLTAGE (mV) UNDERVOLTAGE LOCKOUT (V) 3VIN Foldback Current Limit Voltage vs Temperature 5VIN Foldback Current Limit Voltage vs Temperature 50 25 75 0 TEMPERATURE (°C) 1643 G21 100 1200 500 1000 300 VEEOUT = 0V 100 75 100 3VOUT = 0V 10 50 25 75 0 TEMPERATURE (°C) 100 VOL vs ISINK (25°C) 700 FAULT 600 800 600 500 400 300 400 12VOUT = 0V 0 –50 125 800 PWRGD 200 200 50 25 0 TEMPERATURE (°C) 20 LT1643 G24 VOL (mV) CURRENT FOLDBACK (mA) CURRENT FOLDBACK (mA) 400 –25 30 0 –50 –25 125 12VOUT = 12V 0 –50 40 12V Current Foldback vs Temperature 600 200 50 LT1643 G23 VEE Current Foldback vs Temperature VEEOUT = –12V 3VOUT = 3.3V 60 100 0 –25 50 25 0 TEMPERATURE (°C) 1643 G25 75 100 1643 G26 0 2 4 6 ISINK (mA) 8 10 1643 G27 U U U PIN FUNCTIONS 12VIN (Pin 1): 12V Supply Input. It powers all the chip’s 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 9.5V typically. VEEIN (Pin 2): – 12V Supply Input. A 1.2Ω switch is connected between VEEIN and VEEOUT with a fold-back current limit. 3VOUT (Pin 3): Analog Input. Used to monitor the 3.3V output supply voltage. The PWRGD signal cannot go high until the 3VOUT pin exceeds 2.9V typically. 6 TIMER (Pin 4): Analog Current Fault Inhibit Timing Input. Connect a capacitor from TIMER to GND. With the chip turned off (ON = GND or ON = High) or the internal circuit breaker tripped (FAULT = GND), the TIMER pin is internally held at GND. When the chip is turned on, a 20µA pull-up current source is connected to TIMER. Current limit faults will be ignored until the voltage at the TIMER pin rises to within 0.9V of 12VIN. ON/ON (Pin 5): Digital Input.The LTC1643L/LTC1643L-1 have an active low enable, ON, and the LTC1643H has an active high enable, ON. When the ON pin is pulled high or LTC1643L/LTC1643L-1/LTC1643H U U U PIN FUNCTIONS the ON pin pulled low, the GATE pin is pulled high by a 50µA current source and the internal 12V and – 12V switches are turned on. When the ON pin is pulled low or the ON pin pulled high, the GATE pin will be pulled to ground by a 200µA current source and the 12V and – 12V switches turned off. The ON/ON pin is also used to reset the electronic circuit breaker. If the ON/ON pin is cycled following the trip of the circuit breaker, the circuit breaker is reset and a normal power-up sequence will occur. FAULT (Pin 6): Open-Drain Digital I/O. FAULT is pulled low when a current limit fault is detected. Current limit faults are ignored while the voltage at the TIMER pin is less than 12VIN – 0.9V. Once the TIMER cycle is complete, FAULT will pull low typically 14.6µs after any of the supplies go into current limit. At the same time the GATE and TIMER pins are pulled to GND and the 12V and –12V switches are turned off. The chip will remain latched in the off state until the ON/ON pin is toggled or the power is cycled. 3VSENSE (Pin 10): The 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 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 GND. To disable the current limit, 3VSENSE and 3VIN can be shorted together. GATE (Pin 11): High Side Gate Drive for the External N-Channels. 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 50µA current source connected to 12VIN and the external capacitor connected to GND or by the 3.3V or 5V current limit and the bulk capacitance on the 3VOUT or 5VOUT suppy lines. During power-down, the slope of the falling voltage is set by the 200µA current source connected to GND and the external GATE capacitor. Forcing the FAULT pin low with an external pull-down will immediately turn off the internal switches and force the GATE and TIMER pins to GND independent of the state of the ON/ON pin. However, the chip is not latched into the off state, so when the FAULT pin is released, the state of the chip will be determined by the ON pin. The voltage at the GATE pin will be modulated to maintain a constant current when either the 3V or 5V supplies go into current limit. When a current limit fault occurs after the inhibit period set by the TIMER pin capacitance, the undervoltage lockout circuit on 3.3V, 5V or 12V trips or the FAULT pin is pulled low, the GATE pin is immediately pulled to GND. PWRGD (Pin 7): Open-Drain Digital Power-Good Output. PWRGD remains low while V12VOUT ≥ 11.4V, V3VOUT ≥ 3V, V5VOUT ≥ 4.75V and VEEOUT ≤ – 10.8V. The LTC1643L-1 has the power good comparators connected to the 12VOUT and VEEOUT pins disabled, with only the 3VOUT and 5VOUT outputs being monitored to generate PWRGD. 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. 5VSENSE (Pin 12): 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 GND. To disable the current limit, 5VSENSE and 5VIN can be shorted together. GND (Pin 8): Chip Ground. 3VIN (Pin 9): 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 typically. If no 3.3V input supply is available, tie 3VIN to the 5VIN pin. 5VIN (Pin 13): Analog 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 2.5V typically. 5VOUT (Pin 14): Analog Input. Used to monitor the 5V output supply voltage. The PWRGD signal cannot go high until the 5VOUT pin exceeds 4.65V typically. 7 LTC1643L/LTC1643L-1/LTC1643H U U U PIN FUNCTIONS VEEOUT (Pin 15): –12V Supply Output. A 1.2Ω switch is connected between VEEIN and VEEOUT. VEEOUT must exceed –10.8V before the PWRGD signal can go high on the LTC1643H and LTC1643L. 12VOUT (Pin 16): 12V Supply Output. A 0.5Ω switch is connected between 12VIN and 12VOUT. 12VOUT must exceed 11.4V before the PWRGD signal can go high on the LTC1643H and LTC1643L. W BLOCK DIAGRAM 5VIN 5VSENSE 3VSENSE 3VIN GATE 11 12 10 12VIN – + 5VOUT 3VOUT 5VOUT 9 3 14 – + 3VOUT 50µA + + – Q8 – Q5 2.5V UVL 200µA Q7 2.5V UVL CP3 ON/ON 5 + 13 – Q3 CP4 LOGIC PWRGD 7 REF + FAULT 6 – Q4 12VIN 9.5V UVL Q1 REF REF Q9 Q2 20µA + CP5 + CP7 Q6 – Q10 – REF 1643 BD 12VIN 12VOUT LTC1643H/LTC1643L ONLY W 16 4 2 15 TIMER VEEIN VEEOUT LTC1643H/LTC1643L ONLY 8 GND U 1 U U APPLICATIONS INFORMATION 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 cause glitches on the power bus, causing other boards in the system to reset. The LTC1643 is designed to turn a board’s supply voltages on and off in a controlled manner, allowing the board to be 8 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 LTC1643H is designed for motherboard applications, while the LTC1643L/LTC1643L-1 are designed for CompactPCI applications where the chip resides on the plug-in board. LTC1643L/LTC1643L-1/LTC1643H U U W U APPLICATIONS INFORMATION LTC1643 FEATURE SUMMARY 1. Allows safe board insertion and removal from either a motherboard (LTC1643H) or CompactPCI board (LTC1643L/LTC1643L-1). Some ±12V supplies in CompactPCI applications are not well regulated and can violate the tolerance specification. For these applications, the LTC1643L-1 should be used because the PWRGD signal does not depend on ±12V outputs. 2. Controls all four PCI supplies: –12V, 12V, 3.3V and 5V. 3. Programmable foldback current limit: a programmable 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. Power-Up Sequence 4. Programmable circuit breaker: if a supply remains in current limit too long, the circuit breaker will trip, the supplies will be turned off and the FAULT pin pulled low. Resistors R1 and R2 provide current fault detection and R7 and C1 provide current control loop compensation. Resistors R5 and R6 prevent high frequency oscillations in Q1 and Q2. 5. Current limit power-up: the supplies are allowed to power up in current limit. Allows the chip to power up boards with widely varying capacitive loads without tripping the circuit breaker. The maximum allowable power-up time is programmable using the TIMER pin. 6. –12V and 12V power switches on chip. 7. Power good output: monitors the voltage status of the four supply voltages, except the LTC1643L-1 which only monitors 3VOUT and 5VOUT. 8. Space saving 16-pin 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. Systems implementing the 5V signaling environment may either ship the 3.3V supply with the system or provide a means to add it afterward. The tolerance of the supplies as measured at the components on the plug-in card is summarized in Table 1. Table 1. PCI Power Supply Requirements SUPPLY TOLERANCE CAPACITIVE LOAD 5V 5V ±5% < 3000µF 3.3V 3.3V ±0.3V < 3000µF 12V 12V ±5% < 500µF – 12V –12V ±10% < 120µF The 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). When the ON pin (Pin 5) is pulled high, the pass transistors are allowed to turn on and a 20µA current source is connected to the TIMER pin (Pin 4) (Figure 2). The current in each pass transistor increases until it reaches the current limit for each supply. Each supply is then allowed to power up at the rate dv/dt = 50µA/C1 or as determined by the current limit and the load capacitance whichever is slower. Current limit faults are ignored while the TIMER pin (Pin 4) voltage is ramping up and is less than 0.9V below 12VIN (Pin 1). Once all four supply voltages are within tolerance, the PWRGD pin (Pin 7) will pull low. Power-Down Sequence When the ON (Pin 5) is pulled low, a power-down sequence begins (Figure 3). Internal switches are connected to each of the output supply voltage pins to discharge the bypass capacitors to ground. The TIMER pin (Pin 4) is immediately pulled low. The GATE pin (Pin 11) is pulled down by a 200µA current source to prevent the load currents on the 3.3V and 5V supplies from going to zero instantaneously and glitching the power supply voltages. When any of the output voltages dip below its threshold, the PWRGD pin (Pin 7) pulls high. 9 LTC1643L/LTC1643L-1/LTC1643H U U W U APPLICATIONS INFORMATION R1 0.007Ω R2 0.005Ω 5V 5A R6 10Ω Q2 IRF7413 3.3V 7.6A GND SYSTEM POWER SUPPLY R5 10Ω 9 3VIN GND 1 12VIN 2 VEEIN 5 ON 8 PCI POWER SYSTEM CONTROLLER Q1 IRF7413 R3 10k R4 10k 6 10 R7 100Ω 11 3VSENSE GATE 3 13 3VOUT 5VIN 12 5VSENSE 5VOUT 12VOUT LTC1643H VEEOUT FAULT TIMER 7 PWRGD RESET C1 0.047µF 14 16 12V 500mA 15 –12V 100mA 4 C2 0.1µF LOGIC RESET 1643 F01 Figure 1. Typical Application ON 10V/DIV ON 10V/DIV TIMER 10V/DIV TIMER 10V/DIV GATE 10V/DIV GATE 10V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV VEEOUT 5V/DIV VEEOUT 5V/DIV FAULT 10V/DIV FAULT 10V/DIV PWRGD 10V/DIV PWRGD 10V/DIV 10ms/DIV Figure 2. Normal Power-Up Sequence 10 1643 F02 10ms/DIV Figure 3. Normal Power-Down Sequence 1643 F03 LTC1643L/LTC1643L-1/LTC1643H U W U U APPLICATIONS INFORMATION Timer During a power-up sequence, a 20µA current source is connected to the TIMER pin (Pin 4) and current limit faults are ignored until the voltage ramps to within 0.9V of 12VIN (Pin 1). This feature allows the chip to power up a PCI slot that can accept boards with widely varying capacitive loads on the supplies. The power-up time will be: C •V t ON ≅ 2 SUPPLY SUPPLY ILIMIT − ILOAD For CSUPPLY = 2000µF, VSUPPLY = 5V, ILIMIT = 7A, ILOAD = 5A, the turn-on time will be ~10ms. 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 will be: • 11.1V C tTIMER = TIMER 22µA For CTIMER = 0.1µF, the timer period will be ~ 50ms. The TIMER pin (Pin 4) is immediately pulled low when ON (Pin 5) 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 chip reaches 150°C, all switches will be latched off and the FAULT pin (Pin 6) will be pulled low. Short-Circuit Protection During a normal power-up sequence, if the TIMER (Pin 4) is done ramping and a supply is still in current limit, all of the pass transistors will be immediately turned off and the FAULT pin (Pin 6) will be pulled low as shown in Figure 4. If a short circuit occurs after the 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 15µs, all of the supplies will be latched off. The 15µs delay prevents quick current 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 ON (Pin 5) is cycled low then high, or the 12VIN pin (Pin 1) power 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 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. The current limit for the 5V and 3.3V supplies is set by placing a sense resistor between 5VIN (Pin 13) and 5VSENSE (Pin 12) and between 3VIN (Pin 9) and 3VSENSE (Pin 10). The current limit will be set by: ILIMIT = 53mV/RSENSE For a 0.005Ω resistor, the current limit will be set at 10.6A and fold back to 1.5A when the output is shorted. For a 0.007Ω resistor, the current limit will be set at 7.6A and fold back to 1.1A when the output is shorted. The current limit for the internal 12V switch is set at 850mA folding back to 250mA and the –12V switch at 450mA folding back to 160mA. 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. R1 should be 20Ω or less to prevent offset errors. A 0.1µF capacitor gives a delay of about 1.5µs and a 1µF capacitor gives a delay of about 15µs. CompactPCI Application The LTC1643L is designed for hot swapping CompactPCI boards. The typical application is shown in Figure 7. The 3.3V, 5V, 12V and –12V inputs to the LTC1643L come from the medium length power pins. The long 3.3V, 5V and V(I/O) pins power up the pull-up resistors, bus precharge 11 LTC1643L/LTC1643L-1/LTC1643H U U W U APPLICATIONS INFORMATION ON 10V/DIV ON 10V/DIV TIMER 10V/DIV TIMER 10V/DIV GATE 10V/DIV GATE 10V/DIV 12VOUT 5V/DIV 12VOUT 5V/DIV 5VOUT 5V/DIV 3VOUT 5V/DIV 3VOUT 5V/DIV 5VOUT 5V/DIV VEEOUT 5V/DIV VEEOUT 5V/DIV FAULT 10V/DIV FAULT 10V/DIV PWRGD 10V/DIV PWRGD 10V/DIV 20ms/DIV 1643 F05 20ms/DIV Figure 4. Power-Up into a Short on 3.3V Output Figure 5. Short Circuit on 5V R1 0.007Ω Q1 IRF7413 5V 5A 5V R2 0.005Ω R4 20Ω Q2 IRF7413 3.3V C2 1µF 9 3VIN R6 10Ω 3.3V 7.6A C3 1µF R3 20Ω 10 R5 10Ω 11 3VSENSE GATE R7 100Ω 3 13 3VOUT 5VIN 12 5VSENSE C1 0.047µF 14 5VOUT LTC1643L 1643 F06 Figure 6. Delay in the Current Limit Loop 12 1643 F04 LTC1643L/LTC1643L-1/LTC1643H U U W U APPLICATIONS INFORMATION R2 0.007Ω 1% MED 5V R1 0.005Ω 1% Q1 IRF7413 5V 5A Q2 IRF7413 3.3V 7.6A MED 3.3V R3 10Ω 5% V(I/O) R8 1.2k 5% R9 2k 5% 12V BD_SEL# HEALTHY# 9 3VIN 1 2 CompactPCI CONNECTOR –12V 5 D2* 12V C6 0.1µF V(I/O) R10 2k 5% R4 10Ω 5% 6 7 C7 0.1µF 10 11 3VSENSE GATE 3 13 3VOUT 5VIN R5 100Ω 5% 12 5VOUT 12VIN 12VOUT VEEIN VEEOUT ON LTC1643L 16 15 12V 500mA –12V 100mA LONG 3.3V PRECHARGE OUT D1 1V ±20% IOUT = ±40mA 1N4148 FAULT PWRGD C1 0.047µF 14 5VSENSE GND TIMER 8 4 C3 0.01µF R11 24Ω 5% C2 0.1µF LONG GND LT1117 R6 130Ω 1% R7 56.2Ω 1% OUT IN ADJ C4 1µF V(I/O) LOCAL_PCI_RESET# PCI_RST# DATA LINE EXAMPLE I/O R14 10Ω, 5% R13 10k 5% I/O LONG LONG 3.3V 5V 3.3V 5V RESET# PCI BRIDGE (21154) DATA BUS *1SMA12CAT3 1643 F07 Figure 7. Typical CompactPCI Application circuit, PCI bridge chip and the LOCAL_PCI_RESET# logic circuitry. The BD_SEL# signal is connected to the ON pin while the PWRGD pin is connected to the HEALTHY# signal. The HEATHLY# signal is combined with the PCI_RESET# signal to generate the LOCAL_PCI_RESET# signal. Capacitors C6 and C7 provide chip bypassing on the 12V and –12V inputs. Diode D2 protects the part from voltage surges below –13.2V on the –12V supply. The 1V precharge voltage for the data bus lines is generated by an LT1117 low dropout regulator. The output of the LT1117 is set to 1.8V, then the voltage is dropped by a 1N4148 diode to generate 1V. The precharge circuit is capable of sourcing and sinking 40mA. LTC1643L-1 The LTC1643L-1 is designed for CompactPCI designs where the ±12V supplies are not being used on the board or the supplies are not well regulated. The power good comparators on the 12VOUT and VEEOUT pins are disabled. The VEEIN pin can be connected to GND and the part will still operate normally if a – 12VOUT output is not needed. However, 12V is still required at the 12VIN pin for the part to function. Refer to Figure 10 for a typical LTC1643L-1 application circuit. Increasing 12V and – 12V Current Capability The internal switches in the LTC1643 are designed for up to 500mA loads on 12V and 200mA on – 12V. If more current is needed, then the circuits in Figure 8 can be used. 13 LTC1643L/LTC1643L-1/LTC1643H U U W U APPLICATIONS INFORMATION For the 12V supply, P-channel transistor Q4 is placed in parallel with the internal switch. When the LTC1643H is turned off, the GATE pin is held low and transistor Q3 is turned on which pulls the gate of Q4 high, turning it off. When the LTC1643H is turned on, the GATE pin goes high, turning off Q3 and allowing R8 to pull the gate of Q4 low to turn it on. For the –12V supply, N-channel transistor Q6 is used to provide the extra load current. When the LTC1643H is turned on, the internal VEE switch is turned on and the –12V output starts to pull down through D1 and turns on Q5. When Q5 turns on, the gate of Q6 starts to rise, turning it on. When the LTC1643H turns off, the VEEOUT pin is pulled up to ground, diode D1 is reversed biased, and transistor Q5 turns off, which allows resistor R10 to turn off Q6. Because Q4 is in parallel with the internal 12V switch, the load current will be shared in proportion to their respective RDS(ON) values. For example, if the RDS(ON) of the external switch is 0.2Ω and the internal switch is 0.4Ω, then, at 1.5A load current, the external switch will provide 1A and the internal switch 500mA. The circuit breaker current will be reached when the internal current reaches 1A and the external current is 2A or 3A load current. The internal –12V switch provides the current limit for the supply, but because the high RDS(ON) of the internal switch (1.2Ω) is in series with D1, very large currents can flow through Q6 before the circuit breaker trips. However, if a short to ground occurs on the –12V output, diode D1 will prevent Q5 from turning on, which will prevent Q6 from turning on. Q4 Si9400 12V 1.5A Q3 TP0610T C3 0.1µF R8 100k Q1 IRF7413 R2 0.005Ω SYSTEM POWER SUPPLY 5V 5A R1 0.007Ω Q2 IRF7413 3.3V 7.6A R6 10Ω GND R5 10Ω 1 8 2 5 PCI POWER SYSTEM CONTROLLER R3 10k R4 10k 6 7 9 12VIN 3VIN 10 11 R7 100Ω 3 3VSENSE GATE 3VOUT 13 5VIN 12 C1 0.047µF 16 5VSENSE 12VOUT GND Q5 TP0610T VEEIN ON FAULT LTC1643H VEEOUT 15 R9 200Ω TIMER D1 1N4148 4 C2 0.1µF PWRGD R10 200Ω Q6 Si9410DY Figure 8. Increasing 12V and – 12V Current Capability 14 –12V 1.5A 1643 F08 LTC1643L/LTC1643L-1/LTC1643H U PACKAGE DESCRIPTION Dimensions in inched (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) 0.189 – 0.196* (4.801 – 4.978) 0.009 (0.229) REF 16 15 14 13 12 11 10 9 0.229 – 0.244 (5.817 – 6.198) 0.150 – 0.157** (3.810 – 3.988) 1 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.007 – 0.0098 (0.178 – 0.249) 2 3 5 6 4 7 0.053 – 0.068 (1.351 – 1.727) 8 0.004 – 0.0098 (0.102 – 0.249) 0° – 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.0250 (0.635) BSC 0.008 – 0.012 (0.203 – 0.305) * 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 GN16 (SSOP) 1098 U TYPICAL APPLICATIONS R1 0.007Ω Q1 IRF7413 5V 5A GND R6 10Ω R7 100Ω SYSTEM POWER SUPPLY C1 0.047µF 9 8 GND 1 12VIN 2 VEEIN 5 ON PCI POWER SYSTEM CONTROLLER R3 10k R4 10k 6 3VIN 13 5VIN 10 12 11 3VSENSE 5VSENSE GATE 3 14 3VOUT 5VOUT 12VOUT LTC1643H VEEOUT FAULT TIMER 7 PWRGD 16 12V 500mA 15 –12V 100mA 4 C2 0.1µF 1643 G09 Figure 9. System Without 3.3V Supply 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. 15 LTC1643L/LTC1643L-1/LTC1643H U TYPICAL APPLICATIONS R2 0.007Ω 1% MED 5V R1 0.005Ω 1% Q1 IRF7413 5V 5A Q2 IRF7413 3.3V 7.6A MED 3.3V R8 1.2k 5% R9 2k 5% 12V 9 3VIN 1 HEALTHY# CompactPCI CONNECTOR 2 BD_SEL# 5 V(I/O) R10 2k 5% R4 10Ω 5% R3 10Ω 5% V(I/O) 6 7 C7 0.1µF 10 11 3VSENSE GATE 3 13 3VOUT 5VIN 12 R5 100Ω 5% 5VOUT 12VIN 12VOUT VEEIN VEEOUT ON LTC1643L-1 16 15 LONG 3.3V PRECHARGE OUT D1 1V ±20% IOUT = ±40mA 1N4148 FAULT PWRGD C1 0.047µF 14 5VSENSE GND TIMER 8 4 C3 0.01µF R11 24Ω 5% C2 0.1µF LONG GND LT1117 R6 130Ω 1% R7 56.2Ω 1% OUT IN ADJ C4 1µF V(I/O) LOCAL_PCI_RESET# PCI_RST# DATA LINE EXAMPLE I/O R14 10Ω, 5% R13 10k 5% LONG LONG 3.3V 5V I/O 3.3V 5V RESET# PCI BRIDGE (21154) DATA BUS *1SMA12CAT3 1643 F10 Figure 10. CompactPCI Application Without ±12V Outputs RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1421 Hot Swap Controller Multiple Supply LTC1422 Hot Swap Controller Single Supply, SO-8 Package LT1640 – 48V Hot Swap Controller Negative High Voltage Supplies, SO-8 Package LTC1642 Fault Protected Hot Swap Controller Operation up to 15V, Handles Surges to 33V 16 Linear Technology Corporation 1643fs, sn1643 LT/TP 0899 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1998