LTC1646 CompactPCI Dual Hot Swap Controller DESCRIPTIO U FEATURES Allows Safe Board Insertion and Removal from a Live, CompactPCITM Bus Controls 3.3V and/or 5V Supplies Programmable Foldback Current Limit During Power-Up Dual Level Circuit Breakers Protect Supplies from Overcurrent and Short-Circuit Faults LOCAL_PCI_RST# Logic On-Chip PRECHARGE Output Biases I/O Pins During Card Insertion and Extraction User Programmable Supply Voltage Power-Up Rate 15V High Side Drive for External N-Channel MOSFETS PWRGD, RESETOUT and FAULT Outputs CompactPCI Bus Removable Boards The LTC(R)1646 is a Hot SwapTM controller that allows a board to be safely inserted and removed from a live CompactPCI bus slot. Two external N-Channel transistors control the 3.3V and 5V supplies. The supplies can be ramped-up in current limit or a programmable rate. Electronic circuit breakers protect both supplies against overcurrent fault conditions. The PWRGD output indicates when all of the supply voltages are within tolerance. The OFF/ON pin is used to cycle the board power or reset the circuit breaker. The PRECHARGE output can be used to bias the bus I/O pins during card insertion and extraction. PCI_RST# is logically combined on-chip with HEALTHY# in order to generate LOCAL_PCI_RST# which can be used to reset the CPCI card logic if either of the supply voltages is not within tolerance. U APPLICATIO S The LTC1646 is available in the 16-pin narrow SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO COMPACT PCI BACKPLANE CONNECTOR (MALE) COMPACT PCI CIRCUIT CARD CONNECTOR (FEMALE) R2 0.007 1% Z2 Z1 Q1 IRF7413 5V 5A 5V R1 0.005, 1% 2.7 LONG 5V 3.3V 3.3V 7.6A 0.1F LONG 3.3V R3 10 V(I/O) 8 3VIN 1.2k 1k BD_SEL# V(I/O) R4 10 3k 15 3 3k 16 PCI_RST# 12 5VIN 11 5VSENSE OFF/ON C1 0.01F 5 5VOUT TIMER 2 10k 0.1F 3VOUT FAULT LTC1646 4 HEALTHY# 9 10 7 3VSENSE GATE 3VOUT R5 1k, 5% PWRGD RESETIN GND 6 3k RESETOUT PRECHARGE 13 18 10k 10 DATA BUS PRECHARGE OUT 1V 10% IOUT = 55mA 1k 12 MMBT2222A DATA LINE EXAMPLE DATA BUS Z1, Z2: BZX84C6V2 DRIVE 14 4.7nF GROUND I/O PIN 1 18 1 LOCAL_PCI_RST# 0.1F 1.8 Q2 IRF7413 3VIN 3VIN 5VIN 3.3V 5V RESET# I/O PCI BRIDGE (21154) 1646 F01 Figure 1 1646fa 1 LTC1646 W W U W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltages: 5VIN, 3VIN ............................................... 10V Input Voltages: (Pins 15, 16) ..................... -0.3V to 10V Output Voltages: (Pins 1, 3, 4) .................. -0.3V to 10V Analog Voltages and Currents: (Pin 9) .................................... -0.3V to (3VIN + 0.3V) (Pins 2, 5, 7, 11, 13, 14) ........ -0.3V to (5VIN + 0.3V) (Pin 10) .......................................................... 20mA Operating Temperature Range: LTC1646C ............................................... 0C to 70C LTC1646I .............................................-40C to 85C Storage Temperature Range ..................-65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C TOP VIEW RESETOUT 1 16 RESETIN TIMER 2 15 OFF/ON FAULT 3 14 DRIVE PWRGD 4 13 PRECHARGE 5VOUT 5 12 5VIN GND 6 11 5VSENSE 3VOUT 7 10 GATE 3VIN 8 9 3VSENSE GN PACKAGE 16-LEAD PLASTIC SSOP TJMAX = 125C, JA = 135C/W ORDER PART NUMBER LTC1646CGN LTC1646IGN GN PART MARKING 1646 1646I Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V5VIN = 5V and V3VIN = 3.3V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX IDD V5VIN Supply Current OFF/ON = 0V VLKO Undervoltage Lockout 5VIN 3VIN VFB Foldback Current Limit Voltage VFB = (V5VIN - V5VSENSE), V5VOUT = 0V, TIMER = 0V VFB = (V5VIN - V5VSENSE), V5VOUT = 4V, TIMER = 0V VFB = (V3VIN - V3VSENSE), V3VOUT = 0V, TIMER = 0V VFB = (V3VIN - V3VSENSE), V3VOUT = 2V, TIMER = 0V VCB Circuit Breaker Trip Voltage t OC UNITS 1.5 4 2.3 2.3 2.50 2.55 2.7 2.7 V V 15 50 15 50 20 55 20 55 30 65 30 65 mV mV mV mV VCB = (V5VIN - V5VSENSE), V5VOUT = 5V, TIMER Open VCB = (V3VIN - V3VSENSE), V3VOUT = 3.3V, TIMER Open 50 50 56 56 65 65 mV mV Overcurrent Fault Response Time (V5VIN - V5VSENSE) = 100mV, TIMER Open (V3VIN - V3VSENSE) = 100mV, TIMER Open 10 10 21 21 30 30 s s t SS Short-Circuit Fault Response Time (V5VIN - V5VSENSE) = 200mV, TIMER Open (V3VIN - V3VSENSE) = 200mV, TIMER Open 0.145 0.145 1 1 s s ICP GATE Pin Output Current OFF/ON = 0V, VGATE = 0V, TIMER = 0V OFF/ON = 5V, VGATE = 5V, TIMER = 0V OFF/ON = 0V, VGATE = 5V, FAULT = 0V, TIMER Open -18 80 4 -13 200 7 -8 300 12 A A mA mA VGATE External Gate Voltage (GATE to GND) OFF/ON = 0V, IGATE = -1A OFF/ON = 0V, V5VIN = 3.3V, IGATE = -1A 12 11 15 13 16 15 V V VTH Power Good Threshold Voltage 3VOUT 5VOUT 2.8 4.5 2.9 4.65 3.0 4.75 V V V3VONLY No 5V Input Mode Window Voltage V3VONLY = V5VIN - V3VIN, V5VOUT = V3VOUT = 3.3V Input Low Voltage OFF/ON, RESETIN, FAULT 50 120 200 mV 0.8 V VIL 1646fa 2 LTC1646 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V5VIN = 5V and V3VIN = 3.3V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VIH Input High Voltage OFF/ON, RESETIN, FAULT MIN 2 VTIMER TIMER Threshold Voltage VTIMER , FAULT = 0V 1.15 IIN OFF/ON Input Current OFF/ON = 5V OFF/ON = 0V RESETIN Input Current TYP MAX UNITS V 1.25 1.35 V 0.08 0.08 10 10 A A RESETIN = 5V RESETIN = 0V 0.08 0.08 10 10 A A 5VSENSE Input Current 5VSENSE = 5V, 5VOUT = 0V 66 100 A 3VSENSE Input Current 3VSENSE = 3.3V, 3VOUT = 0V 66 100 A 3VIN Input Current 3VIN = 3.3V 460 1000 A 5VOUT Input Current 5VOUT = 5V, OFF/ON = 0V 0.9 1.5 mA 3VOUT Input Current 3VOUT = 3.3V, OFF/ON = 0V 0.9 1.5 mA ITIMER TIMER Pin Current OFF/ON = 0V, VTIMER = 0V OFF/ON = 5V, VTIMER = 5V -5 6.6 -3 A mA RDIS 5VOUT Discharge Impedance 3VOUT Discharge Impedance OFF/ON = 5V OFF/ON = 5V 120 120 220 220 VOL Output Low Voltage FAULT, PWRGD, RESETOUT, I = 2mA 0.25 0.4 V VPXG PRECHARGE Reference Voltage VPRECHARGE, V5VIN = 5V and 3.3V 1.00 1.10 V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. -7 0.90 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 PERFOR A CE CHARACTERISTICS 12 11 11 10 10 9 9 8 7 6 5 4 3 1.8 1.7 SUPPLY CURRENT (mA) 12 8 7 6 5 4 3 2 2 0 0 1 3 2 4 OUTPUT VOLTAGE (V) 5 1646 G01 0 1 3 2 OUTPUT VOLTAGE (V) 4 1.6 1.5 1.4 1.3 1.2 1.1 RSENSE = 0.005 1 RSENSE = 0.007 1 0 5VIN Supply Current vs Temperature 3.3V Current Foldback Profile OUTPUT CURRENT (A) OUTPUT CURRENT (A) 5V Current Foldback Profile 5 1646 G02 1.0 -50 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G03 1646fa 3 LTC1646 U W TYPICAL PERFOR A CE CHARACTERISTICS 5VIN Undervoltage Lockout Voltage vs Temperature 3VIN Undervoltage Lockout Voltage vs Temperature 2.60 2.55 LOW-TO-HIGH TRANSITION 2.50 HIGH-TO-LOW TRANSITION 2.45 2.40 -50 -25 0 25 50 TEMPERATURE (C) 75 60 LOW-TO-HIGH TRANSITION 2.55 HIGH-TO-LOW TRANSITION 2.50 2.45 2.40 -50 100 -25 0 25 50 TEMPERATURE (C) 75 1646 G04 30 3VOUT = 0V 10 0 -50 -25 0 25 50 TEMPERATURE (C) 75 58 57 56 55 54 53 52 51 -25 0 25 50 TEMPERATURE (C) 75 21.00 20.75 20.50 20.25 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G10 100 58 57 56 55 54 53 52 51 50 -50 100 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G09 Gate Current vs Temperature 170 -10 160 -11 150 GATE CURRENT (A) SHORT-CIRCUIT FAULT RESPONSE TIME (ns) 21.25 75 59 5VIN/3VIN Short-Circuit Fault Response Time vs Temperature 21.50 0 25 50 TEMPERATURE (C) 1646 G08 5VIN/3VIN Overcurrent Fault Response Time vs Temperature 21.75 -25 60 1646 G07 20.00 -50 10 3VIN Circuit Breaker Trip Voltage vs Temperature 59 50 -50 100 22.00 5VOUT = 0V 20 1646 G06 CIRCUIT BREAKER TRIP VOLTAGE (mV) 40 20 30 0 -50 100 60 CIRCUIT BREAKER TRIP VOLTAGE (mV) FOLDBACK CURRENT LIMIT VOLTAGE (mV) 60 50 40 5VIN Circuit Breaker Trip Voltage vs Temperature 3VOUT = 2V 5VOUT = 4V 50 1646 G05 3VIN Foldback Current Limit Voltage vs Temperature OVERCURRENT FAULT RESPONSE TIME (s) FOLDBACK CURRENT LIMIT VOLTAGE (mV) UNDERVOLTAGE LOCKOUT VOLTAGE (V) UNDERVOLTAGE LOCKOUT VOLTAGE (V) 2.60 5VIN Foldback Current Limit Voltage vs Temperature 140 130 120 -12 -13 -14 110 100 -50 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G11 -15 -50 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G12 1646fa 4 LTC1646 U W TYPICAL PERFOR A CE CHARACTERISTICS Gate ISINK vs Temperature 15.5 3.00 FAULT = 0V POWER GOOD THRESHOLD VOLTAGE (V) 10 I = -1A 5VIN = 5V 15.0 GATE VOLTAGE (V) 9 GATE ISINK (mA) Power Good Threshold Voltage vs Temperature (3VOUT) Gate Voltage vs Temperature 8 7 14.5 14.0 13.5 5VIN = 3.3V 6 13.0 5 -50 -25 0 25 50 TEMPERATURE (C) 75 12.5 -50 100 -25 0 25 50 TEMPERATURE (C) 75 1646 G13 2.90 2.85 2.80 -50 100 -25 0 25 50 TEMPERATURE (C) 75 1646 G14 4.75 100 1646 G15 5VSENSE Input Current vs Temperature Timer Threshold Voltage vs Temperature Power Good Threshold Voltage vs Temperature (5VOUT) 1.30 70 4.70 4.65 4.60 4.55 5VSENSE INPUT CURRENT (A) 69 TIMER THRESHOLD VOLTAGE (V) POWER GOOD THRESHOLD VOLTAGE (V) 2.95 1.28 1.26 1.24 1.22 68 67 66 65 64 63 62 61 4.50 -50 -25 0 25 50 TEMPERATURE (C) 75 100 1.20 -50 -25 0 25 50 TEMPERATURE (C) 75 1646 G16 3VIN INPUT CURRENT (A) 3VSENSE INPUT CURRENT (A) 69 66 65 64 63 62 480 -4.00 475 -4.25 470 465 460 455 450 61 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G19 75 445 -50 100 Timer Current vs Temperature TIMER CURRENT (A) 70 67 0 25 50 TEMPERATURE (C) 1646 G18 3VIN Input Current vs Temperature 68 -25 1646 G17 3VSENSE Input Current vs Temperature 60 -50 60 -50 100 -4.50 -4.75 -5.00 -5.25 -5.50 -5.75 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G20 -6.00 -50 -25 0 25 50 TEMPERATURE (C) 75 100 1646 G21 1646fa 5 LTC1646 U W TYPICAL PERFOR A CE CHARACTERISTICS RESETOUT, PWRGD and FAULT Output Low Voltage vs ISINK 5VOUT/3VOUT Discharge Impedance vs Temperature 180 3VOUT/5VOUT DISCHARGE IMPEDANCE () 1.0 OUTPUT LOW VOLTAGE (V) 0.9 90C 0.8 0.7 25C 0.6 0.5 -45C 0.4 0.3 0.2 0.1 0 0 1 2 3 ISINK (mA) 4 5 160 140 120 100 80 60 40 20 0 -50 -25 0 25 50 TEMPERATURE (C) 1646 G22 75 100 1646 G23 U U U PI FU CTIO S RESETOUT (Pin 1): Open Drain Digital Output. Connect the CPCI LOCAL_PCI_RST# signal to the RESETOUT pin. RESETOUT is the logical combination of RESETIN and PWRGD (see Table 4). TIMER (Pin 2): Current Fault Inhibit Timing Input. Connect a capacitor from TIMER to GND. With the chip turned off, the TIMER pin is internally held at GND. When the chip is turned on, a 5A pull-up current source is connected to TIMER. Current limit and voltage compliance faults will be ignored until the voltage at the TIMER pin is greater than 1.25V. FAULT (Pin 3): Open Drain Digital I/O. FAULT is pulled low when a current limit fault is detected. Faults are ignored while the voltage at the TIMER pin is less than 1.25V. Once the TIMER cycle is complete, FAULT will pull low and the chip will latch off in the event of an overcurrent fault. The chip will remain latched in the off state until the OFF/ON pin is cycled high then low or the power is cycled. Forcing the FAULT pin low with an external pull-down will cause the chip to be latched into the off state after a 21s deglitching time. PWRGD (Pin 4) :Open Drain Power Good Digital Output. Connect the CPCI HEALTHY# signal to the PWRGD pin. PWRGD remains low while V3VOUT 2.9V and V5VOUT 4.65V. When either of the supplies falls below its power good threshold voltage, PWRGD will go high after a 50s deglitching time. 5VOUT (Pin 5): 5V Output Sense. The PWRGD pin will not pull low until the 5VOUT pin voltage exceeds 4.65V. If no 5V input supply is available, tie the 5VOUT pin to the 3VOUT pin in order to disable the 5VOUT power good function. GND (Pin 6): Chip Ground 3VOUT (Pin 7): 3.3V Output Sense. The PWRGD pin will not pull low until the 3VOUT pin voltage exceeds 2.90V. If no 3.3V input supply is available, tie the 3VOUT pin to the 5VOUT pin. 3VIN (Pin 8): 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, connect a diode between 5VIN and 3VIN (tie anode to 5VIN and cathode to 3VIN ). See Figure 11. 1646fa 6 LTC1646 U U U PI FU CTIO S 3VSENSE (Pin 9): 3.3V Current Limit Set. 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 while the TIMER pin voltage is less than 1.25V. A foldback feature makes the current limit decrease as the voltage at the 3VOUT pin approaches GND. When the TIMER pin voltage is greater than 1.25V, the circuit breaker function is enabled. If the voltage across the sense resistor exceeds 56mV but is less than 150mV, the circuit breaker is tripped after a 21s time delay. In the event the sense resistor voltage exceeds 150mV, the circuit breaker trips immediately and the chip latches off. To disable the 5V current limit, short 5VSENSE and 5VIN together. When the TIMER pin voltage exceeds 1.25V, the circuit breaker function is enabled. If the voltage across the sense resistor exceeds 56mV, the circuit breaker is tripped after a 21s time delay. In the event the sense resistor voltage exceeds 150mV, the circuit breaker trips immediately and the chip latches off. To disable the 3.3V current limit, 3VSENSE and 3VIN can be shorted together. 5VIN (Pin 12): 5V Supply Sense Input. An undervoltage lockout circuit prevents the GATE pin voltage from ramping up when the voltage at the 5VIN pin is less than 2.5V. If no 5V input supply is available, tie the 5VIN pin to the 3VIN pin. GATE (Pin 10): High Side Gate Drive for the External 3.3V and 5V N-Channel pass transistors. 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 13A current source connected to the internal charge pump 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 supply lines. During power-down, the slope of the ramp down voltage is set by the 200A current source connected to GND and the external GATE capacitor. 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 while the TIMER pin voltage is less than 1.25V. If a current fault occurs after the TIMER pin voltage exceeds 1.25V, the GATE pin is immediately pulled to GND. 5VSENSE (Pin 11): 5V Current Limit Set. 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 while the TIMER pin voltage is less than 1.25V. A foldback feature makes the current limit decrease as the voltage at the 5VOUT pin approaches GND. PRECHARGE (Pin 13): Precharge Monitor Input. An onchip error amplifier with a 1V reference servos the DRIVE pin voltage to keep the precharge node at 1V. If the precharge function is not being used, tie the PRECHARGE pin to GND. DRIVE (Pin 14): Precharge Base Drive Output. Provides base drive for an external NPN emitter-follower which in turn biases the PRECHARGE node. If the precharge function is not being used, allow the DRIVE pin to float. OFF/ON (Pin 15): Digital Input. Connect the CPCI BD_SEL# signal to the OFF/ON pin. When the OFF/ON pin is pulled low, the GATE pin is pulled high by a 13A current source. When the OFF/ON pin is pulled high the GATE pin will be pulled to ground by a 200A current source. The OFF/ON pin is also used to reset the electronic circuit breaker. If the OFF/ON pin is cycled high and low following the trip of the circuit breaker, the circuit breaker is reset, and a normal power-up sequence will occur. RESETIN (Pin 16): Digital Input. Connect the CPCI PCI_RST# signal to the RESETIN pin. Pulling RESETIN low will cause the RESETOUT pin to pull low. 1646fa 7 LTC1646 W TEST DIAGRA V3VONLY No 5V Input Mode Window Voltage V3VONLY = 5VIN - 3VIN 5VOUT = 3VOUT = 3.3V, 3VIN = 3.3V V3VONLY V5VIN 3.3V -V3VONLY 5V PWRGD 0V 1646 T01 W UW TI I G DIAGRA S tOC Overcurrent Fault Detect FALL TIME 1s, 5VIN = 5V, 3VIN = 3.3V 5V V5VSENSE OR 3.3V 100mV OR V3VSENSE tOC FAULT 1V 1646 T02 tSC Short-Circuit Fault Detect FALL TIME 30ns, 5VIN = 5V, 3VIN = 3.3V 5V V5VSENSE OR 3.3V 200mV OR V3VSENSE tSC FAULT 1V 1646 T03 1646fa 8 LTC1646 W BLOCK DIAGRA 5VIN 5VSENSE 12 11 GATE 10 VGG 5VOUT +- 3VIN 9 8 + 7 5 -+ 55mV 55mV +- - Q1 200A -+ - + + - - 150mV +- 3VOUT 5VOUT 3VOUT 13A + 3VSENSE Q2 Q3 150mV 2.5V UVL -+ 2.5V UVL CP3 + OFF/ON 15 - FAULT 3 REF Q7 CP4 + PWRGD 4 LOGIC - Q6 1 RESETOUT REF Q4 RESETIN 16 5Vin 5A + TIMER 2 1V Q5 - 6 GND 14 13 DRIVE PRECHARGE 1646 BD U W U U APPLICATIO S I FOR ATIO Hot Circuit Insertion When a circuit board is inserted into a live CompactPCI (CPCI) slot, the supply bypass capacitors on the board can draw huge supply transient currents from the CPCI power bus as they charge up. The transient currents can cause glitches on the power bus, causing other boards in the system to reset. The LTC1646 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 CPCI slot without glitching the system power supplies. The chip also protects the supplies from shorts, precharges the bus I/O pins during insertion and extraction and monitors the supply voltages. The LTC1646 is specifically designed for CPCI applications where the chip resides on the plug-in board. LTC1646 Feature Summary 1. Allows safe board insertion and removal from a CPCI backplane. 2. Controls 5V and 3.3V CPCI supplies. 3. Current limit during power-up: the supplies are allowed to power up in current limit. This 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 and an external capacitor. 1646fa 9 LTC1646 U W U U APPLICATIO S I FOR ATIO 4. 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. 5. Dual-level, programmable 5V and 3.3V circuit breakers: this feature is enabled when the TIMER pin voltage exceeds 1.25V. If either supply exceeds current limit for more than 21s, the circuit breaker will trip, the supplies will be turned off, and the FAULT pin is pulled low. In the event that either supply exceeds three times the set current limit, all supplies will be turned off and the FAULT pin is pin is pulled low without delay. 6. 15V high side drive for external 3.3V and 5V N-channel MOSFETs. 7. PWRGD output: monitors the voltage status of the supply voltages. 8. PCI_RST# combined on-chip with HEALTHY# to create LOCAL_PCI_RST# output. If HEALTHY# deasserts, LOCAL_PCI_RST# is asserted independent of PCI_RST#. 9. Precharge output: on-chip reference and amplifier provide 1V for biasing bus I/O connector pins during CPCI card insertion and extraction. 10. Space saving 16-pin SSOP package. PCI Power Requirements CPCI systems may require up to four power rails: 5V, 3.3V, 12V and -12V. The LTC1646 is designed for CPCI applications which only use the 5V and/or 3.3V supplies. 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 5% < 3000F 3.3V 0.3V < 3000F 5V 3.3V The main 3.3V and 5V inputs to the LTC1646 come from the medium length power pins. The long 3.3V, 5V connector pins are shorted to the medium length 5V and 3.3V connector pins on the CPCI plug-in card and provide early power for the LTC1646's precharge circuitry, the V(I/O) pull-up resistors and the PCI bridge chip. The BD_SEL# signal is connected to the OFF/ON pin while the PWRGD pin is connected to the HEALTHY# signal. The HEALTHY# signal is combined with the PCI_RST# signal on-chip to generate the LOCAL_PCI_RST# signal which is available at the RESETOUT pin. The power supplies are controlled by placing external N-channel pass transistors in the 3.3V and 5V power paths. Resistors R1 and R2 provide current fault detection and R5 and C1 provide current control loop compensation. Resistors R3 and R4 prevent high frequency oscillations in Q1 and Q2. When the CPCI card is inserted, the long 5V and 3.3V connector pins and GND pins make contact first. The LTC1646's precharge circuit biases the bus I/O pins to 1V during this stage of the insertion (Figure 2). The 5V and 3.3V medium length pins make contact during the next stage of insertion, but the slot power is disabled as long as the OFF/ON pin is pulled high by the 1.2k pull-up resistor to V(I/O). During the final stage of board insertion, the BD_SEL# short connector pin makes contact and the OFF/ON pin can be pulled low. This enables the pass transistors to turn on and a 5A current source is connected to the TIMER pin. The current in each pass transistor increases until it reaches the current limit for each supply. The 5V and 3.3V supplies are then allowed to power up based on one of the following power-up rates: ILIMIT (3 V) ILIMIT (5 V) dV 13A = , or = , or = (1) dt C1 C LOAD(5 VOUT ) C LOAD(3 VOUT ) whichever is slower. Power-Up Sequence The LTC1646 is specifically designed for hot swapping CPCI boards. The typical application is shown in Figure 1. Current limit faults are ignored while the TIMER pin voltage is ramping up and is less than 1.25V. Once both supply voltages are within tolerance, HEALTHY# will pull low and LOCAL_PCI_RST# is free to follow PCI_RST#. 1646fa 10 LTC1646 U W U U APPLICATIO S I FOR ATIO GATE 10V/DIV GATE 10V/DIV 5VOUT 3VOUT 5V/DIV 5VOUT 3VOUT 5V/DIV TIMER 5V/DIV TIMER 5V/DIV BD_SEL# 5V/DIV BD_SEL# 5V/DIV HEALTHY# 5V/DIV LCL_PCI_RST# 5V/DIV HEALTHY# 5V/DIV LCL_PCI_RST# 5V/DIV PRECHARGE 5V/DIV PRECHARGE 5V/DIV 20ms/DIV 10ms/DIV 1646 F02 Figure 2. Normal Power-Up Sequence Power-Down Sequence When BD_SEL# is pulled high, 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 2) is immediately pulled low. The GATE pin (Pin 10) is pulled down by a 200A current source to prevent the load currents on the 3.3V and 5V supplies from going to zero instantaneously in order to prevent glitching the power supply voltages. When either of the output voltages dips below its threshold, HEALTHY# pulls high and LOCAL_PCI_RST# will be asserted low. Once the power-down sequence is complete, the CPCI card may be removed from the slot. During extraction, the precharge circuit will continue to bias the bus I/O pins at 1V until the 5V and 3.3V long connector pin connections are separated. Timer During a power-up sequence, a 5A current source is connected to the TIMER pin and current limit faults are ignored until the voltage exceeds 1.25V. This feature 1646 F03 Figure 3. Normal Power-Down Sequence allows the chip to power up CPCI boards with widely varying capacitive loads on the supplies. The power-up time for either of the two outputs is given by: tON (XVOUT ) = 2 * CLOAD(XVOUT) * XVOUT ILIMIT(XVOUT) - ILOAD(XVOUT) (2) Where XVOUT = 5VOUT or 3VOUT. For example, for CLOAD(5VOUT) = 2000F, ILIMIT = 7A, and ILOAD = 5A, the 5VOUT turn-on time will be ~10ms. By substituting the variables in Equation 2 with the appropriate values, the turn-on time for the 3VOUT output can also 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 for the LTC1646 is given by: tTIMER = C TIMER * 1.25V 5A (3) As a design aid, the timer period as a function of the timing capacitor using standard values from 0.01F to 1F is shown in Table 2. 1646fa 11 LTC1646 U W U U APPLICATIO S I FOR ATIO Table 2. t TIMER vs CTIMER CTIMER tTIMER CTIMER tTIMER 0.01F 2.5ms 0.22F 55ms 0.022F 5.5ms 0.33F 82.5ms 0.033F 8.25ms 0.47F 118ms 0.047F 11.8ms 0.68F 170ms 0.068F 17ms 0.82F 205ms 0.082F 20.5ms 1F 250ms 0.1F 25ms The TIMER pin is immediately pulled low when BD_SEL# goes high. 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 prevents voltage glitches at the input supply when powering up into a short circuit. After power-up (TIMER pin voltage >1.25V), the 5V and 3.3V supplies are protected from overcurrent and shortcircuit conditions by dual-level circuit breakers. If the sense resistor voltage of either supply current exceeds 56mV but is less than 150mV, an internal timer is started. If the supply is still overcurrent after 21s, the circuit breaker trips and both supplies are turned off (Figure 5). Short-Circuit Protection During a normal power-up sequence, if the TIMER pin is done ramping and a supply is still in current limit, all of the pass transistors will be immediately turned off and FAULT (Pin 3) will be pulled low as shown in Figure 4. In order 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. GATE 5V/DIV 5VIN - 5VSENSE 50mV/DIV GATE 10V/DIV FAULT 5V/DIV 5VOUT 3VOUT 2V/DIV 10s/DIV TIMER 1V/DIV 1646 F05 Figure 5. Overcurrent Fault on 5V BD_SEL# 5V/DIV If a short-circuit occurs and the sense resistor voltage of either supply current exceeds 150mV, the circuit breakers trip without delay and the chip latches off (Figure 6). The chip will stay in the latched-off state until OFF/ON (Pin 15) is cycled high then low, or the 5VIN (Pin 12) power supply is cycled. LCL_PCI_RST# 5V/DIV HEALTHY# 5V/DIV FAULT 5V/DIV 10ms/DIV Figure 4. Power-Up into a Short on 3.3V Output 1646 F04 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 3VOUT and R2 for 5VOUT, see Figure 1). As shown in Figure 1, a sense resistor is connected between 1646fa 12 LTC1646 U W U U APPLICATIO S I FOR ATIO Calculating RSENSE An equivalent circuit for one of the LTC1646's circuit breakers useful in calculating the value of the sense resistor is shown in Figure 7. To determine the most appropriate value for the sense resistor first requires the maximum current required by the load under worst-case conditions. 5VIN -5VSENSE 100mV/DIV ILOAD(MAX) GATE 10V/DIV 5VIN 1 RSENSE 3 4 11 5VSENSE 12 5VIN + - FAULT 5V/DIV - 5s/DIV 2 VCB LTC1646* + 1646 F06 Figure 6. Short-Circuit Fault on 5V *ADDITIONAL DETAILS OMITTED FOR CLARITY 5VIN (Pin 12) and 5VSENSE (Pin 11) for the 5V supply. For the 3.3V supply, a sense resistor is connected between 3VIN (Pin 8) and 3VSENSE (Pin 9). The current limit and the current foldback current level are given by Equations 4 and 5: ILIMIT (XVOUT) = (4) 55mV RSENSE(XVOUT) IFOLDBACK(XVOUT) = (5) 20mV RSENSE(XVOUT) where XVOUT = 5VOUT or 3VOUT. As a design aid, the current limit and foldback level for commonly used values for RSENSE is shown in Table 3. Table 3. ILIMIT(XVOUT) and IFOLDBACK(XVOUT) vs RSENSE RSENSE () ILIMIT(XVOUT) IFOLDBACK(XVOUT) 0.005 11A 4A 0.006 9.2A 3.3A 0.007 7.9A 2.9A 0.008 6.9A 2.5A 0.009 6.1A 2.2A 0.01 5.5A 2A where XVOUT = 3VOUT or 5VOUT. VCB(MAX) = 65mV VCB(NOM) = 56mV VCB(MIN) = 50mV 1646 F07 Figure 7. Circuit Breaker Equivalent Circuit for Calculating RSENSE Two other parameters affect the value of the sense resistor. First is the tolerance of the LTC1646's circuit breaker threshold. The LTC1646's nominal circuit breaker threshold is VCB(NOM) = 56mV; however, it exhibits a -6mV/+9mV tolerance due to process variations. Second is the tolerance (RTOL) in the sense resistor. Sense resistors are available in RTOLs of 1%, 2% and 5% and exhibit temperature coefficients of resistance (TCRs) between 75ppm/C and 100ppm/C. How the sense resistor changes as a function of temperature depends on the I2R power being dissipated by it. The first step in calculating the value of RSENSE is based on ITRIP(MAX) and the lower limit for the circuit breaker threshold, VCB(MIN). The maximum value for RSENSE in this case is expressed by Equation 6: RSENSE(MAX) = VCB(MIN) ITRIP(MAX) (6) The second step is to determine the nominal value of the sense resistor which is dependent on its tolerance 1646fa 13 LTC1646 U W U U APPLICATIO S I FOR ATIO (RTOL = 1%, 2% or 5%) and standard sense resistor values. Equation 7 can be used to calculate the nominal value from the maximum value found by Equation 6: RSENSE(NOM) = RSENSE(MAX) RTOL 1+ 100 (7) Often, the result of Equation 7 may not yield a standard sense resistor value. In this case, two sense resistors with the same RTOL can be connected in parallel to yield RSENSE(NOM). The last step requires calculating a new value for ITRIP(MAX)(ITRIP(MAX, NEW)) based on a minimum value for RSENSE (RSENSE(MIN)) and the upper limit for the circuit breaker threshold, VCB(MAX). Should the calculated value for ITRIP(MAX, NEW) be much greater than the design value for ITRIP(MAX), a larger sense resistor value should be selected and the process repeated. The new value for ITRIP(MAX, NEW) is given by Equation 8: ITRIP(MAX,NEW) VCB(MAX) = RSENSE(MIN) (8) RTOL where RSENSE(MIN) = RSENSE(NOM) * 1 - 100 Example: A 5V supply exhibits a nominal 5A load with a maximum load current of 6.8A (ILOAD(MAX) = 6.8A), and sense resistors with 5% RTOL will be used. According to Equation 6, VCB(MIN) = 50mV and RSENSE(MAX) is given by: RSENSE(MAX) = VCB(MIN) ITRIP(MAX) = 50mV = 0.0074 6.8A The nominal sense resistor value is (Equation 7): RSENSE(NOM) = RSENSE(MAX) 0.0074 = = 0.007 RTOL 5 1+ 1+ 100 100 And the new current-limit trip point is Equation 8: ITRIP(MAX,NEW) = VCB(MAX) = RSENSE(MIN) VCB(MAX) 65mV = = 9.8A RTOL 0.0065 RSENSE(N0M) * 1 - 100 Since ITRIP(MAX, NEW) > ILOAD(MAX), a larger value for RSENSE should be selected and the process repeated again to lower ITRIP(MAX, NEW) without substantially affecting ILOAD(MAX). Output Voltage Monitor The status of both 5V and 3.3V output voltages is monitored by the power good function. In addition, the PCI_RST# signal is logically combined on-chip with the HEALTHY# signal to create LOCAL_PCI_RST# (see Table 4). Table 4. LOCAL_PCI_RST# Truth Table PCI_RST# HEALTHY# LOCAL_PCI_RST# LO LO LO LO HI LO HI LO HI HI HI LO If either of the output voltages drop below the power good threshold for more than 50s, the HEALTHY# signal will be pulled high and the LOCAL_PCI_RST# signal will be pulled low. Precharge The PRECHARGE input and DRIVE output pins are intended for use in generating the 1V precharge voltage that is used to bias the bus I/O connector pins during board insertion. The LTC1646 is also capable of generating precharge voltages other than 1V. Figure 8 shows a circuit that can be used in applications requiring a precharge voltage less than 1V. The circuit in Figure 9 can be used for applications that need precharge voltages greater than 1V. Table 5 lists suggested resistor values for R1 and R2 vs precharge voltage for the application circuits shown in Figures 8 and 9. 1646fa 14 LTC1646 U W U U APPLICATIO S I FOR ATIO Table 5. R1 and R2 Resistor Values vs Precharge Voltage VPRECHARGE R1 R2 VPRECHARGE 1.5V 18 9.09 1.4V 18 1.3V 1.2V Other CompactPCI Applications R1 R2 0.9V 16.2 1.78 7.15 0.8V 14.7 3.65 18 5.36 0.7V 12.1 5.11 18 3.65 0.6V 11 7.15 1.1V 18 1.78 0.5V 9.09 9.09 1V 18 0 The LTC1646 can be easily configured for applications where no 5V supply is present by simply tying the 5VIN and 5VSENSE pins to the 3VIN pin and tying the 5VOUT pin to the 3VOUT pin (Figure 10). LTC1646* GND 6 LTC1646* PRECHARGE DRIVE 13 14 4.7nF 18 GND 6 PRECHARGE 13 1k DRIVE 14 4.7nF 18 1k 12 R1 R2 12 MMBT2222A R1 PRECHARGE OUT R1 VPRECHARGE = * 1V R1 + R2 3VIN *ADDITIONAL DETAILS OMITTED FOR CLARITY COMPACT PCI CIRCUIT CARD CONNECTOR (FEMALE) Z1 3VIN 3 0.1F IRF7413 3.3VOUT 7.6A 4 1.8 10 V(I/O) 1k 8 3VIN 1.2k 1k BD_SEL# 15 9 10 7 3VSENSE GATE 3VOUT 12 5VIN 11 5VSENSE OFF/ON 0.010F 5 5VOUT TIMER 2 10k V(I/O) 3k 1646 F09 Figure 9. Precharge Voltage >1V Application Circuit 0.005 1 1% 2 3.3V LONG 3.3V MMBT2222A *ADDITIONAL DETAILS OMITTED FOR CLARITY 1646 F08 Figure 8. Precharge Voltage <1V Application Circuit COMPACT PCI BACKPLANE CONNECTOR (MALE) R2 PRECHARGE OUT R1 + R2 VPRECHARGE = * 1V R1 3k 3 0.1F 3VOUT FAULT LTC1646 16 PCI_RST# 3k PWRGD RESETIN GND 6 RESETOUT PRECHARGE 13 4.7nF DRIVE 14 18 1k 18 12 GROUND 1k PRECHARGE OUT 1V 10% IOUT = 55mA 10 3VIN MMBT2222A DATA LINE EXAMPLE I/O PIN 1 DATA BUS 1 LOCAL_PCI_RST# 4 HEALTHY# DATA BUS Z1: BZX84C6V2 3.3V 3VIN RESET# I/O PCI BRIDGE (21154) 1646 F10 Figure 10. 3.3V Supply Only Typical Application 1646fa 15 LTC1646 U W U U APPLICATIO S I FOR ATIO COMPACT PCI COMPACT PCI BACKPLANE CIRCUIT CARD CONNECTOR CONNECTOR (MALE) (FEMALE) Z1 0.007 5VIN 1 5V 3 LONG 5V 2 IRF7413 5VOUT 4 2.7 10 BAV16W 1k 0.1F 0.01F 8 9 12 11 10 5 7 3VIN 3VSENSE 5VIN 5VSENSE GATE 5VOUT 3VOUT 6 GND GND LTC1646 Z1: BZX84C6V2 1646 F11 Figure 11. 5V Supply Only Typical Application If no 3.3V supply is present, Figure 11 illustrates how the LTC1646 should be configured. First, 3VSENSE (Pin 9) is connected to 3VIN (Pin 8), 3VOUT (Pin 7) is connected to 5VOUT (Pin 5) and the LTC1646's 3VIN pin is connected through a diode (BAV16W) to 5VIN. For applications where the BD_SEL# connector pin is typically grounded on the backplane, the circuit in Figure 12 allows the LTC1646 to be reset simply by pressing a pushbutton switch on the CPCI plug-in board. This arrangement eliminates the requirement to extract and reinsert the CPCI board in order to reset the LTC1646's circuit breakers. PUSHBUTTON SWITCH V(I/0) COMPACT PCI COMPACT PCI BACKPLANE CIRCUIT CARD CONNECTOR CONNECTOR (MALE) (FEMALE) 1.2k BD_SEL# 15 100 Overvoltage Transient Protection Good engineering practice calls for bypassing the supply rail of any analog circuit. Bypass capacitors are often placed at the supply connection of every active device, in addition to one or more large-value bulk bypass capacitors per supply rail. If power is connected abruptly, the large bypass capacitors slow the rate of rise of the supply voltage and heavily damp any parasitic resonance of lead or PC trace inductance working against the supply bypass capacitors. The opposite is true for LTC1646 Hot Swap circuits mounted on plug-in cards. In most cases, there is no supply bypass capacitor present on the powered 3.3V or 5V side of the MOSFET switch. An abrupt connection, produced by inserting the board into a backplane connector, results in a fast rising edge applied on the 3.3V and the 5V line of the LTC1646. OFF/ON 1k LTC1646 LONG GND 6 GND 1646 F12 Figure 12. BD_SEL# Pushbutton Toggle Switch 1646fa 16 LTC1646 U W U U APPLICATIO S I FOR ATIO Since there is no bulk capacitance to damp the parasitic trace inductance, supply voltage transients excite parasitic resonant circuits formed by the power MOSFET capacitance and the combined parasitic inductance from the wiring harness, the backplane and the circuit board traces. These ringing transients appear as a fast edge on the 3.3V or 5V supply, exhibiting a peak overshoot to 2.5 times the steady-state value followed by a damped sinusoidal response whose duration and period is dependent on the resonant circuit parameters. Since the absolute maximum supply voltage of the LTC1646 is 10V, transient protection against 3.3V and 5V supply voltage spikes and ringing is highly recommended. LTC1646 circuit schematics, Zener diodes and snubber networks have been added to each 3.3V and 5V supply rail and should be used always. These protection networks should be mounted very close to the LTC1646's supply voltage using short lead lengths to minimize lead inductance. This is shown schematically in Figure 13 and a recommended layout of the transient protection devices around the LTC1646 is shown in Figure 14. 9 10 11 12 13 14 15 16 5VIN TZ1 In these applications, there are two methods for eliminating these supply voltage transients: using Zener diodes to clip the transient to a safe level and snubber networks. Snubbers are RC networks whose time constants are large enough to safely damp the inductance of the board's parasitic resonant circuits. As a starting point, the shunt capacitors in these networks are chosen to be 10x to 100x the power MOSFET's COSS under bias. The value of the series resistor (R6 and R7 in Figure 13) is then chosen to be large enough to damp the resulting series R-L-C circuit and typically ranges from 1 to 10. Note that in all VIN1 5V LONG 5V VIN2 3.3V LONG 3.3V R1 0.005 8 6 5 4 3 2 1 7 3VIN GND *ADDITIONAL DETAILS OMITTED FOR CLARITY DRAWING IS NOT TO SCALE! Q1 IRF7413 5VOUT AT 5A Q2 IRF7413 9 10 3VSENSE GATE Z1 3VOUT AT 7.6A R4 10 7 12 3VOUT 5VIN 11 5VSENSE R5 1k 5 GND Z1, Z2: BZX84C6V2 **ADDITIONAL DETAILS OMITTED FOR CLARITY C1 0.01F 5VOUT LTC1646** C2 0.1F 1646 F14 Figure 14. Recommended Layout for Transient Protection Components R3 10 8 C3 TZ2 R7 1.8 3VIN VIAS TO GND PLANE LTC1646* R2 0.007 R6 2.7 C2 6 Z2 C3 0.1F 1646 F13 Figure 13. Place Transient Protection Device Close to the LTC1646 1646fa 17 LTC1646 U W U U APPLICATIO S I FOR ATIO In the majority of applications, it will be necessary to use plated-through vias to make circuit connections from component layers to power and ground layers internal to the PC board. For 1 ounce copper foil plating, a general rule is 1A of DC current per via, making sure the via is properly dimensioned so that solder completely fills any void. For other plating thicknesses, check with your PCB fabrication facility. PCB Layout Considerations For proper operation of the LTC1646's circuit breaker function, a 4-wire Kelvin connection to the sense resistors is highly recommended. A recommended PCB layout for the sense resistor, the power MOSFET, and the GATE drive components around the LTC1646 is illustrated in Figure 15. In Hot Swap applications where load currents can reach 10A, narrow PCB tracks exhibit more resistance than wider tracks and operate at more elevated temperatures. Since the sheet resistance of 1 ounce copper foil is , track resistances add up quickly approximately 0.5m/ in high current applications. Thus, to keep PCB track resistance and temperature rise to a minimum, the suggested trace width in these applications for 1 ounce copper foil is 0.03" for each ampere of DC current. Power MOSFET and Sense Resistor Selection Table 6 lists some current MOSFET transistors that are available and Table 7 lists some current sense resistors that can be used with the LTC1646's circuit breakers. Table 8 lists supplier web site addresses for discrete component mentioned throughout the LTC1646 data sheet. Table 6. N-Channel Power MOSFET Selection Guide CURRENT LEVEL (A) PART NUMBER DESCRIPTION MANUFACTURER 0 to 2 MMDF3N02HD Dual N-Channel SO-8 RDS(ON) = 0.1 ON Semiconductor 2 to 5 MMSF5N02HD Single N-Channel SO-8 RDS(ON) = 0.025 ON Semiconductor 5 to 10 MTB50N06V Single N-Channel DD Pak RDS(ON) = 0.028 ON Semiconductor 5 to 10 IRF7413 Single N-Channel SO-8 RDS(ON) = 0.01 International Rectifier 5 to 10 Si4410DY Single N-Channel SO-8 RDS(ON) = 0.01 Vishay-Siliconix Table 7. Sense Resistor Selection Guide CURRENT LIMIT VALUE PART NUMBER DESCRIPTION MANUFACTURER 1A LR120601R055F WSL1206R055 0.055, 0.5W, 1% Resistor IRC-TT Vishay-Dale 2A LR120601R028F WSL1206R028 0.028, 0.5W, 1% Resistor IRC-TT Vishay-Dale 5A LR120601R011F WSL2010R011 0.011, 0.5W, 1% Resistor IRC-TT Vishay-Dale 7.6A WSL2512R007 0.007, 1W, 1% Resistor Vishay-Dale 10A WSL2512R005 0.005, 1W, 1% Resistor Vishay-Dale 1646fa 18 LTC1646 U W U U APPLICATIO S I FOR ATIO Table 8. Manufacturers' Web Site MANUFACTURER WEB SITE International Rectifier www.irf.com ON Semiconductor www.onsemi.com IRC-TT www.irctt.com Vishay-Dale www.vishay.com Vishay-Siliconix www.vishay.com Diodes, Inc. www.diodes.com U PACKAGE DESCRIPTIO GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 - .196* (4.801 - 4.978) .045 .005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 - .165 .229 - .244 (5.817 - 6.198) .0165 .0015 .150 - .157** (3.810 - 3.988) .0250 BSC RECOMMENDED SOLDER PAD LAYOUT 1 .015 .004 x 45 (0.38 0.10) .007 - .0098 (0.178 - 0.249) 2 3 4 5 6 7 .0532 - .0688 (1.35 - 1.75) 8 .004 - .0098 (0.102 - 0.249) 0 - 8 TYP .016 - .050 (0.406 - 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) .008 - .012 (0.203 - 0.305) TYP .0250 (0.635) BSC GN16 (SSOP) 0204 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 1646fa 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. 19 LTC1646 U TYPICAL APPLICATIO CURRENT FLOW TO LOAD VIN 5V CURRENT FLOW TO LOAD SENSE RESISTOR SO-8 W D G D S D S D S R3 TRACK WIDTH W: 0.03" PER AMPERE ON 1 OZ Cu FOIL VOUT 5V W VIA R5 11 10 9 7 8 12 6 13 14 15 16 C1 5 4 3 2 1 LTC1646* CTIMER CURRENT FLOW TO SOURCE VIA TO GND W GND *ADDITIONAL DETAILS OMITTED FOR CLARITY DRAWING IS NOT TO SCALE! GND 1646 F15 Figure 15. Recommended Layout for Power MOSFET, Sense Resistor, and Gate Components RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1421 Hot Swap Controller Dual Supplies from 3V to 12V, Additionally -12V LTC1422 Hot Swap Controller Single Supply Hot Swap in SO-8 from 3V to 12V LT1640AL/LT1640AH Negative Voltage Hot Swap Controllers in SO-8 Negative High Voltage Supplies from -10V to - 80V LT1641/LT1641-1 Positive Voltage Hot Swap Controller in SO-8 Supplies from 9V to 80V, Autoretry/Latches Off LTC1642 Fault Protected Hot Swap Controller 3V to 15V, Overvoltage Protection Up to 33V LTC1643L/LTC1643L-1/LTC1643H PCI Bus Hot Swap Controllers 3.3V, 5V, 12V, -12V Supplies for PCI Bus LTC1644 CompactPCI Hot Swap Controller 3.3V, 5V, 12V Local Reset Logic and Precharge LTC1645 2-Channel Hot Swap Controller Operates from 1.2V to 12V, Power Sequencing LTC1647 Dual Hot Swap Controller Dual ON Pins for Supplies from 3V to 15V LTC4211 Hot Swap Controller with Multifunction Current Control Single Supply, 2.5V to 16.5V, MSOP 1646fa 20 Linear Technology Corporation LT 1205 REV A * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2000