1646

LTC1646 CompactPCI Dual Hot Swap Controller DESCRIPTIO The LTC®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. The LTC1646 is available in the 16-pin narrow SSOP package. 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 APPLICATIO S ■ CompactPCI Bus Removable Boards , 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. TYPICAL APPLICATIO COMPACT PCI BACKPLANE CONNECTOR (MALE) 5V LONG 5V 3.3V LONG 3.3V COMPACT PCI CIRCUIT CARD CONNECTOR (FEMALE) 2.7Ω Z1 Z2 R2 0.007Ω 1% R1 0.005Ω, 1% Q2 IRF7413 Q1 IRF7413 1.8Ω V(I/O) 0.1µF 0.1µF R3 10Ω 8 3VIN 9 10 7 3VSENSE GATE 3VOUT 12 5VIN 11 5VSENSE 1.2k BD_SEL# V(I/O) 3k HEALTHY# PCI_RST# 3k 1k 15 3 4 16 OFF/ON FAULT LTC1646 PWRGD RESETIN GND 6 PRECHARGE 13 18Ω 4.7nF 18Ω DRIVE 14 1k 12Ω LOCAL_PCI_RST# GROUND 10k I/O PIN 1 DATA BUS Z1, Z2: BZX84C6V2 10Ω PRECHARGE OUT 1V ± 10% IOUT = ± 55mA MMBT2222A 3VIN DATA LINE EXAMPLE DATA BUS Figure 1 U U U 5V 5A 3.3V 7.6A R4 10Ω 5 5VOUT TIMER 2 R5 1k, 5% C1 0.01µF 10k 0.1µF 3VOUT 3k RESETOUT 1 3VIN 3.3V RESET# I/O 5VIN 5V PCI BRIDGE (21154) 1646 F01 1646fa 1 LTC1646 ABSOLUTE (Note 1) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW RESETOUT 1 TIMER 2 FAULT 3 PWRGD 4 5VOUT 5 GND 6 3VOUT 7 3VIN 8 16 RESETIN 15 OFF/ON 14 DRIVE 13 PRECHARGE 12 5VIN 11 5VSENSE 10 GATE 9 3VSENSE 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 ............................................... 0°C to 70°C LTC1646I .............................................–40°C to 85°C Storage Temperature Range ..................–65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C GN PACKAGE 16-LEAD PLASTIC SSOP TJMAX = 125°C, θJA = 135°C/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. The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V5VIN = 5V and V3VIN = 3.3V unless otherwise noted. SYMBOL IDD VLKO VFB PARAMETER V5VIN Supply Current Undervoltage Lockout Foldback Current Limit Voltage CONDITIONS OFF/ON = 0V 5VIN 3VIN 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 = (V5VIN – V5VSENSE), V5VOUT = 5V, TIMER Open VCB = (V3VIN – V3VSENSE), V3VOUT = 3.3V, TIMER Open (V5VIN – V5VSENSE) = 100mV, TIMER Open (V3VIN – V3VSENSE) = 100mV, TIMER Open (V5VIN – V5VSENSE) = 200mV, TIMER Open (V3VIN – V3VSENSE) = 200mV, TIMER Open OFF/ON = 0V, VGATE = 0V, TIMER = 0V OFF/ON = 5V, VGATE = 5V, TIMER = 0V OFF/ON = 0V, VGATE = 5V, FAULT = 0V, TIMER Open OFF/ON = 0V, IGATE = – 1µA OFF/ON = 0V, V5VIN = 3.3V, IGATE = – 1µA 3VOUT 5VOUT ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ELECTRICAL CHARACTERISTICS MIN 2.3 2.3 15 50 15 50 50 50 10 10 TYP 1.5 2.50 2.55 20 55 20 55 56 56 21 21 0.145 0.145 MAX 4 2.7 2.7 30 65 30 65 65 65 30 30 1 1 –8 300 12 16 15 3.0 4.75 200 0.8 UNITS mA V V mV mV mV mV mV mV µs µs µs µs µA µA mA V V V V mV V 1646fa VCB t OC t SS ICP Circuit Breaker Trip Voltage Overcurrent Fault Response Time Short-Circuit Fault Response Time GATE Pin Output Current –18 80 4 12 11 2.8 4.5 50 –13 200 7 15 13 2.9 4.65 120 VGATE VTH V3VONLY VIL External Gate Voltage (GATE to GND) Power Good Threshold Voltage No 5V Input Mode Window Voltage V3VONLY = ⎪V5VIN – V3VIN⎪, V5VOUT = V3VOUT = 3.3V Input Low Voltage OFF/ON, RESETIN, FAULT 2 U W U U WW W LTC1646 The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V5VIN = 5V and V3VIN = 3.3V unless otherwise noted. SYMBOL VIH VTIMER IIN PARAMETER Input High Voltage TIMER Threshold Voltage OFF/ON Input Current RESETIN Input Current 5VSENSE Input Current 3VSENSE Input Current 3VIN Input Current 5VOUT Input Current 3VOUT Input Current ITIMER RDIS VOL VPXG TIMER Pin Current 5VOUT Discharge Impedance 3VOUT Discharge Impedance Output Low Voltage PRECHARGE Reference Voltage CONDITIONS OFF/ON, RESETIN, FAULT VTIMER , FAULT = 0V OFF/ON = 5V OFF/ON = 0V RESETIN = 5V RESETIN = 0V 5VSENSE = 5V, 5VOUT = 0V 3VSENSE = 3.3V, 3VOUT = 0V 3VIN = 3.3V 5VOUT = 5V, OFF/ON = 0V 3VOUT = 3.3V, OFF/ON = 0V OFF/ON = 0V, VTIMER = 0V OFF/ON = 5V, VTIMER = 5V OFF/ON = 5V OFF/ON = 5V FAULT, PWRGD, RESETOUT, I = 2mA VPRECHARGE, V5VIN = 5V and 3.3V ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ELECTRICAL CHARACTERISTICS MIN 2 1.15 TYP 1.25 ±0.08 ±0.08 ±0.08 ±0.08 66 66 460 0.9 0.9 MAX 1.35 ±10 ±10 ±10 ±10 100 100 1000 1.5 1.5 –3 220 220 0.4 1.10 UNITS V V µA µA µA µA µA µA µA mA mA µA mA Ω Ω V V –7 –5 6.6 120 120 0.25 0.90 1.00 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. TYPICAL PERFOR A CE CHARACTERISTICS 5V Current Foldback Profile 12 11 10 9 8 7 6 5 4 3 2 1 0 0 1 RSENSE = 0.007Ω 3 2 4 OUTPUT VOLTAGE (V) 5 1646 G01 8 7 6 5 4 3 2 1 0 0 1 RSENSE = 0.005Ω 3 2 OUTPUT VOLTAGE (V) 4 5 1646 G02 SUPPLY CURRENT (mA) OUTPUT CURRENT (A) OUTPUT CURRENT (A) UW 3.3V Current Foldback Profile 12 11 10 9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 5VIN Supply Current vs Temperature 1.0 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G03 1646fa 3 LTC1646 TYPICAL PERFOR A CE CHARACTERISTICS 5VIN Undervoltage Lockout Voltage vs Temperature 2.60 UNDERVOLTAGE LOCKOUT VOLTAGE (V) UNDERVOLTAGE LOCKOUT VOLTAGE (V) LOW-TO-HIGH TRANSITION FOLDBACK CURRENT LIMIT VOLTAGE (mV) 2.55 LOW-TO-HIGH TRANSITION 2.50 HIGH-TO-LOW TRANSITION 2.45 2.40 –50 –25 0 25 50 TEMPERATURE (°C) 3VIN Foldback Current Limit Voltage vs Temperature 60 FOLDBACK CURRENT LIMIT VOLTAGE (mV) CIRCUIT BREAKER TRIP VOLTAGE (mV) 50 40 30 20 10 0 –50 3VOUT = 0V 3VOUT = 2V 60 59 58 57 56 55 54 53 52 51 CIRCUIT BREAKER TRIP VOLTAGE (mV) –25 0 25 50 TEMPERATURE (°C) 5VIN/3VIN Overcurrent Fault Response Time vs Temperature 21.75 21.50 21.25 21.00 20.75 20.50 20.25 20.00 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G10 SHORT-CIRCUIT FAULT RESPONSE TIME (ns) OVERCURRENT FAULT RESPONSE TIME (µs) 22.00 GATE CURRENT (µA) 4 UW 75 75 3VIN Undervoltage Lockout Voltage vs Temperature 2.60 60 50 40 30 20 10 5VIN Foldback Current Limit Voltage vs Temperature 5VOUT = 4V 2.55 HIGH-TO-LOW TRANSITION 2.50 5VOUT = 0V 2.45 100 1646 G04 2.40 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G05 0 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G06 5VIN Circuit Breaker Trip Voltage vs Temperature 60 59 58 57 56 55 54 53 52 51 3VIN Circuit Breaker Trip Voltage vs Temperature 100 1646 G07 50 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G08 50 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G09 5VIN/3VIN Short-Circuit Fault Response Time vs Temperature 170 160 –11 150 140 130 120 110 100 –50 –10 Gate Current vs Temperature –12 –13 –14 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G11 –15 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G12 1646fa LTC1646 TYPICAL PERFOR A CE CHARACTERISTICS Gate ISINK vs Temperature 10 FAULT = 0V 9 GATE VOLTAGE (V) GATE ISINK (mA) 15.0 14.5 14.0 13.5 5VIN = 3.3V 6 13.0 12.5 –50 15.5 5VIN = 5V POWER GOOD THRESHOLD VOLTAGE (V) 75 100 1646 G14 8 7 5 –50 –25 0 25 50 TEMPERATURE (°C) Power Good Threshold Voltage vs Temperature (5VOUT) 4.75 POWER GOOD THRESHOLD VOLTAGE (V) TIMER THRESHOLD VOLTAGE (V) 1.30 4.70 1.28 5VSENSE INPUT CURRENT (µA) 4.65 4.60 4.55 4.50 –50 –25 0 25 50 TEMPERATURE (°C) 3VSENSE Input Current vs Temperature 70 69 3VSENSE INPUT CURRENT (µA) 3VIN INPUT CURRENT (µA) 68 67 66 65 64 63 62 61 60 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G19 470 465 460 455 450 445 –50 TIMER CURRENT (µA) UW 75 1646 G13 Gate Voltage vs Temperature 3.00 I = –1µA Power Good Threshold Voltage vs Temperature (3VOUT) 2.95 2.90 2.85 100 –25 0 25 50 TEMPERATURE (°C) 2.80 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G15 Timer Threshold Voltage vs Temperature 70 69 68 67 66 65 64 63 62 61 5VSENSE Input Current vs Temperature 1.26 1.24 1.22 75 100 1646 G16 1.20 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G17 60 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G18 3VIN Input Current vs Temperature 480 475 –4.00 –4.25 –4.50 –4.75 –5.00 –5.25 –5.50 –5.75 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G20 Timer Current vs Temperature –6.00 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G21 1646fa 5 LTC1646 TYPICAL PERFOR A CE CHARACTERISTICS RESETOUT, PWRGD and FAULT Output Low Voltage vs ISINK 1.0 0.9 OUTPUT LOW VOLTAGE (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 ISINK (mA) 4 5 1646 G22 3VOUT/5VOUT DISCHARGE IMPEDANCE (Ω) 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 5µA 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 21µs 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 50µs 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. 6 UW 5VOUT/3VOUT Discharge Impedance vs Temperature 180 160 140 120 100 80 60 40 20 0 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1646 G23 90°C 25°C –45°C U U U 1646fa LTC1646 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 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 21µs 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. 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 13µA 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 200µA 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. 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 21µs 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. 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. 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 13µA current source. When the OFF/ON pin is pulled high the GATE pin will be pulled to ground by a 200µA 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. U U U 1646fa 7 LTC1646 TEST DIAGRA TI I G DIAGRA S tOC Overcurrent Fault Detect FALL TIME ≤ 1µs, 5VIN = 5V, 3VIN = 3.3V 5V V5VSENSE OR 3.3V 100mV OR V3VSENSE 8 W W 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 UW 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 LTC1646 BLOCK DIAGRA 5VIN 12 5VSENSE 11 5VOUT +– 55mV + – Q1 +– + 150mV +– – 2.5V UVL OFF/ON 15 FAULT 3 Q7 CP4 PWRGD 4 LOGIC Q6 REF RESETIN 16 5Vin 5µA TIMER 2 Q5 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. U W W GATE 10 VGG 13µA 3VOUT 3VSENSE 9 3VIN 8 3VOUT 5VOUT 7 5 + – –+ 55mV 200µA –+ + 150mV Q2 Q3 – –+ 2.5V UVL CP3 + – + – REF Q4 1 RESETOUT + – 1V 6 GND 14 DRIVE 13 PRECHARGE 1646 BD U U 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 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 21µs, 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 5V 3.3V TOLERANCE 5V ± 5% 3.3V ± 0.3V CAPACITIVE LOAD < 3000µF < 3000µF Power-Up Sequence The LTC1646 is specifically designed for hot swapping CPCI boards. The typical application is shown in Figure 1. 10 U 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 5µA 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 13µA = , or = , or = (1) dt C1 C LOAD(5 VOUT ) C LOAD(3 VOUT ) W U U whichever is slower. 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 LTC1646 APPLICATIO S I FOR ATIO GATE 10V/DIV 5VOUT 3VOUT 5V/DIV TIMER 5V/DIV BD_SEL# 5V/DIV HEALTHY# 5V/DIV LCL_PCI_RST# 5V/DIV PRECHARGE 5V/DIV 20ms/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 200µA 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 5µA current source is connected to the TIMER pin and current limit faults are ignored until the voltage exceeds 1.25V. This feature U GATE 10V/DIV 5VOUT 3VOUT 5V/DIV TIMER 5V/DIV BD_SEL# 5V/DIV HEALTHY# 5V/DIV LCL_PCI_RST# 5V/DIV PRECHARGE 5V/DIV 10ms/DIV 1646 F03 W UU 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) = 2000µF, 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 5µA (3) As a design aid, the timer period as a function of the timing capacitor using standard values from 0.01µF to 1µF is shown in Table 2. 1646fa 11 LTC1646 APPLICATIO S I FOR ATIO Table 2. t TIMER vs CTIMER CTIMER 0.01µF 0.022µF 0.033µF 0.047µF 0.068µF 0.082µF 0.1µF tTIMER 2.5ms 5.5ms 8.25ms 11.8ms 17ms 20.5ms 25ms CTIMER 0.22µF 0.33µF 0.47µF 0.68µF 0.82µF 1µF 82.5ms 118ms 170ms 205ms 250ms The TIMER pin is immediately pulled low when BD_SEL# goes high. 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 5VOUT 3VOUT 2V/DIV TIMER 1V/DIV BD_SEL# 5V/DIV LCL_PCI_RST# 5V/DIV HEALTHY# 5V/DIV FAULT 5V/DIV 10ms/DIV Figure 4. Power-Up into a Short on 3.3V Output 12 U tTIMER 55ms W UU 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 21µs, the circuit breaker trips and both supplies are turned off (Figure 5). 5VIN – 5VSENSE 50mV/DIV GATE 10V/DIV FAULT 5V/DIV 10µs/DIV 1646 F05 Figure 5. Overcurrent Fault on 5V 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. 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 LTC1646 APPLICATIO S I FOR ATIO 5VIN –5VSENSE 100mV/DIV GATE 10V/DIV FAULT 5V/DIV 5µs/DIV Figure 6. Short-Circuit Fault on 5V 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) = 55mV RSENSE(XVOUT) 20mV RSENSE(XVOUT) (5) (4) IFOLDBACK(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 (Ω) 0.005 0.006 0.007 0.008 0.009 0.01 ILIMIT(XVOUT) 11A 9.2A 7.9A 6.9A 6.1A 5.5A IFOLDBACK(XVOUT) 4A 3.3A 2.9A 2.5A 2.2A 2A where XVOUT = 3VOUT or 5VOUT. U 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. ILOAD(MAX) 5VIN 1 3 12 5VIN RSENSE 2 4 11 5VSENSE W UU + – – 1646 F06 VCB LTC1646* + VCB(MAX) = 65mV VCB(NOM) = 56mV VCB(MIN) = 50mV *ADDITIONAL DETAILS OMITTED FOR CLARITY 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 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 ⎠ 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 = 0.0074Ω 6.8A The nominal sense resistor value is (Equation 7): RSENSE(NOM) = RSENSE(MAX) 0.0074Ω = = 0.007Ω ⎛ RTOL⎞ ⎛5⎞ 1+ ⎜ ⎟ 1+ ⎜ ⎟ ⎝ 100 ⎠ ⎝ 100⎠ And the new current-limit trip point is Equation 8: 14 U ITRIP(MAX,NEW) = VCB(MAX) = RSENSE(MIN) W UU (7) 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# LO LO HI HI HEALTHY# LO HI LO HI LOCAL_PCI_RST# LO LO HI LO If either of the output voltages drop below the power good threshold for more than 50µs, 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 LTC1646 APPLICATIO S I FOR ATIO VPRECHARGE 1.5V 1.4V 1.3V 1.2V 1.1V 1V R1 18Ω 18Ω 18Ω 18Ω 18Ω 18Ω R2 9.09Ω 7.15Ω 5.36Ω 3.65Ω 1.78Ω 0Ω VPRECHARGE 0.9V 0.8V 0.7V 0.6V 0.5V R1 Table 5. R1 and R2 Resistor Values vs Precharge Voltage R2 1.78Ω 3.65Ω 5.11Ω 7.15Ω 9.09Ω 16.2Ω 14.7Ω 12.1Ω 11Ω 9.09Ω LTC1646* GND 6 4.7nF R1 PRECHARGE DRIVE 13 14 18Ω 1k 12Ω R2 MMBT2222A 3VIN R1 GND 6 PRECHARGE OUT R1 VPRECHARGE = • 1V R1 + R2 *ADDITIONAL DETAILS OMITTED FOR CLARITY 1646 F08 Figure 8. Precharge Voltage 1V Application Circuit 0.005Ω 1 1% 2 3 4 IRF7413 3.3VOUT 7.6A 10Ω 1k 0.010µF 10k 0.1µF 3VOUT 3k 3VIN 3.3V RESET# PRECHARGE OUT 1V ±10% IOUT = ± 55mA 3VIN I/O DATA LINE EXAMPLE DATA BUS PCI BRIDGE (21154) 1646 F10 15 LTC1646 APPLICATIO S I FOR ATIO COMPACT PCI COMPACT PCI BACKPLANE CIRCUIT CARD CONNECTOR CONNECTOR (MALE) (FEMALE) 5VIN 5V LONG 5V 2.7Ω GND Z1: BZX84C6V2 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) BD_SEL# 100Ω LONG GND 1k LTC1646 6 GND 1646 F12 1.2k 15 OFF/ON Figure 12. BD_SEL# Pushbutton Toggle Switch 16 U Z1 1 3 0.007Ω 2 IRF7413 4 10Ω 1k 0.1µF 8 9 12 11 10 5 7 3VIN 3VSENSE 5VIN 5VSENSE GATE 5VOUT 3VOUT 6 GND LTC1646 0.01µF 5VOUT BAV16W 1646 F11 W UU 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. 1646fa LTC1646 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. 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 10× to 100× 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 1Ω to 10Ω. Note that in all 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 GND 3VIN 1646 F14 *ADDITIONAL DETAILS OMITTED FOR CLARITY DRAWING IS NOT TO SCALE! Figure 14. Recommended Layout for Transient Protection Components R2 0.007Ω Q1 IRF7413 VIN1 5V LONG 5V VIN2 3.3V LONG 3.3V 8 R6 2.7Ω R1 0.005Ω R7 1.8Ω R3 10Ω R4 10Ω R5 1k C1 0.01µF 8 3VIN Z1 C2 0.1µF 3VSENSE GATE Z1, Z2: BZX84C6V2 **ADDITIONAL DETAILS OMITTED FOR CLARITY Figure 13. Place Transient Protection Device Close to the LTC1646 U 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. 5VIN TZ1 LTC1646* TZ2 C3 C2 VIAS TO GND PLANE 5VOUT AT 5A 3VOUT AT 7.6A Q2 IRF7413 9 10 7 3VOUT GND 5VIN 12 11 5VSENSE 5 5VOUT Z2 C3 0.1µF 1646 F13 W UU LTC1646** 6 1646fa 17 LTC1646 APPLICATIO S I FOR ATIO 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 approximately 0.5mΩ/■ , track resistances add up quickly 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. Table 6. N-Channel Power MOSFET Selection Guide CURRENT LEVEL (A) 0 to 2 2 to 5 5 to 10 5 to 10 5 to 10 PART NUMBER MMDF3N02HD MMSF5N02HD MTB50N06V IRF7413 Si4410DY Table 7. Sense Resistor Selection Guide CURRENT LIMIT VALUE 1A 2A 5A 7.6A 10A PART NUMBER LR120601R055F WSL1206R055 LR120601R028F WSL1206R028 LR120601R011F WSL2010R011 WSL2512R007 WSL2512R005 DESCRIPTION 0.055Ω, 0.5W, 1% Resistor 0.028Ω, 0.5W, 1% Resistor 0.011Ω, 0.5W, 1% Resistor 0.007Ω, 1W, 1% Resistor 0.005Ω, 1W, 1% Resistor MANUFACTURER IRC-TT Vishay-Dale IRC-TT Vishay-Dale IRC-TT Vishay-Dale Vishay-Dale Vishay-Dale 18 U 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. 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. DESCRIPTION Dual N-Channel SO-8 RDS(ON) = 0.1Ω Single N-Channel SO-8 RDS(ON) = 0.025Ω Single N-Channel DD Pak RDS(ON) = 0.028Ω Single N-Channel SO-8 RDS(ON) = 0.01Ω Single N-Channel SO-8 RDS(ON) = 0.01Ω MANUFACTURER ON Semiconductor ON Semiconductor ON Semiconductor International Rectifier Vishay-Siliconix 1646fa W U U LTC1646 APPLICATIO S I FOR ATIO Table 8. Manufacturers’ Web Site MANUFACTURER International Rectifier ON Semiconductor IRC-TT Vishay-Dale Vishay-Siliconix Diodes, Inc. WEB SITE www.irf.com www.onsemi.com www.irctt.com www.vishay.com www.vishay.com www.diodes.com PACKAGE DESCRIPTIO GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .045 ± .005 .254 MIN .150 – .165 .0165 ± .0015 .0250 BSC RECOMMENDED SOLDER PAD LAYOUT .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) 0° – 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U .189 – .196* (4.801 – 4.978) 16 15 14 13 12 11 10 9 .009 (0.229) REF U W U U .229 – .244 (5.817 – 6.198) .150 – .157** (3.810 – 3.988) 1 .0532 – .0688 (1.35 – 1.75) 23 4 56 7 8 .004 – .0098 (0.102 – 0.249) .008 – .012 (0.203 – 0.305) TYP .0250 (0.635) BSC GN16 (SSOP) 0204 1646fa 19 LTC1646 TYPICAL APPLICATIO U SENSE RESISTOR D VIN 5V D W D D CURRENT FLOW TO LOAD SO-8 G S S S W VOUT 5V R3 R5 C1 16 15 14 13 12 11 10 9 CURRENT FLOW TO LOAD TRACK WIDTH W: 0.03" PER AMPERE ON 1 OZ Cu FOIL VIA LTC1646* 1 2 3 4 5 6 7 8 CTIMER CURRENT FLOW TO SOURCE VIA TO GND GND W GND *ADDITIONAL DETAILS OMITTED FOR CLARITY DRAWING IS NOT TO SCALE! 1646 F15 Figure 15. Recommended Layout for Power MOSFET, Sense Resistor, and Gate Components RELATED PARTS PART NUMBER LTC1421 LTC1422 LT1640AL/LT1640AH LT1641/LT1641-1 LTC1642 LTC1643L/LTC1643L-1/LTC1643H LTC1644 LTC1645 LTC1647 LTC4211 DESCRIPTION Hot Swap Controller Hot Swap Controller Negative Voltage Hot Swap Controllers in SO-8 Positive Voltage Hot Swap Controller in SO-8 Fault Protected Hot Swap Controller PCI Bus Hot Swap Controllers CompactPCI Hot Swap Controller 2-Channel Hot Swap Controller Dual Hot Swap Controller Hot Swap Controller with Multifunction Current Control COMMENTS Dual Supplies from 3V to 12V, Additionally –12V Single Supply Hot Swap in SO-8 from 3V to 12V Negative High Voltage Supplies from –10V to – 80V Supplies from 9V to 80V, Autoretry/Latches Off 3V to 15V, Overvoltage Protection Up to 33V 3.3V, 5V, 12V, –12V Supplies for PCI Bus 3.3V, 5V, ± 12V Local Reset Logic and Precharge Operates from 1.2V to 12V, Power Sequencing Dual ON Pins for Supplies from 3V to 15V Single Supply, 2.5V to 16.5V, MSOP 1646fa LT 1205 REV A • PRINTED IN USA 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2000