LTC4223-1/LTC4223-2 Dual Supply Hot Swap Controller for Advanced Mezzanine Card DESCRIPTION FEATURES Allows Safe Insertion into Live AMC or MicroTCA Backplane Controls 12V Main and 3.3V Auxiliary Supplies Limits Peak Fault Current in 1s Adjustable Current Limit with Circuit Breaker Integrated 0.3 AUX Switch High Side Current Sense Gate Drive for External N-Channel MOSFET Adjustable Response Time for Overcurrent Protection Adjustable Supply Voltage Power-Up Rate Thermal Shutdown Protection LTC4223-1: Latch Off After Fault LTC4223-2: Automatic Retry After Fault 16-Lead SSOP and 5mm x 4mm DFN Packages APPLICATIONS Advanced Mezzanine Card, MicroTCA Systems Workstations and Server I/O Telecom Networks The LTC(R)4223 positive voltage Hot SwapTM controller allows a board to be safely inserted and removed from a live AMC or MicroTCA backplane. It controls the main 12V supply with an external N-channel MOSFET and the 3.3V auxiliary supply with an integrated switch. The 12V output ramp rate is adjustable and includes inrush current limiting. The 12V output is also protected against short circuit faults with a fast acting current limit and a 5% accurate timed circuit breaker. The 3.3V output includes both soft start and overcurrent protection. The LTC4223 features a current monitor output for the 12V supply, and reports fault and power-good status for both supplies. It also detects card presence and allows independent control of the 12V and auxiliary 3.3V supply outputs. The LTC4223-1 features a latch-off circuit breaker, while the LTC4223-2 provides automatic retry after a fault. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Advanced Mezzanine Card Application 6m Si7336ADP 12V 7.4A 12V 10 12VIN 3.3V Normal Power-Up Waveform 47 15nF 12VSENSE 12VGATE 12VOUT 5V/DIV 12VOUT AUXIN AUXOUT 3.3V 150mA AUXPGOOD 5V/DIV 12PGOOD 5V/DIV 51 VCC 330nF AUXON 12ON AUXPGOOD 12PGOOD FAULT IPMC ADC EN 5V/DIV AUXOUT 5V/DIV LTC4223-1/LTC4223-2 20ms/DIV 12IMON 422312 TA01b EN GND TIMER 0.1F 422312 TA01a CARRIER MODULE CONNECTOR CONNECTOR 422312f 1 LTC4223-1/LTC4223-2 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltages 12VIN ..................................................... -0.3V to 20V AUXIN .................................................... -0.3V to 10V VCC........................................................... -0.3V to 7V Input Voltages 12ON, AUXON, EN ................................... -0.3V to 7V TIMER..........................................-0.3V to VCC + 0.3V 12VSENSE ............................................... -0.3V to 20V Output Voltages FAULT, 12PGOOD, AUXPGOOD, 12IMON ................................................... -0.3V to 7V 12VGATE ................................................. -0.3V to 25V 12VOUT - 12VGATE (Note 3) ................... -4.5V to 0.3V AUXOUT................................................. -0.3V to 10V Operating Temperature Range LTC4223-1C/ LTC4223-2C ....................... 0C to 70C LTC4223-1I/ LTC4223-2I ..................... -40C to 85C Storage Temperature Range GN Package ....................................... -65C to 150C DHD Package ..................................... -65C to 125C Lead Temperature (Soldering, 10sec) GN Package ...................................................... 300C PIN CONFIGURATION TOP VIEW TOP VIEW 12VSENSE 1 16 12VGATE 12VIN 2 15 12VOUT 12IMON 3 14 12PGOOD 12ON 4 13 FAULT AUXIN 5 12 AUXOUT VCC 6 11 AUXPGOOD AUXON 7 10 EN GND 8 9 12VSENSE 1 16 12VGATE 12VIN 2 15 12VOUT 12IMON 3 14 12PGOOD 12ON 4 AUXIN 5 12 AUXOUT VCC 6 11 AUXPGOOD AUXON 7 10 EN GND 8 9 17 13 FAULT TIMER TIMER DHD PACKAGE 16-LEAD (5mm x 4mm) PLASTIC DFN GN PACKAGE 16-LEAD PLASTIC SSOP EXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONAL MUST BE SOLDERED TO PCB TO OBTAIN JA = 43C/W, OTHERWISE JA = 140C/W, TJMAX = 125C TJMAX = 125C, JA = 110C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4223CDHD-1#PBF LTC4223CDHD-1#TRPBF 42231 16-Lead (5mm x 4mm) Plastic DFN 0C to 70C LTC4223CDHD-2#PBF LTC4223CDHD-2#TRPBF 42232 16-Lead (5mm x 4mm) Plastic DFN 0C to 70C LTC4223IDHD-1#PBF LTC4223IDHD-1#TRPBF 42231 16-Lead (5mm x 4mm) Plastic DFN -40C to 85C LTC4223IDHD-2#PBF LTC4223IDHD-2#TRPBF 42232 16-Lead (5mm x 4mm) Plastic DFN -40C to 85C LTC4223CGN-1#PBF LTC4223CGN-1#TRPBF 42231 16-Lead Plastic SSOP 0C to 70C LTC4223CGN-2#PBF LTC4223CGN-2#TRPBF 42232 16-Lead Plastic SSOP 0C to 70C LTC4223IGN-1#PBF LTC4223IGN-1#TRPBF 4223I1 16-Lead Plastic SSOP -40C to 85C LTC4223IGN-2#PBF LTC4223IGN-2#TRPBF 4223I2 16-Lead Plastic SSOP -40C to 85C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 422312f 2 LTC4223-1/LTC4223-2 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. (Note 2) SYMBOL PARAMETER CONDITIONS MIN VDD Input Supply Range VCC AUXIN 12VIN IDD Input Supply Current VCC AUXIN 12VIN VDD(UVLO) Input Supply Undervoltage Lockout VCC Rising VAUXIN Rising V12VIN Rising VDD(UVLO, HYST) Input Supply Undervoltage Lockout Hysteresis VCC AUXIN 12VIN TYP MAX UNITS Supplies 2.7 2.7 10 6 6 14 V V V 0.8 0.4 0.6 2 1 1 mA mA mA 2.3 2.4 9.4 2.45 2.5 9.7 2.6 2.6 10 V V V 40 70 70 110 110 110 180 150 150 mV mV mV Circuit Breaker Trip Sense Voltage, (V12VIN - V12VSENSE) 47.5 50 52.5 mV VSENSE(ACL) Active Current Limit Sense Voltage, (V12VIN - V12VSENSE) 54 60 66 mV IAUX(ACL) AUXOUT Active Current Limit VAUXOUT = 0V 165 240 330 mA Switch Resistance (VAUXIN - VAUXOUT)/IAUXOUT IAUXOUT = 150mA (Note 4) 0.3 0.5 VGATE External N-Channel Gate Drive (V12VGATE - V12VOUT) (Note 3) 4.5 6.2 7.9 V IGATE(UP) External N-Channel Gate Pull-Up Current Gate Drive On, V12VGATE = 0V -7 -10 -14 A 0.5 1 2 mA Current Limit VSENSE(CB) Integrated Switch RDS(ON) Gate Drive IGATE(DN) External N-Channel Gate Pull-Down Current Gate Drive Off V12VGATE = 17V, V12VOUT = 12V IGATE(FPD) External N-Channel Gate Fast Pull-Down Current Fast Turn Off V12VGATE = 17V, V12VOUT = 12V 90 160 250 mA G12IMON 12IMON Pin Gain Ratio V12IMON/(V12VIN - V12VSENSE) (V12VIN - V12VSENSE) = (75mV, 25mV) 30 33 36 V/V V12IMON 12IMON Pin Output Voltage (V12VIN - V12VSENSE) = 75mV, VCC = 2.7V 2.25 2.475 2.7 V 82.5 Current Sense VSENSE(MAX) 12IMON Pin Maximum Input Sense Voltage V12IMON(CLP) 12IMON Pin Clamp Voltage (V12VIN - V12VSENSE) = 150mV, VCC = 2.7V 2.9 3.2 3.5 mV V R12IMON 12IMON Pin Output Resistance (V12VIN - V12VSENSE) = 0V 115 165 215 k V12IMON(MIN) 12IMON Pin Minimum Output Voltage (V12VIN - V12VSENSE) = 0V 0 130 mV Comparator Inputs VPG(TH) Power Good Threshold Voltage V12VOUT Falling VAUXOUT Falling 10 2.8 10.3 2.885 10.6 2.97 V V VPG(HYST) Power Good Hysteresis V12VOUT VAUXOUT 20 5 60 16 110 30 mV mV VTMR(TH) TIMER Pin Threshold Voltage VTIMER Rising VTIMER Falling 1.198 0.15 1.235 0.2 1.272 0.25 V V 422312f 3 LTC4223-1/LTC4223-2 ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS ITMR(UP) TIMER Pull-Up Current VTIMER = 1V, Initial Timing Cycle VTIMER = 0V, In AUX Fault Mode VTIMER = 0V, In 12V Fault Mode -7 -7 -140 -10 -10 -200 -13 -13 -260 A A A ITMR(DN) TIMER Pull-Down Current VTIMER = 2V, No Faults VTIMER = 2V, In Reset Mode 1.3 2 2 8 2.6 16 A mA IOL = 3mA 0.15 0.4 V (Note 5) VCC - 1 VPU = 1.5V -6 0.8 Open Drain Outputs VOL VOH IPU Output Low Voltage (FAULT, 12PGOOD, AUXPGOOD) U L T , 1 2 P G O O D , Output High Voltage (F A AUXPGOOD) U L T , Output Pin Pull-Up Current (F A 12PGOOD, AUXPGOOD) V -10 -14 A 2 V 1 A Logic Inputs VIN(TH) Logic Input Threshold (12ON, AUXON, EN) IIN(LEAK) Input Leakage Current (12ON, AUXON) RPU EN Pin Pull-Up Resistance VIN = VCC 60 100 140 k Other Pin Functions I12VSENSE 12VSENSE Pin Input Current V12VSENSE = 12V 10 50 100 A I12VOUT 12VOUT Pin Input Current Gate Drive On, V12VOUT = 12V 20 50 100 A ROUT(DIS) OUT Pin Discharge Resistance 12VOUT AUXOUT Gate Drive Off V12VOUT = 6V VAUXVOUT = 2V 400 375 800 750 1600 1500 12 Propagation Delays tCB AUX Circuit Breaker Trip Delay After Power Up 25 50 s tPHL(SENSE) Sense Voltage, (12VIN - 12VSENSE) High to 12VGATE Low VSENSE = 300mV, C12VGATE = 10nF VSENSE = 100mV, C12VGATE = 10nF 0.5 5 1 12 s s tPHH(AUXON) AUXON High to AUXOUT High 15 30 s tPHH(12ON) 12ON High to 12VGATE High 30 60 s tRST(ON) Input Low (12ON, AUXON) to FAULT High 20 40 s tRST(VCC) VCC Low to FAULT High 80 150 s tPLL(UVLO) 12VIN Low to 12VGATE Low 6 12 18 s AUXIN Low to AUXPGOOD High 6 12 18 s tPHL(GATE) EN High to 12VGATE Low 20 40 s tPLH(PG) 12VOUT Low to 12PGOOD High 20 40 s AUXOUT Low to AUXPGOOD High 20 40 s 2 6 s tP(12IMON) Input Sense Voltage Step to 12IMON Propagation Delay VSENSE = 100mV Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into device pins are positive; all currents out of the device pins are negative. All voltages are referenced to GND unless otherwise specified. Note 3: An internal clamp limits the 12VGATE pin to a minimum of 4.5V above 12VOUT. Driving this pin to voltages beyond the clamp may damage the device. Note 4: For the DFN package, the AUX switch on resistance, RDS(ON) limit is guaranteed by correlation to wafer test measurements. U L T , 1 2 P G O O D and A U X P G O O D have an internal Note 5: The output pins F A pull-up to VCC of 10A. However, an external pull-up resistor may be used when faster rise time is required or for VOH voltages greater than VCC. 422312f 4 LTC4223-1/LTC4223-2 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are TA = 25C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. ICC vs VCC 1.0 SUPPLY CURRENT (mA) 1.2 0.8 0.4 35 0.8 VCC 0.6 12VIN 12IMON GAIN RATIO (V/V) 1.6 ICC (mA) 12IMON Gain Ratio vs Temperature Supply Current vs Temperature AUXIN 0.4 34 33 32 0.2 0 - 50 0 2.5 3.0 3.5 4.0 4.5 VCC (V) 5.0 5.5 6.0 - 25 0 25 50 TEMPERATURE (C) AUXOUT POWER-GOOD THRESHOLD (V) 12VOUT POWER-GOOD THRESHOLD (V) RISING FALLING 10.2 10.1 1 10.0 -50 0 0 20 40 60 80 100 SENSE VOLTAGE (mV) 120 140 -25 0 25 50 TEMPERATURE (C) Circuit Breaker Trip Voltage vs Temperature 49 -25 0 25 50 TEMPERATURE (C) 75 100 422312 G07 RISING FALLING 2.86 2.84 -50 100 -25 0 25 50 TEMPERATURE (C) 75 AUX Active Current Limit vs Temperature 250 62 61 60 59 58 -50 100 422312 G06 AUX ACTIVE CURRENT LIMIT (mA) ACTIVE CURRENT LIMIT SENSE VOLTAGE (mV) 50 100 2.88 Active Current Limit Sense Voltage vs Temperature 51 48 -50 75 2.90 422312 G05 422312 G04 52 70 2.92 10.3 2 0 25 50 TEMPERATURE (C) AUXOUT Power-Good Threshold vs Temperature 10.4 4 3 -25 422312 G03 12VOUT Power-Good Threshold vs Temperature 12IMON Output Voltage vs Sense Voltage 12IMON OUTPUT VOLTAGE (V) 31 -50 100 422312 G02 422312 G01 CIRCUIT BREAKER TRIP VOLTAGE (mV) 75 -25 0 25 50 TEMPERATURE (C) 75 100 422312 G08 240 230 220 210 200 - 50 - 25 0 25 50 TEMPERATURE (C) 75 100 422312 G09 422312f 5 LTC4223-1/LTC4223-2 TYPICAL PERFORMANCE CHARACTERISTICS Specifications are TA = 25C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specified. AUX Switch On Resistance vs Temperature Gate Drive vs Temperature 0.3 0.2 GATE DRIVE (VGATE) (V) 6 0.4 6.2 6.1 6.0 -25 0 25 50 TEMPERATURE (C) 75 5.9 -50 100 4 3 2 0 -25 0 25 50 TEMPERATURE (C) 422312 G10 75 0 100 -25 0 25 50 TEMPERATURE (C) 75 25 20 15 - 50 100 0 25 50 TEMPERATURE (C) 422312 G13 75 100 OUTPUT DISCHARGE RESISTANCE () 200 150 100 0 25 50 TEMPERATURE (C) 75 0.1 50 100 422312 G16 100 150 200 250 SENSE VOLTAGE (mV) Logic Input Threshold vs VCC 3.0 1000 12VOUT 800 AUXOUT 600 400 200 - 50 300 422312 G15 1200 -25 1 Output Discharge Resistance vs Temperature 250 50 -50 10 422312 G14 Gate Fast Pull-Down Current vs Temperature -12 0.01 - 25 LOGIC INPUT THRESHOLD (V) -9.0 -50 -10 100 ACTIVE CURRENT LIMIT DELAY (s) AUX CIRCUIT BREAKER TRIP DELAY (s) -9.5 -8 -6 IGATE (A) Active Current Limit Delay vs Sense Voltage 30 -11.0 -10.0 -4 422312 G12 AUX Circuit Breaker Trip Delay vs Temperature -10.5 -2 422312 G11 Gate Pull-Up Current vs Temperature GATE PULL-UP CURRENT (A) 5 1 0.1 -50 GATE FAST PULL-DOWN CURRENT (mA) Gate Drive vs IGATE 7 6.3 GATE DRIVE (VGATE) (V) AUX SWITCH-ON RESISTANCE () 0.5 - 25 0 25 50 TEMPERATURE (C) 75 100 422312 G17 2.5 HIGH 2.0 LOW 1.5 1.0 0.5 0 2.5 3.0 3.5 4.0 4.5 VCC (V) 5.0 5.5 6.0 422312 G18 422312f 6 LTC4223-1/LTC4223-2 PIN FUNCTIONS 12VSENSE (Pin 1): 12V Current Sense Input. Connect this pin to the output of the current sense resistor. The electronic circuit breaker trips if the voltage across the sense resistor exceeds 50mV for more than a fault filter delay. 12VIN (Pin 2): 12V Supply Input. Undervoltage lockout disables the 12V supply until the input at 12VIN exceeds 9.7V. 12IMON (Pin 3): 12V Current Sense Monitoring Output. This pin monitors the sense voltage between 12VIN and 12VSENSE. The gain ratio between this pin's voltage and the sense voltage is 33. 12ON (Pin 4): 12V Supply On Control Digital Input. A rising edge turns on the external N-channel MOSFET if EN is pulled low and a falling edge turns it off. A high-to-low transition on this pin will clear the 12V supply faults. AUXIN (Pin 5): Auxiliary Supply Input. An internal 0.3 switch is connected between AUXIN and AUXOUT pins. Undervoltage lockout holds the switch off until the input at AUXIN exceeds 2.5V. VCC (Pin 6): Bias Supply Input. This pin provides power to the device's internal circuitry and operates from 2.7V to 6V. Undervoltage lockout circuit disables the device until the input at VCC exceeds 2.45V. Bypass with 330nF. AUXON (Pin 7): Auxiliary Supply On Control Digital Input. A rising edge turns on the internal switch if EN is pulled low and a falling edge turns it off. A high-to-low transition on both this pin and 12ON pin will clear the auxiliary supply faults. GND (Pin 8): Device Ground. TIMER (Pin 9): Timer Capacitor Terminal. Connect a capacitor between this pin and ground to set a 741ms/F duration for initial timing cycle, 123ms/F for AUX current limit during power-up and 6ms/F duration for 12V current limit before the external MOSFET is turned off. EN (Pin 10): Enable Input Intended for Card Presence Detect. Ground this pin to enable the external N-channel MOSFET and internal switch to turn on. If this pin is pulled high, the switches are not allowed to turn on. An internal 100k resistor pulls up this pin. A high-to-low transition will clear faults. AUXPGOOD (Pin 11): Auxiliary Supply Power Status Output. Open drain output that is normally pulled high by an internal 10A current source or an external pull-up resistor to VCC. It pulls low when the AUXOUT pin voltage exceeds the power-good threshold of 2.901V. AUXOUT (Pin 12): Auxiliary Supply Output. This pin is the output from the internal switch connected between AUXIN and AUXOUT pins. It signals AUXPGOOD low when it exceeds 2.901V. A 750 active pull-down discharges AUXOUT to ground when the internal switch is turned off. FAULT (Pin 13): Auxiliary and 12V Supply Fault Status Output. Open drain output that is normally pulled high by an internal 10A current source or an external pull-up resistor to VCC. It pulls low when the circuit breaker is tripped due to an overcurrent fault on auxiliary or 12V supply. 1 2PGOOD (Pin 14): 12V Supply Power Status Output. Open drain output that is normally pulled high by an internal 10A current source or an external pull-up resistor to VCC. It pulls low when the 12VOUT pin voltage exceeds the power-good threshold of 10.36V. 12VOUT (Pin 15): 12V Gate Drive Return and Power-Good Input. Connect this pin to the source of the external Nchannel MOSFET for gate drive return. This pin signals 12PGOOD low when it exceeds 10.36V. When the external MOSFET is turned off, 12VOUT is discharged to ground through a 800 active pull-down. 12VGATE (Pin 16): Gate Drive for 12V Supply External NChannel MOSFET. An internal 10A current source charges the gate of the external N-channel MOSFET. An internal clamp limits the gate voltage to 6.2V above 12VOUT. A resistor and capacitor network from this pin to ground sets the turn-on rate and compensates the active current limit. During turn-off, a 1mA pull-down current discharges 12VGATE to ground. During short circuit or undervoltage lockout, a 160mA pull-down current between 12VGATE and 12VOUT is activated. Exposed Pad (Pin 17, DHD Package): Exposed pad may be left open or connected to device ground. 422312f 7 LTC4223-1/LTC4223-2 FUNCTIONAL DIAGRAM RIN 5k + - A1 12IMON ROUT 165k 10A CHARGE PUMP 12VGATE 60mV 12VIN +- 12VSENSE + - 50mV +- + - 6.2V ACL 1mA 12VOUT GATE DRIVER ECB 12V PWRGD PG2 10.3V VCC 12V SUPPLY CONTROL 12ON + - 10A 12V FET ON 12PGOOD VCC R2 EN CARD PRESENCE VCC 9.7V + - 2.45V + - 12VIN VCC VCC VCC AUXIN 200A 10A 2.5V 0.2V TIMER 1.235V + - + - + - UVLO3 10A FAULT UVLO2 12V FAULT SYSTEM CONTROL UVLO1 CP2 AUX FAULT CP1 VCC 2A 10A AUXPGOOD AUXON AUX FET ON AUX SUPPLY CONTROL GND AUX PWRGD THERMAL SHUTDOWN PG1 + - 2.885V CHARGE PUMP 10A AUXIN AUXOUT RSNS MFET 422312 FD 422312f 8 LTC4223-1/LTC4223-2 OPERATION The LTC4223 is designed to control the power on an Advanced Mezzanine Card (AMC) or MicroTCA backplane, allowing boards to be safely inserted and removed. It controls the 12V main and 3.3V auxiliary power through an external N-channel MOSFET and integrated pass transistor. These two supplies can be turned on and off independently by their respective ON control pins. If either AUXON or 12ON is pulled high, an initial timing cycle set by the TIMER capacitor value is initiated once all these conditions are met: input supplies out of undervoltage lockout; TIMER < 0.2V and EN low. At the end of the initial timing cycle, if the AUXON pin is high, the internal pass transistor turns on. It enters into an active current limit loop if the inrush current charging the load capacitor exceeds 240mA. When the load is in current limit, a 10A pull-up charges the TIMER pin capacitor. If the load capacitor is fully charged and the switch is no longer in current limit before the TIMER reaches 1.235V, AUXPGOOD pulls low indicating that power is good. Otherwise the internal switch turns off and FAULT pulls low when TIMER reaches 1.235V. If 12ON pin is high at the end of the initial timing cycle, an internal charge pump charges the gate of the external MOSFET with 10A pull-up. Connecting an external gate capacitor limits the inrush current charging the load capacitor. If the inrush current exceeds its limited current value, an internal analog current limit (ACL) amplifier servos the gate to force 60mV across the external sense resistor connected between 12VIN and 12VSENSE pins. During this period, TIMER pin capacitor is charged by a 200A pull-up. If the load is fully charged and no longer in current limit before the TIMER reaches 1.235V, 12PGOOD pulls low. Otherwise 12V shuts off and FAULT pulls low when TIMER reaches 1.235V. If an overcurrent fault occurs on the auxiliary supply after power-up, the current is limited to 240mA and after a 25s delay, the circuit breaker trips and FAULT pulls low. Thermal shutdown protects the internal pass transistor from overheating by shutting it off at 150C. If an overcurrent fault occurs on the 12V supply, the current is limited to 60mV/RSENSE. After a timing cycle delay set by 200A charging the TIMER capacitor, the circuit breaker trips and FAULT pulls low. An overcurrent fault on the auxiliary supply shuts off 12V; a fault on the 12V supply does not affect the auxiliary supply. The LTC4223 provides high side current sensing information for the 12V supply at the 12IMON pin. The 12IMON output voltage is 33 times the sense voltage, allowing it to be used with an external ADC. In the off condition, 12VOUT and AUXOUT are discharged to ground by internal N-channel pull downs. 422312f 9 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION RS 6m CARRIER AMC MODULE AMC CONNECTOR CONNECTOR Q1 Si7336ADP PWR 12V BULK SUPPLY BYPASS CAPACITOR 2 5 3.3V R2 51 BULK SUPPLY BYPASS CAPACITOR 6 C2 330nF 7 PWR ENABLE 4 3.3V R6* 10k MP GOOD 3.3V R5* 10k R4* 10k PWR GOOD FAULT 1 16 12VSENSE 12VGATE AUXIN 12VOUT AUXOUT MP ENABLE 3.3V CG RG 15nF 47 R3 10 12VIN 12V 7.4A 15 12 MP 10 PS1 3.3V 150mA VCC AUXON 12ON LTC4223-1 11 14 13 AUXPGOOD 12PGOOD FAULT 3.3V INTELLIGENT PLATFORM MANAGEMENT CONTROLLER 1F 3 7 6 1 CLK 5 8 VREF VCC +IN 2 3 EN 12IMON PS0 DOUT LTC1197L CS 3.3V -IN GND 4 3 GND 8 TIMER 9 2.2k CT 0.1F 422312 F01 3.3V PRESENCE ENABLE RESET 10k *OPTIONAL Figure 1. Advanced Mezzanine Card/MicroTCA Application The typical LTC4223 application is in a Carrier board for Advanced Mezzanine Cards (AMC), delivering 3.3V auxiliary and 12V power to the AMC module. A controller on the Carrier board sequences the turn-on of power supplies and manages the fault and power-good reports from the LTC4223. The LTC4223 detects board presence during insertion and extraction, allowing power to be delivered in a controlled manner without damaging the connector. The typical LTC4223 application circuit is shown in Figure 1. External component selection is discussed in detail in the Design Example section. Turn-On Sequence The power supplies delivered to an AMC module are controlled by the external N-channel pass transistor, Q1 in the 12V power path and an internal pass transistor in the 3.3V auxiliary power path. Sense resistor RS monitors the 12V load current for fault detection and current sensing information. GATE capacitor CG provides gate slew rate control to limit the inrush current. Resistor RG with CG compensates the current control loop while R3 prevents parasitic oscillations in Q1. 422312f 10 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION Several conditions must be met before the external and internal switches are allowed to turn on. First VCC and the input supplies (12VIN, AUXIN) must exceed their undervoltage lockout thresholds. Next TIMER must be <0.2V and EN must be pulled low. Once these conditions are met, a debounce timing cycle is initiated when AUXON or 12ON pin is toggled from low to high. These two control pins turn on/off the 3.3V auxiliary and 12V supplies. At the end of the debounce cycle, the ON pins and fault status are checked. If both ON pins are high and fault is cleared, the 3.3V auxiliary supply starts up first followed by the 12V supply. Note that the turn-on delay for the AUXON and 12ON pins is 15s and 30s. Figure 2 shows the two supplies turning on in sequence after EN goes low. By default, the internal pass transistor turns on first if both ON pins are high and start-up conditions met. The output is current limited at 240mA by its internal ACL amplifier as the load current charging the output capacitor increases. This causes the TIMER to ramp up with a 10A pull-up. Normally the AUXOUT voltage exceeds its power-good threshold before TIMER time-out and then AUXPGOOD pulls low. EN 5V/DIV TIMER 2V/DIV AUXOUT 5V/DIV 12VOUT 5V/DIV AUXPGOOD 5V/DIV 12PGOOD 5V/DIV 20ms/DIV 422312 F02 Figure 2. Normal Power-Up Sequence Once AUXOUT signals power is good and the TIMER pin returns to <0.2V, the external MOSFET is then allowed to turn on by charging up the GATE with a 10A current source (Figure 2). The voltage at the GATE pin rises with a slope equal to 10A/CG and the supply inrush current flowing into the load capacitor CL1 (see Figure 14) is limited to: IINRUSH = CL1 * 10A CG The 12V output follows the GATE voltage when the MOSFET turns on. If the voltage across the current sense resistor RS becomes too high, the inrush current is limited by the internal current limit circuitry. Once the output, 12VOUT exceeds its power-good threshold, 12PGOOD also pulls low. If only the 12ON pin is high at the end of debounce cycle, the external MOSFET turns on first. After that, if AUXON pulls high, the internal switch turns on only after the 12V output signals power is good and TIMER <0.2V. Table 1. 12V and Auxiliary Supply Turn-Off Conditions CONDITION RESULT CLEARED BY AUX 12V AUXON Goes Low Turns Off No Effect 12ON Goes Low No Effect Turns Off 12ON High AUXON High EN Goes High Turns Off Turns Off EN Low UVLO on VCC Turns Off Turns Off VCC > UVLO UVLO on AUXIN Turns Off No Effect AUXIN > UVLO UVLO on 12VIN No Effect Turns Off 12VIN > UVLO AUX Overcurrent Fault Turns Off Turns Off 12V Overcurrent Fault No Effect Turns Off AUXON and 12ON Low, EN High-to-Low, UVLO on VCC High-to12ON Low, E N Low, UVLO on VCC Thermal Shutdown Turns Off Turns Off AUXON and 12ON Low, EN High-to-Low, UVLO on VCC, Temperature < 120C 422312f 11 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION Turn-Off Sequence The switches can be turned off by various conditions and this is summarized in Table 1. When the 12ON pin goes low, the external switch is turned off with the GATE pin pulled to ground by 1mA current sink. The 12PGOOD pin pulls high indicating that power is no longer good, while an internal N-channel transistor discharges the output to ground. Similarly, when the AUXON pin goes low, the internal switch is turned off, AUXPGOOD pulls high while its output is discharged to ground through an internal N-channel transistor. Figure 3 shows the two supplies being turned off by EN going high. Card Presence Detect In an AMC system, PS1 and PS0 signals are used to detect the presence of a card upon insertion or removal. Normally PS1 is connected to the EN pin with a pull-up resistor. If AUXON or 12ON is high when the EN pin goes low, indicating a board insertion, a timing cycle for contact debouncing is initiated. Upon insertion, any bounces on the EN pin will re-start the timing cycle. When TIMER finally reaches its threshold during ramp up, the fault latches will be cleared. If the EN pin remains low at the end of the timing cycle, the switches are allowed to turn on. If the EN pin is toggled from low to high, indicating board removal, all the switches will be turned off after a 20s delay. Any latched faults will not be cleared. However, removing the card could cause the EN pin voltage to bounce, clearing the fault latches undesirably. This is prevented by blanking EN 5V/DIV AUXOUT 5V/DIV the bounces internally with a TIMER ramp up period given by CT * 123[ms/F] as shown in Figure 4. Timer Functions An external capacitor CT connected from the TIMER pin to ground is used to perform several functions. 1. Ignore contact debouncing during card insertion when the device is enabled. The debounce cycle is given by ramping up CT with 10A current to TIMER high threshold (1.235V) and then ramping down with 2A current to below TIMER low threshold (0.2V). This gives an average debounce cycle time of CT * 741[ms/F]. After that, if any ON pin is pulled high and EN pin is low, the switches can be turned on. 2. Blanking contact bounce on the EN pin that might trigger unwanted fault clearing during card removal. The blanking time is given by CT * 123[ms/F]. 3. Fault filtering during auxiliary supply power-up in analog current limit. TIMER pulls up with 10A and pulls down with 2A. The filter time is given by CT * 123[ms/F]. 4. 12V supply fault filtering during and after power-up in analog current limit. TIMER pulls up with 200A and pulls down with 2A. The filter time is given by CT * 6[ms/F]. 5. For cooling off during an auto-retry cycle after an overcurrent fault on auxiliary or 12V supply (LTC4223-2). The cool-off time is given by CT * 1482 [ms/F] after an auxiliary supply fault and CT * 1358[ms/ F] after a 12V supply fault. EN 2V/DIV 12VOUT 5V/DIV TIMER 1V/DIV AUXPGOOD 5V/DIV 12PGOOD 5V/DIV FAULT 2V/DIV 100ms/DIV 422312 F03 Figure 3. Normal Power-Down Sequence 5ms/DIV 422312 F04 Figure 4. Debouncing by TIMER during Card Removal 422312f 12 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION As the TIMER capacitor is used for fault filtering during power-up for both the auxiliary and 12V supplies, only one supply can be started up at any one time. The other supply waits until the power-good signal is generated by the powering-up supply and the TIMER pin voltage falls below 0.2V. By default, the 3.3V auxiliary supply starts up first if both AUXON and 12ON are high at the end of the debounce cycle. Whenever both AUXON and 12ON are pulled low, the device is in reset mode and TIMER capacitor is discharged to ground by an 8mA current sink. Thermal Shutdown The internal 3.3V auxiliary supply switch is protected by thermal shutdown. If the switch's temperature reaches 150C, the aux switch will shut off immediately and FAULT will pull low. The external 12V supply switch also turns off. The switches are allowed to turn on again by cycling both the AUXON and 12ON pins low then high after the internal switch's temperature falls below 120C. Overcurrent Fault The LTC4223 features an adjustable current limit with circuit breaker function that protects the external MOSFET against FAULT 5V/DIV ILOAD 5A/DIV 12VOUT 5V/DIV 12VGATE 5V/DIV 0.1ms/DIV 422312 F05 Figure 5. Overcurrent Fault on 12V Output short circuits or excessive load current on 12V supply. The voltage across the external sense resistor is monitored by the analog current limit (ACL) amplifier and the electronic circuit breaker (ECB) comparator. If an overcurrent fault occurs that causes the sense voltage to reach the ACL threshold (60mV), the ACL amplifier regulates the MOSFET to prevent any further increase in current. This overcurrent condition results in a sense voltage that exceeds the ECB threshold. As a result, the TIMER capacitor is charged by a 200A current. If the condition persists, the TIMER pin voltage will reach its threshold (1.235V). When this occurs, the FAULT pin pulls low and a 1mA current pulls the GATE pin to ground causing the MOSFET to turn off. The circuit breaker time delay, the time required for the TIMER pin capacitor to charge from ground to the TIMER pin threshold, is given by CT * 6[ms/F]. After the MOSFET turns off, the TIMER pin capacitor discharges with a 2A pull-down current. For the auto-retry version (LTC4223-2), if the TIMER discharges to below 0.2V, a new start-up cycle will begin. The TIMER starts ramping up and clears faults when it exceeds 1.235V; thereafter it ramps down (see the section on Auto-Retry for details). Figure 5 shows an overcurrent fault on the 12V output. In the event of a severe short-circuit fault on 12V output as shown in Figure 6, the output current can surge to tens of amperes. The LTC4223 responds within a very short time to bring the current under control by pulling the MOSFET's GATE-to-SOURCE pin voltage down to zero volts. Thereafter, the GATE of the MOSFET recovers rapidly due to the RG/CG compensation network and enters into active current limiting until the TIMER times out. Due to parasitic supply lead inductance, an input supply without any bypass capacitor will collapse during the high current surge and then spike upwards when the current is interrupted. An input supply transient protection network comprising of Z1, R1 and C1 shown in Figure 13 is recommended if there is no input capacitance. 422312f 13 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION There are two different modes of fault time-out for the 3.3V auxiliary supply: adjustable delay through TIMER capacitor during power-up when AUXPGOOD not asserted; fixed 25s delay after power-up when AUXPGOOD asserted low. Under the situation whereby AUXON toggles low then high for short duration after power-up while AUXPGOOD still pulling low due to output load capacitor, 25s fault time-out applies. When the auxiliary supply is powered up into an output short, the ACL amplifier will regulate the gate of the internal pass transistor to produce 240mA output current. At this time a 10A pull-up current starts charging up the TIMER pin capacitor until it exceeds its threshold (1.235V). The internal pass transistor then turns off and FAULT pulls low. Thereafter, the TIMER is discharged by a 2A pull-down current. The fault filter delay is given by CT * 123[ms/F]. After a successful power-up cycle, the ACL amplifier protects the auxiliary supply from overcurrent by pulling down the gate of the internal pass transistor rapidly as shown in Figure 7. Thereafter, the gate recovers and servos the output current to about 240mA for 25s before pulling down to ground gently, turning the transistor off. At this time, FAULT pulls low and the 12V external MOSFET is also turned off by the 1mA GATE pull-down current. Whenever the 3.3V auxiliary supply trips off due to an overcurrent fault, the 12V supply also shuts off. The auxiliary supply is, however, unaffected by faults on the 12V supply. In either case FAULT latches low when the affected channels turn off, and FAULT is cleared by toggling the ON pins. Faults are cleared automatically in the LTC4223-2 auto-retry version. If there is significant supply lead inductance, a severe output short may collapse the input to ground before the LTC4223 can bring the current under control. In this case the undervoltage lockout will activate after a 12s filter delay, and pull the gate down. Then the ACL amplifier will take control and regulate the output in active current limit. Under this situation, the fault time-out is set by TIMER delay instead of 25s filter delay. Undervoltage Fault An undervoltage fault occurs if either AUXIN or 12VIN falls below its undervoltage threshold for longer than 12s. This turns off the affected supply's switch instantly, but does not clear the fault latches. Further, an undervoltage fault on one supply does not affect the operation of the other supply. If the bias supply input, VCC falls below its UVLO threshold for more than 80s, all supply switches are turned off and the fault latches are cleared. Operation resumes from a fresh start-up cycle when VCC is restored. FAULT 5V/DIV VSENSE 200mV/DIV 12VOUT 5V/DIV ILOAD 1A/DIV 12VGATE 5V/DIV AUXOUT 5V/DIV 5s/DIV 422312 F06 Figure 6. Short-Circuit Fault on 12V Output 5s/DIV 422312 F07 Figure 7. Short-Circuit Fault on 3.3VAUX Output 422312f 14 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION Power-Good Monitor Auto-Retry after a Fault (LTC4223-2) Internal circuitry monitors the output voltages, AUXOUT and 12VOUT. The power-good status is reported via their U X P G O O D and 1 2 P G O O D . respective open drain outputs, A Several conditions must be met before the power-good outputs assert low. At time point 1 in Figure 8, if a fault latched-off the 3.3V auxiliary supply after power-up, a cool-off cycle begins. The TIMER capacitor charges up to 1.235V with a 10A current and then discharges with a 2A current to 0.2V at time point 3. This is followed by a debounce timing cycle whereby the fault latch is cleared, and FAULT pulls high when TIMER reaches its threshold at time point 4. At the end of debounce cycle, the internal switch is allowed to turn on. If the output short persists, the auxiliary supply powers up into a short with active current limiting. At time point 7, the fault filter delay begins with TIMER ramping up with a 10A current. If the TIMER times out at time point 8, FAULT will be pulled low and a new cool-off cycle begins with TIMER ramping down with a 2A current. The whole process repeats itself until the output-short is removed. 1. The monitored output should be above its powergood threshold and hysteresis. 2. The input supply is above undervoltage lockout. 3. EN is low. 4. The associated ON pin is high. 5. Thermal shutdown is not activated. If any of the supply outputs falls below its power-good threshold for more than 20s, the respective power-good output will be pulled high by the external pull-up resistor or internal 10A pull-up. Resetting Faults (LTC4223-1) Any supply faults tripping the circuit breaker are latched and FAULT asserts low. For the latched-off version (LTC4223-1), to reset a fault latch due to overcurrent or thermal shutdown on auxiliary supply, pull both AUXON and 12ON pins low together for at least 100s, after which the FA U L T will go high. Toggling both the ON pins high together again initiates the debounce timing cycle, thereafter the auxiliary supply starts up first followed by 12V supply. To skip the debounce timing cycle, first pull only AUXON low then high for at least 50s before toggling 12ON low then high. The fault latch clears on the falling edge of 12ON and the auxiliary supply powers up. Thereafter, the 12V supply powers up if 12ON pulls high. To reset a fault on the 12V supply and re-start the output, toggle only the 12ON pin low and then high again. Toggling the EN pin high then low again or bringing the bias input, VCC below its UVLO threshold for more than 100s will initiate the debounce timing cycle and reset all fault latches before power-up. Bringing AUXIN or 12VIN below its undervoltage threshold will not reset the fault latches. For the auto-retry version (LTC4223-2), the latched fault will be cleared automatically after a cool-off timing cycle. In Figure 9, a fault latches off the 12V supply at time point 1; a cool-off cycle begins by discharging the TIMER capacitor with 2A current from 1.235V to 0.2V threshold. At time point 2 a new debounce timing cycle is initiated where the fault latch is cleared, and FAULT pulls high when TIMER reaches its threshold at time point 3. At the end of the debounce cycle, the 12V GATE is allowed to start up. If the output short persists, the 12V supply powers up into a short with active current limiting. At time point 6, the fault filter delay begins with TIMER ramping up with a 200A current. The TIMER times out at time point 7, FAULT pulls low and a new cool-off cycle begins with TIMER ramping down with a 2A current. The whole process repeats itself until the output-short is removed. The auto-retry duty cycle is given by: DutyCycle = tFILTER * 100% tCOOL + tDEBOUNCE + tFILTER For example, if TIMER capacitor, CT = 0.1F, the auto-retry duty cycle for auxiliary and 12V supply is 6.5% and 0.5% respectively. 422312f 15 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION GATE Pin Voltage The gate drive at 12VGATE is compatible with any logic level MOSFET. The guaranteed range of gate drive is 4.5V to 7.9V, with a typical of 6.2V. Active Current Loop Compensation The compensation network consisting of resistor RG and gate slew rate control capacitor CG stabilizes the internal active current limit circuit. The value of CG is selected based on the inrush current allowed. The suggested value for RG is 47. The value of CG should be 330nF and RG is between 10 and 100 for optimum performance. High Side Current Sense The 12V load current is monitored via the voltage across an external sense resistor. The LTC4223 features a high side current sense amplifier that translates the sense voltage from the positive rail to the negative rail using a resistor ratio of 33 times. The output voltage at 12IMON pin can The internal circuitry of the LTC4223 is powered from the VCC pin. Bypass VCC with at least 330nF to ground. If VCC is derived from the same supply as is AUXIN, include a decoupling resistor as shown in Figure 11. This RC network allows the VCC pin to ride out supply glitches caused by short circuits on the auxiliary output or on adjacent boards, thus preventing an undervoltage lockout condition on VCC. Since the absolute maximum rating for VCC is 7V as compared to 10V for AUXIN, select R2 and C2 to keep the peak voltage seen by VCC below 7V during any voltage spikes. START AUX INTERNAL GATE RAMP WHEN STARTUP CONDITIONS ARE MET AUX OUTPUT IN CURRENT LIMIT START OF DEBOUNCE CYCLE 2 VCC Supply Filtering END OF DEBOUNCE CYCLE FAULT PULLS LOW DUE TO AUX OVERCURRENT FAULT AFTER POWER UP START OF COOL-OFF CYCLE 1 then be fed into an LTC1197L ADC as shown in Figure 10 for data conversion. The current sense information can be used by the system controller to manage the power budget allocated to the modules on the card. Full scale input to the current sense amplifier is 82.5mV, corresponding to an output of about 2.7V. If the input exceeds 100mV, the output clamps at 3.2V. 3 FAULT PULLS LOW AND RESTART OF COOL-OFF CYCLE DURING POWER UP RESET FAULT HIGH 4 5 6 7 8 RESTART OF DEBOUNCE CYCLE 9 10 FAULT 10A VTMR 2A 10A VTMR 2A 10A VTMR 2A 10A VTMR 2A 10A TIMER FILTER DELAY COOL-OFF CYCLE DEBOUNCE CYCLE COOL-OFF CYCLE AUX INTERNAL GATE REGULATES IAUXOUT 12VOUT 422312 F08 Figure 8. Auto-Retry after AUX Overcurrent Fault 422312f 16 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION END OF DEBOUNCE CYCLE FAULT PULLS LOW DUE TO 12V OVERCURRENT FAULT START OF COOL-OFF CYCLE START 12V GATE RAMP WHEN STARTUP CONDITIONS ARE MET 12V OUTPUT IN CURRENT LIMIT START OF DEBOUNCE CYCLE 1 2 FAULT PULLS LOW AND RESTART OF COOL-OFF CYCLE RESET FAULT HIGH 3 4 5 6 7 RESTART OF DEBOUNCE CYCLE 8 FAULT 200A VTMR 2A 10A VTMR 2A 200A VTMR 2A 10A TIMER FILTER DELAY COOL-OFF CYCLE COOL-OFF CYCLE DEBOUNCE CYCLE 12VGATE REGULATES 12VGATE 60mV 60mV 12VIN - 12VSENSE 12VOUT 422312 F08 Figure 9. Auto-Retry after 12V Overcurrent Fault VSENSE - + Q1 12V 12VSENSE 12VIN RIN 5k LOAD 12VGATE - The supply inputs, AUXIN and 12VIN are fed directly from the regulated output of the backplane supply, where bulk bypassing assures a spike-free operating environment. In other applications where the bulk bypassing is located far from the LTC4223, spikes generated during output short circuit events could exceed the absolute maximum ratings for AUXIN and 12VIN. To minimize such spikes, use wider traces or heavier trace plating to reduce the power trace inductance. Also, bypass locally with a 10F electrolytic and 100nF ceramic, or alternatively clamp the input with a transient voltage suppressor (Z1, Z2) as shown in Figure 13. A 10, 100nF snubber damps the response and eliminates ringing. A recommended layout of the 12V transient protection devices Z1, R1 and C1 around the LTC4223 is shown in Figure 12. ILOAD + Supply Transient Protection 1F 12IMON ROUT 165k VOUT VREF +IN VCC LTC1197L CLK DOUT TO SYSTEM CONTROLLER CS -IN LTC4223 3.3V GND 422312 F10 VOUT = ROUT RIN * VSENSE = 33 * VSENSE Figure 10. High Side Current Sense with LTC1197L ADC 422312f 17 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION CURRENT FLOW TO LOAD R2 51 AUXIN C2 330nF SENSE RESISTOR POWER PAK SO-8 CURRENT FLOW TO LOAD VCC 12VIN W 12VOUT W 422312 F11 Figure 11. RC Network for VCC Filtering TRACK WIDTH W: 0.03" PER AMPERE ON 1OZ Cu FOIL R3 12VGATE * RG VIA TO GND PLANE CG PCB Layout Considerations For proper operation of the LTC4223's circuit breaker, Kelvin-connection to the sense resistor is strongly recommended. The PCB layout should be balanced and symmetrical to minimize wiring errors. In addition, the PCB layout for the sense resistor and the power MOSFET should include good thermal management techniques for optimal device power dissipation. A recommended PCB layout for the 12V sense resistor and the power MOSFET is illustrated in Figure 12. In applications where load current exceeds 10A, wide PCB traces are recommended to minimize resistance and temperature rise. The suggested trace width for 1 oz copper foil is 0.03" for each ampere of DC current to keep PCB trace resistance, voltage drop and temperature rise to a minimum. Note that the sheet resistance of 1 oz copper foil is approximately 0.5m/square, and voltage drops due to trace resistance add up quickly in high current applications. In most applications, it will be necessary to use platedthrough via to make circuit connections from component layers to power and ground layers internal to the PCB. For 1 oz copper foil plating, a general rule is 1A of DC current per via. Consult your PCB fabrication facility for design rules pertaining to other plating thicknesses. It is important to place the VCC bypass capacitor C2 as close as possible between VCC and GND. The transient voltage suppressors Z1 and Z2 are also placed between the supply inputs and ground using short wide traces. Z1 1 C1 2 16 LTC4223CGN* 15 8 CURRENT FLOW TO SOURCE VIA TO GND PLANE * GND W GND 422312 F12 *ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE! Figure 12. Recommended Layout for Power MOSFET, Sense Resistor and GATE Components on 12V Rail The first step is to select the appropriate value of RSENSE for the 12V supply. Calculating RSENSE value is based on the maximum load current and the lower limit for the circuit breaker threshold, VSENSE(CB)(MIN). RSENSE = VSENSE(CB)(MIN) ILOAD(MAX ) = 47.5mV = 6m 7.4A A If a 1% tolerance is assumed for the 6m sense resistor, the minimum and maximum circuit breaker trip current is calculated as follows: Table 2. AMC Power Supply Requirements SUPPLY VOLTAGE MAXIMUM LOAD CURRENT MAXIMUM LOAD CAPACITANCE 12V 7.4A 800F 3.3VAUX 150mA 150F Table 3. MicroTCA Power Supply Requirements SUPPLY VOLTAGE MAXIMUM LOAD CURRENT MAXIMUM LOAD CAPACITANCE 12V 7.6A 1600F 3.3VAUX 150mA 150F Design Example As a design example, consider the AMC Hot Swap application shown earlier in Figure 1 with the power supply requirements given in Table 2. R1 422312f 18 LTC4223-1/LTC4223-2 APPLICATIONS INFORMATION ITRIP(MIN) = ITRIP(MAX ) = VSENSE(CB)(MIN) RSENSE(MAX ) = VSENSE(CB)(MAX ) RSENSE(MIN) 47.5m mV = 7.8 A 6.06m = 52.5mV = 8.8 A 5.94m For proper operation, ITRIP(MIN) must exceed the maximum load current with margin, so RSENSE = 6m should suffice for the 12V supply. The second step is to determine the TIMER capacitance based on the time required to charge up completely the output load capacitor on auxiliary supply in active current limit without exceeding the fault filter delay. The worstcase start-up time is calculated using the minimum active current limit value for the auxiliary supply. tSTUP( AUX ) = CL2 * 3.3VAUX 150F * 3.3V = 3ms = 165mA IAUX( ACL)(MIN) For a start-up time of 3ms with a 2x safety margin, the TIMER capacitance is calculated as: CT = 2 * tSTUP( AUX ) 123[ms / F ] = 6ms 0.05F 123[ms / F ] Considering the tolerances for the TIMER charging rate and capacitance, a value of 0.1F (10%) for CT should suffice. Since the TIMER charging rate during fault time-out is 20 times faster for the 12V supply as compared to the auxiliary supply during start-up, this scheme ensures that the external MOSFET will not overheat under any outputshort condition. The fault filter delay for the 12V supply is given by 0.1F * 6[ms/F] = 600s versus 12ms for the auxiliary supply. The next step is to verify that the thermal ratings of the selected external MOSFET for the 12V supply aren't exceeded during power-up or an output-short. Assuming the MOSFET dissipates power only due to inrush current charging the load capacitor, the energy dissipated in the MOSFET during power-up is the same as that stored into the load capacitor. The average power dissipated in the MOSFET is given by: CL1 * 12VOUT2 PAVG = 2 * tCHARGE The inrush current can be limited by using the GATE capacitance (CG) so that the power dissipated in the MOSFET is well within its safe operating area (SOA). For IGATE = 10A and CL1 = 800F, we choose CG = 15nF to set the inrush current to 0.5A. IINRUSH = CL1 * IGATE = 0.5A CG tCHARGE = CL1 * 12VOUT = 19ms IINRUSH This results in PAVG = 3W and the MOSFET selected must be able to tolerate 3W for 19ms. The increase in steady state junction temperature due to power dissipated in the MOSFET is T = PAVG * Zth where Zth is the thermal impedance. Under this condition, the Si7336ADP datasheet's Transient Thermal Impedance plot indicates that the junction temperature will increase by 2.4C using ZthJC = 0.8C/W (single pulse). The duration and magnitude of the power pulse that results during a short-circuit condition on the 12V output are a function of the TIMER capacitance and LTC4223's analog current limit. The short-circuit duration is given as 0.1F * 6[ms/F] = 600s for CT = 0.1F. The maximum shortcircuit current is calculated using the maximum analog current limit threshold, VSENSE(ACL)(MAX) and minimum RSENSE value. ISHORT(MAX ) = VSENSE( ACL)(MAX ) RSENSE(MIN) = mV 66m = 11A 5.94m So the maximum power dissipated in the MOSFET is 11A * 12V or 132W for 600s. The Si7336ADP datasheet's Transient Thermal Impedance plot indicates that the worse-case increase in junction temperature during the short-circuit condition is 13.2C using ZthJC = 0.1C/W (single pulse). This will not cause the maximum junction temperature to be exceeded. The SOA curves of the Si7336ADP are also checked to be safe under this condition. 422312f 19 LTC4223-1/LTC4223-2 TYPICAL APPLICATION Card Resident Application with 5V Auxiliary Supply BACKPLANE CARD CONNECTOR CONNECTOR RS 4m Q1 Si7336ADP 12V 10A 12V Z1 SMAJ13A R1 10 R3 10 C1 100nF 12VIN + CG RG 15nF 47 CL1 1000F 12VSENSE 12VGATE 12VOUT 5V AUXIN R6 Z2 10k SMAJ7.0A R7 2.7 C3 100nF 5VAUX 150mA AUXOUT R2 51 C2 330nF + PWRFLT FAULT PWREN AUXON 5V R8 10k BD_SEL CL2 150F VCC LTC4223-1 AUXPGOOD 12ON 5V R4 10k R5 10k 12PGOOD EN 5V 1F GND 12IMON +IN VREF VCC LTC1197 TIMER GND CT 0.1F CLK DOUT TO SYSTEM CONTROLLER CS -IN GND 422312 TA02 422312f 20 LTC4223-1/LTC4223-2 TYPICAL APPLICATION Card Resident Application with 12V Power Up First Followed by 3.3V Auxiliary BACKPLANE CARD CONNECTOR CONNECTOR RS 4m Q1 Si7336ADP 12V 10A 12V R1 10 Z1 SMAJ13A R3 10 C1 100nF 12VIN + CG RG 15nF 47 CL1 1000F 12VSENSE 12VGATE 12VOUT 3.3V AUXIN R7 2.7 C3 100nF Z2 SMAJ5.0A 3.3VAUX 150mA AUXOUT R2 51 C2 330nF PWREN + VCC CL2 150F 12ON R8 10k 3.3V R9 10k 3.3V 3.3V R5 10k 3.3V Q2 2N7002K R4 10k LTC4223-1 AUXPGOOD AUXON 12PGOOD R6 10k 3.3V PWRFLT FAULT BD_SEL EN 1F GND 12IMON +IN VREF VCC LTC1197L TIMER GND CT 0.1F -IN CLK DOUT TO SYSTEM CONTROLLER CS GND 422312 TA03 422312f 21 LTC4223-1/LTC4223-2 PACKAGE DESCRIPTION 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) .0532 - .0688 (1.35 - 1.75) 2 3 4 5 6 7 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 422312f 22 LTC4223-1/LTC4223-2 PACKAGE DESCRIPTION DHD Package 16-Lead Plastic DFN (5mm x 4mm) (Reference LTC DWG # 05-08-1707) 0.70 0.05 4.50 0.05 3.10 0.05 2.44 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 4.34 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5.00 0.10 (2 SIDES) R = 0.20 TYP 4.00 0.10 (2 SIDES) 9 0.40 0.10 16 2.44 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHD16) DFN 0504 8 0.200 REF 1 0.25 0.05 0.50 BSC 0.75 0.05 0.00 - 0.05 4.34 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJGD-2) IN JEDEC PACKAGE OUTLINE MO-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 422312f 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. 23 LTC4223-1/LTC4223-2 TYPICAL APPLICATION 12V/18A Card Resident Application BACKPLANE CARD CONNECTOR CONNECTOR RS 2.5m Q1 HAT2160H 12V 18A 12V R1 10 Z1 SMAJ13A R3 10 C1 100nF 12VIN + CG RG 15nF 47 CL1 1000F 12VSENSE 12VGATE 12VOUT 3.3V AUXIN Z2 SMAJ5.0A R7 2.7 C3 100nF 3.3VAUX 150mA AUXOUT R2 51 + CL2 150F VCC C2 330nF 3.3V R9 10k AUXON R8 10k BD_SEL R4 10k LTC4223-1 R5 10k R6 10k AUXPGOOD 12PGOOD FAULT 12ON EN 3..3V 1F 12IMON +IN VREF VCC LTC1197L TIMER GND CLK DOUT -IN TO CONTROLLER CS GND CT 0.1F 422312 TA04 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1421 Dual Channel, Hot Swap Controller Operates from 3V to 12V, Supports -12V, SSOP-24 LTC1645 Dual Channel, Hot Swap Controller Operates from 3V to 12V, Power Sequencing, SO-8 or SO14 LTC1647-1/LTC1647-2/ Dual Channel, Hot Swap Controller LTC1647-3 Operates from 2.7V to 16.5V, SO-8 or SSOP-16 LTC4210 Single Channel, Hot Swap Controller Operates from 2.7V to 16.5V, Active Current Limiting, SOT23-6 LTC4211 Single Channel, Hot Swap Controller Operates from 2.7V to 16.5V, Multifunction Current Control, MSOP-8 or MSOP-10 LTC4215 Single Channel, Hot Swap Controller Operates from 2.9V to 15V, I2C Compatible Monitoring, SSOP-16 or QFN-24 (4mm x 5mm) LTC4216 Single Channel, Hot Swap Controller Operates from 0V to 6V, MSOP-10 or DFN-12 (4mm x 3mm) LTC4221 Dual Channel, Hot Swap Controller Operates from 1V to 13.5V, Multifunction Current Control, SSOP-16 LTC4245 Multiple Channel, Hot Swap Controller 3.3V, 5V, 12V Supplies, I2C Compatible Monitoring, SSOP-36 or QFN-38 (5mm x 7mm) LTC4252-1/LTC4252-2/ -48V Hot Swap Controller LTC4252A-1/ LTC4252A-2 Fast Active Current Limiting with Drain Accelerated Response, Supplies from -15V, MSOP-8 or MSOP-10 422312f 24 Linear Technology Corporation LT 0807 * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com (c) LINEAR TECHNOLOGY CORPORATION 2007