LTC1421

Allows Safe Insertion into Live AMC or MicroTCA Backplane■ Controls 12V Main and 3.3V Auxiliary Supplies■ Limits Peak Fault Current in ≤1μs■ Adjustable Current Limit with Circuit Breaker■ Integrated 0.3Ω 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 × 4mm DFN Packages■LTC4223-1/LTC4223-2Dual Supply Hot Swap Controller for Advanced Mezzanine CardDESCRIPTION

The LTC®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 sup-ply 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.APPLICATIONS

Advanced Mezzanine Card, MicroTCA Systems ■ Workstations and Server I/O■ Telecom Networks■TYPICAL APPLICATION

Advanced Mezzanine Card Application6mΩ12V15nFSi7336ADP12V7.4ANormal Power-Up WaveformEN5V/DIVAUXOUT5V/DIV

10Ω47Ω12VIN3.3V51ΩVCC330nFAUXIN12VSENSE12VGATE12VOUT3.3V150mA12VOUT5V/DIVAUXPGOOD

5V/DIV12PGOOD5V/DIV

AUXOUTAUXON12ONAUXPGOOD12PGOODFAULTIPMCADC12IMONGNDLTC4223-1/LTC4223-220ms/DIV

422312 TA01b

ENTIMER0.1μF422312 TA01aCARRIERMODULECONNECTORCONNECTOR

422312f1

LTC4223-1/LTC4223-2ABSOLUTE MAXIMUM RATINGS

(Note 1)Supply Voltages 12VIN .....................................................–0.3V to 20V AUXIN ....................................................–0.3V to 10V...........................................................–0.3V to 7V VCC Input Voltages EN ...................................–0.3V to 7V 12ON, AUXON, TIMER ..........................................–0.3V to VCC + 0.3V 12VSENSE ...............................................–0.3V to 20VOutput 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 10VOperating Temperature Range LTC4223-1C/ LTC4223-2C .......................0°C to 70°C LTC4223-1I/ LTC4223-2I .....................–40°C to 85°C Storage Temperature Range GN Package .......................................–65°C to 150°C DHD Package .....................................–65°C to 125°CLead Temperature (Soldering, 10sec) GN Package ......................................................300°CPIN CONFIGURATION

TOP VIEWTOP VIEW12VSENSE12VIN12IMON12ONAUXINVCCAUXONGND123456781612VGATE1512VOUT1412PGOOD13FAULT12AUXOUT11AUXPGOOD10EN9TIMERDHD PACKAGE16-LEAD (5mm × 4mm) PLASTIC DFN12VSENSE12VIN12IMON12ONAUXINVCCAUXONGND12345678171612VGATE1512VOUT1412PGOOD13FAULT12AUXOUT11AUXPGOOD10EN9TIMERGN PACKAGE16-LEAD PLASTIC SSOPTJMAX = 125°C, θJA = 110°C/WEXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONALMUST BE SOLDERED TO PCB TO OBTAINθJA = 43°C/W, OTHERWISE θJA = 140°C/W, TJMAX = 125°CORDER INFORMATION

LEAD FREE FINISHLTC4223CDHD-1#PBFLTC4223CDHD-2#PBFLTC4223IDHD-1#PBFLTC4223IDHD-2#PBFLTC4223CGN-1#PBFLTC4223CGN-2#PBFLTC4223IGN-1#PBFLTC4223IGN-2#PBFTAPE AND REELLTC4223CDHD-1#TRPBFLTC4223CDHD-2#TRPBFLTC4223IDHD-1#TRPBFLTC4223IDHD-2#TRPBFLTC4223CGN-1#TRPBFLTC4223CGN-2#TRPBFLTC4223IGN-1#TRPBFLTC4223IGN-2#TRPBFPART MARKING*4223142232422314223242231422324223I14223I2PACKAGE DESCRIPTION16-Lead (5mm × 4mm) Plastic DFN16-Lead (5mm × 4mm) Plastic DFN16-Lead (5mm × 4mm) Plastic DFN16-Lead (5mm × 4mm) Plastic DFN16-Lead Plastic SSOP16-Lead Plastic SSOP16-Lead Plastic SSOP16-Lead Plastic SSOPTEMPERATURE RANGE0°C to 70°C0°C to 70°C–40°C to 85°C–40°C to 85°C0°C to 70°C0°C to 70°C–40°C to 85°C–40°C to 85°CConsult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.Consult LTC Marketing for information on non-standard lead based fi nish parts.For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/422312f2

LTC4223-1/LTC4223-2ELECTRICAL CHARACTERISTICS The ● denotes the specifi cations which apply over the full operating SYMBOLSuppliesVDDInput Supply RangeVCCAUXIN12VINVCCAUXIN12VINVCC RisingVAUXIN RisingV12VIN RisingVCCAUXIN12VIN●●●●●●●●●●●● ed. (Note 2)temperature range, otherwise specifi cations are TA = 25°C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specifiPARAMETERCONDITIONSMIN2.72.7100.80.40.62.32.49.44070702.452.59.7110110110TYPMAX66142112.62.610180150150UNITSVVVmAmAmAVVVmVmVmVIDDInput Supply CurrentVDD(UVLO)Input Supply Undervoltage LockoutΔVDD(UVLO, HYST)Input Supply Undervoltage Lockout HysteresisCurrent LimitΔVSENSE(CB)ΔVSENSE(ACL)IAUX(ACL)RDS(ON)Gate DriveΔVGATEIGATE(UP)IGATE(DN)IGATE(FPD)Current SenseG12IMONV12IMONΔVSENSE(MAX)V12IMON(CLP)R12IMONV12IMON(MIN)VPG(TH)VPG(HYST)VTMR(TH)12IMON Pin Gain RatioΔV12IMON/Δ(V12VIN – V12VSENSE)12IMON Pin Output Voltage12IMON Pin Maximum Input Sense Voltage12IMON Pin Clamp Voltage12IMON Pin Output Resistance12IMON Pin Minimum Output VoltagePower Good Threshold VoltagePower Good HysteresisTIMER Pin Threshold Voltage(V12VIN – V12VSENSE) = 150mV, VCC = 2.7V(V12VIN – V12VSENSE) = 0V(V12VIN – V12VSENSE) = 0VV12VOUT FallingVAUXOUT FallingV12VOUTVAUXOUTVTIMER RisingVTIMER Falling(V12VIN – V12VSENSE) = (75mV, 25mV)(V12VIN – V12VSENSE) = 75mV, VCC = 2.7V●●●●●●Circuit Breaker Trip Sense Voltage,(V12VIN – V12VSENSE)Active Current Limit Sense Voltage,(V12VIN – V12VSENSE)AUXOUT Active Current LimitSwitch Resistance(VAUXIN – VAUXOUT)/IAUXOUTExternal N-Channel Gate Drive(V12VGATE – V12VOUT)External N-Channel Gate Pull-Up CurrentExternal N-Channel Gate Pull-Down CurrentExternal N-Channel Gate Fast Pull-Down CurrentVAUXOUT = 0VIAUXOUT = 150mA (Note 4)●●●47.55416550602400.352.5663300.5mVmVmAΩIntegrated Switch●(Note 3)Gate Drive On, V12VGATE = 0VGate Drive OffV12VGATE = 17V, V12VOUT = 12VFast Turn OffV12VGATE = 17V, V12VOUT = 12V●●●●4.5–70.5906.2–1011607.9–142250VμAmAmA302.2582.52.9115332.4753.21650362.73.521513010.62.97110301.2720.25V/VVmVVkΩmVVVmVmVVVComparator Inputs●●●●●●102.82051.1980.1510.32.88560161.2350.2422312f3

LTC4223-1/LTC4223-2ELECTRICAL CHARACTERISTICS The ● denotes the specifi cations which apply over the full operating SYMBOLITMR(UP)PARAMETERTIMER Pull-Up CurrentCONDITIONSVTIMER = 1V, Initial Timing CycleVTIMER = 0V, In AUX Fault ModeVTIMER = 0V, In 12V Fault ModeVTIMER = 2V, No FaultsVTIMER = 2V, In Reset ModeIOL = 3mA(Note 5)VPU = 1.5V●●●●●temperature range, otherwise specifi cations are TA = 25°C, VCC = 3.3V, VAUXIN = 3.3V, V12VIN =12V, unless otherwise specifi ed. (Note 2)MIN–7–7–1401.32TYP–10–10–200280.15VCC – 1–6–10–14MAX–13–13–2602.6160.4UNITSμAμAμAμAmAVVμAITMR(DN)TIMER Pull-Down CurrentOpen Drain OutputsVOLVOHIPULogic InputsVIN(TH)IIN(LEAK)RPUI12VSENSEI12VOUTROUT(DIS)Logic Input Threshold (12ON, AUXON, EN)Input Leakage Current (12ON, AUXON)EN Pin Pull-Up Resistance12VSENSE Pin Input Current12VOUT Pin Input CurrentOUT Pin Discharge Resistance12VOUTAUXOUTAUX Circuit Breaker Trip DelaySense Voltage, (12VIN – 12VSENSE)High to 12VGATE LowAUXON High to AUXOUT High12ON High to 12VGATE HighInput Low (12ON, AUXON) to FAULT HighVCC Low to FAULT High12VIN Low to 12VGATE LowAUXIN Low to AUXPGOOD HightPHL(GATE)tPLH(PG)tP(12IMON)EN High to 12VGATE Low12VOUT Low to 12PGOOD HighAUXOUT Low to AUXPGOOD HighInput Sense Voltage Step to 12IMON Propagation DelayΔVSENSE = 100mVV12VSENSE = 12VGate Drive On, V12VOUT = 12VGate Drive OffV12VOUT = 6VVAUXVOUT = 2VAfter Power UpΔVSENSE = 300mV, C12VGATE = 10nFΔVSENSE = 100mV, C12VGATE = 10nFVIN = VCC●●●AULT, 12PGOOD, Output Low Voltage (FAUXPGOOD)AULT, 12PGOOD, Output High Voltage (FAUXPGOOD)AULT, Output Pin Pull-Up Current (F12PGOOD, AUXPGOOD)●●●0.8601020400375121005050800750250.551530208066121220202022±1140100100160015005011230604015018184040406VμAkΩμAμAΩΩμsμsμsμsμsμsμsμsμsμsμsμsμsOther Pin Functions●●●●Propagation DelaystCBtPHL(SENSE)tPHH(AUXON)tPHH(12ON)tRST(ON)tRST(VCC)tPLL(UVLO)●●●●●●●●●●●●●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 specifi ed. 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.AULT, 12PGOOD and AUXPGOOD have an internal Note 5: The output pins Fpull-up to VCC of 10μA. However, an external pull-up resistor may be used when faster rise time is required or for VOH voltages greater than VCC.422312f4

LTC4223-1/LTC4223-2TYPICAL PERFORMANCE CHARACTERISTICS ed.3.3V, V12VIN =12V, unless otherwise specifiICC vs VCC1.6

1.0

Specifi cations are TA = 25°C, VCC = 3.3V, VAUXIN = 12IMON Gain Ratio vs Temperature35

Supply Current vs TemperatureSUPPLY CURRENT (mA)1.2ICC (mA)12IMON GAIN RATIO (V/V)75

100

0.8

VCC12VINAUXIN34

0.6

0.833

0.4

0.432

0.20–50

0

2.53.03.5

4.04.5VCC (V)

5.05.56.0–25

02550TEMPERATURE (°C)

31–50

–25

02550TEMPERATURE (°C)

70100

422312 G01422312 G02422312 G03

12IMON Output Voltage vs Sense Voltage4

10.412VOUT POWER-GOOD THRESHOLD (V)12VOUT Power-Good Threshold vs Temperature2.92AUXOUT POWER-GOOD THRESHOLD (V)AUXOUT Power-Good Threshold vs Temperature12IMON OUTPUT VOLTAGE (V)310.3

RISINGFALLING2.90RISINGFALLING2.88

210.2

110.12.86

0

020

406080100SENSE VOLTAGE (mV)

120140

10.0

–50

–25

02550TEMPERATURE (°C)

75100

2.84

–50

–25

02550TEMPERATURE (°C)

75100

422312 G04422312 G05422312 G06

Circuit Breaker Trip Voltage vs TemperatureACTIVE CURRENT LIMIT SENSE VOLTAGE (mV)52CIRCUIT BREAKER TRIP VOLTAGE (mV)62

Active Current Limit Sense Voltage vs Temperature250AUX ACTIVE CURRENT LIMIT (mA)–25

02550TEMPERATURE (°C)

75

100

AUX Active Current Limit vs Temperature5161

240

230

5060

220

4959

210200–50

48–50

–25

02550TEMPERATURE (°C)

75100

58–50

–25

02550TEMPERATURE (°C)

75100

422312 G07422312 G08422312 G09

422312f5

LTC4223-1/LTC4223-2TYPICAL PERFORMANCE CHARACTERISTICS 3.3V, V12VIN =12V, unless otherwise specifi ed.AUX Switch On Resistance vs Temperature0.5AUX SWITCH-ON RESISTANCE (Ω)6.3

Specifi cations are TA = 25°C, VCC = 3.3V, VAUXIN = Gate Drive vs Temperature76

GATE DRIVE (ΔVGATE) (V)Gate Drive vs IGATE0.46.2

GATE DRIVE (ΔVGATE) (V)54321

0.36.1

0.26.0

0.1

–50

–25

02550TEMPERATURE (°C)

75100

5.9–50

–25

02550TEMPERATURE (°C)

75100

0

0–2–4

–8–6

IGATE (μA)

–10–12

422312 G10422312 G11422312 G12

Gate Pull-Up Current vs Temperature–11.0

AUX CIRCUIT BREAKER TRIP DELAY (µs)30

AUX Circuit Breaker Trip Delay vs Temperature100ACTIVE CURRENT LIMIT DELAY (µs)Active Current Limit Delay vs Sense VoltageGATE PULL-UP CURRENT (µA)–10.510

25

–10.01

20

–9.50.1

–9.0

–50

–25

02550TEMPERATURE (°C)

75100

15–50

–25

02550TEMPERATURE (°C)

75100

0.01

50

100

150200250SENSE VOLTAGE (mV)

300

422312 G13422312 G14

422312 G15

Gate Fast Pull-Down Current vs Temperature250GATE FAST PULL-DOWN CURRENT (mA)OUTPUT DISCHARGE RESISTANCE (Ω)1200

Output Discharge Resistance vs Temperature3.02.5

Logic Input Threshold vs VCC200

1000

12VOUT800

AUXOUT600

LOGIC INPUT THRESHOLD (V)HIGH2.0

LOW1.51.00.502.5

150

100

400200–50

50–50

–25

02550TEMPERATURE (°C)

75100–25

02550TEMPERATURE (°C)

751003.03.5

4.04.5VCC (V)

5.05.56.0

422312 G16422312 G17422312 G18

422312f6

LTC4223-1/LTC4223-2PIN 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 fi lter 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 ris-ing 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 0.3Ω 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 transi-tion 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/μF duration for initial timing cycle, 123ms/μF for AUX current limit during power-up and 6ms/μF 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 10μA 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 750Ω 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 10μA 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. 2PGOOD (Pin 14): 12V Supply Power Status Output. 1Open drain output that is normally pulled high by an in-ternal 10μA 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 N-channel 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 800Ω active pull-down.12VGATE (Pin 16): Gate Drive for 12V Supply External N-Channel MOSFET. An internal 10μA 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.422312f7

LTC4223-1/LTC4223-2FUNCTIONAL DIAGRAM

RIN5k–+

+–A112IMON10μACHARGEPUMP60mVROUT165k12VGATE6.2V1mAGATEDRIVER12VOUT12VIN12VSENSE+–50mV+–+–ACL+–ECB12V PWRGDVCCPG210.3V12V SUPPLYCONTROL12ON12V FET ON10μA12PGOODVCCR2–+ENCARD PRESENCEVCC12VIN9.7V+–+–+–+–+–UVLO310μAFAULT12V FAULTVCC2.45VVCC200μAVCC10μAAUXIN2.5V0.2VUVLO2SYSTEMCONTROLUVLO1CP2TIMERAUX FAULTCP1VCC10μAAUXPGOOD1.235V2μAAUXONAUX FET ONGNDAUX SUPPLYCONTROLAUX PWRGDTHERMALSHUTDOWNPG1CHARGEPUMPAUXINRSNSMFET422312 FD

2.885V10μAAUXOUT422312f8

LTC4223-1/LTC4223-2OPERATION

The LTC4223 is designed to control the power on an Ad-vanced 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 tim-ing 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 10μA 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 10μA pull-up. Connecting an external gate capacitor limits the inrush current charging the load ca-pacitor. If the inrush current exceeds its limited current value, an internal analog current limit (ACL) amplifi er 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 200μA 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 25μs delay, the circuit breaker trips and FAULT pulls low. Ther-mal shutdown protects the internal pass transistor from overheating by shutting it off at 150°C. If an overcurrent fault occurs on the 12V supply, the current is limited to 60mV/RSENSE. After a timing cycle delay set by 200μA 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 informa-tion 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.422312f9

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

RS6mΩ12VBULK SUPPLYBYPASS CAPACITOR25R251Ω12VINAUXIN1R310Ω161512MP3.3V150mACGRG15nF47ΩQ1Si7336ADPCARRIER AMCMODULE AMCCONNECTORCONNECTORPWR12V7.4A12VSENSE12VGATE12VOUTAUXOUT3.3VBULK SUPPLYBYPASS CAPACITORMP ENABLEPWR ENABLE3.3V3.3V3.3VR4*10k6C2330nF74VCCAUXON12ONLTC4223-1MP GOODPWR GOODFAULTR6*10kR5*10k111413AUXPGOOD12PGOODFAULT3.3VINTELLIGENTPLATFORMMANAGEMENTCONTROLLER37613.3V2.2kPRESENCEENABLE*OPTIONALCLK1μF5VREF8VCC+IN2312IMONEN10PS1PS0DOUTLTC1197LCSGND4–IN3GND89TIMERCT0.1μF422312 F013.3V10kRESETFigure 1. Advanced Mezzanine Card/MicroTCA ApplicationThe 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 control-ler 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 SequenceThe 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. 422312f10

LTC4223-1/LTC4223-2APPLICATIONS 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 fi rst followed by the 12V supply. Note that the turn-on delay for the AUXON and 12ON pins is 15μs and 30μs. Figure 2 shows the two supplies turning on in sequence after EN goes low.By default, the internal pass transistor turns on fi rst if both ON pins are high and start-up conditions met. The output is current limited at 240mA by its internal ACL amplifi er as the load current charging the output capaci-tor increases. This causes the TIMER to ramp up with a 10μA pull-up. Normally the AUXOUT voltage exceeds its power-good threshold before TIMER time-out and then AUXPGOOD pulls low.EN5V/DIVTIMER2V/DIVAUXOUT5V/DIV12VOUT5V/DIVAUXPGOOD

5V/DIV12PGOOD5V/DIV

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 10μA current source (Figure 2). The voltage at the GATE pin rises with a slope owing equal to 10μA/CG and the supply inrush current flinto the load capacitor CL1 (see Figure 14) is limited to: IINRUSH=

CL1•10µACG

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 fi rst. 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 ConditionsCONDITIONAUXAUXON Goes Low12ON Goes LowEN Goes HighUVLO on VCCUVLO on AUXINUVLO on 12VINAUX Overcurrent Fault12V Overcurrent FaultThermal ShutdownTurns OffNo EffectTurns OffTurns OffTurns OffNo EffectTurns OffRESULT12VNo Effect Turns OffTurns OffTurns OffNo EffectTurns OffTurns OffAUXON High12ON HighEN LowVCC > UVLOAUXIN > UVLO12VIN > UVLOAUXON and 12ON Low, EN High-to-Low, UVLO on VCCN High-to-12ON Low, ELow, UVLO on VCCAUXON and 12ON Low, EN High-to-Low, UVLO on VCC, Temperature < 120°CCLEARED BYNo EffectTurns OffTurns OffTurns Off20ms/DIV

422312 F02

Figure 2. Normal Power-Up Sequence422312f11

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

Turn-Off SequenceThe 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 dis-charges 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 DetectIn 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 fi nally 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 20μs 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 EN5V/DIVAUXOUT5V/DIV

the bounces internally with a TIMER ramp up period given by CT • 123[ms/μF] as shown in Figure 4.Timer FunctionsAn 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 10μA current to TIMER high threshold (1.235V) and then ramping down with 2μA current to below TIMER low threshold (0.2V). This gives an average debounce cycle time of CT • 741[ms/μF]. 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/μF].3. Fault fi ltering during auxiliary supply power-up in analog current limit. TIMER pulls up with 10μA and pulls down with 2μA. The fi lter time is given by CT • 123[ms/μF].4. 12V supply fault fi ltering during and after power-up in analog current limit. TIMER pulls up with 200μA and pulls down with 2μA. The fi lter time is given byCT • 6[ms/μF].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/μF] after an auxiliary supply fault and CT • 1358[ms/μF] after a 12V supply fault.EN2V/DIV

12VOUT5V/DIVAUXPGOOD

5V/DIV12PGOOD5V/DIV

TIMER1V/DIV

FAULT2V/DIV

100ms/DIV

422312 F03

5ms/DIV

422312 F04

Figure 3. Normal Power-Down SequenceFigure 4. Debouncing by TIMER during Card Removal422312f12

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

As the TIMER capacitor is used for fault fi ltering 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 fi rst if both AUXON and 12ON are high at the end of the debounce cycle. Whenever both AUXON and 12ON are pulled low, the de-vice is in reset mode and TIMER capacitor is discharged to ground by an 8mA current sink.Thermal ShutdownThe internal 3.3V auxiliary supply switch is protected by thermal shutdown. If the switch’s temperature reaches 150°C, 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 120°C.Overcurrent FaultThe LTC4223 features an adjustable current limit with circuit breaker function that protects the external MOSFET against FAULT5V/DIVILOAD5A/DIV12VOUT5V/DIV

short circuits or excessive load current on 12V supply. The voltage across the external sense resistor is monitored by the analog current limit (ACL) amplifi er 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 amplifi er 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 200μA 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/μF].After the MOSFET turns off, the TIMER pin capacitor dis-charges with a 2μA 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 cur-rent 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 recom-mended if there is no input capacitance.12VGATE5V/DIV

0.1ms/DIV

422312 F05

Figure 5. Overcurrent Fault on 12V Output422312f13

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

There are two different modes of fault time-out for the 3.3V auxiliary supply: adjustable delay through TIMER capacitor xed during power-up when AUXPGOOD not asserted; fi25μs 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, 25μs fault time-out applies. When the auxiliary supply is powered up into an output short, the ACL amplifi er will regulate the gate of the internal pass transistor to produce 240mA output cur-rent. At this time a 10μA 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 2μA pull-down current. The fault fi lter delay is given by CT • 123[ms/μF]. After a successful power-up cycle, the ACL amplifi er pro-tects 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 25μs 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 tog-gling the ON pins. Faults are cleared automatically in the LTC4223-2 auto-retry version.If there is signifi cant 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 12μs fi lter delay, and pull the gate down. Then the ACL amplifi er 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 25μs fi lter delay.Undervoltage FaultAn undervoltage fault occurs if either AUXIN or 12VIN falls below its undervoltage threshold for longer than 12μs. 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 80μs, all supply switches are turned off and the fault latches are cleared. Operation resumes from a fresh start-up cycle when VCC is restored.FAULT5V/DIV

ΔVSENSE200mV/DIV

12VOUT5V/DIV

ILOAD1A/DIV

12VGATE5V/DIV

AUXOUT5V/DIV

5μs/DIV

422312 F06

5μs/DIV

422312 F07

Figure 6. Short-Circuit Fault on 12V OutputFigure 7. Short-Circuit Fault on 3.3VAUX Output422312f14

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

Power-Good MonitorInternal circuitry monitors the output voltages, AUXOUT and 12VOUT. The power-good status is reported via their UXPGOOD and 12PGOOD. respective open drain outputs, ASeveral conditions must be met before the power-good outputs assert low.1. The monitored output should be above its power-good 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 20μs, the respective power-good output will be pulled high by the external pull-up resistor or internal 10μA 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 100μs, after which the AULT will go high. Toggling both the ON pins high together Fagain initiates the debounce timing cycle, thereafter the auxiliary supply starts up fi rst followed by 12V supply. To skip the debounce timing cycle, fi rst pull only AUXON low then high for at least 50μs 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. Tog-gling the EN pin high then low again or bringing the bias input, VCC below its UVLO threshold for more than 100μs 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.Auto-Retry after a Fault (LTC4223-2)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 10μA current and then discharges with a 2μA 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 fi lter delay begins with TIMER ramping up with a 10μA 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 2μA current. The whole process repeats itself until the output-short is removed.In Figure 9, a fault latches off the 12V supply at time point 1; a cool-off cycle begins by discharging the TIMER ca-pacitor with 2μA 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 fi lter delay begins with TIMER ramping up with a 200μA 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 2μA 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 = 0.1μF, the auto-retry duty cycle for auxiliary and 12V supply is 6.5% and 0.5% respectively. 422312f15

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

GATE Pin VoltageThe 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 CompensationThe 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 47Ω. The value of CG should be ≤330nF and RG is between 10Ω and 100Ω for optimum performance.High Side Current SenseThe 12V load current is monitored via the voltage across an external sense resistor. The LTC4223 features a high side current sense amplifi er 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 FAULT PULLS LOW DUE TO AUX

OVERCURRENT FAULT AFTER POWER UPSTART OF COOL-OFF CYCLE

START OF

DEBOUNCE CYCLERESET FAULT HIGHthen 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 amplifi er is 82.5mV, corresponding to an output of about 2.7V. If the input exceeds 100mV, the output clamps at 3.2V.VCC Supply FilteringThe 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 net-work 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 condi-tion 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 METAUX OUTPUT IN CURRENT LIMITFAULT PULLS LOW AND RESTART OFCOOL-OFF CYCLE DURING POWER UPRESTART OFDEBOUNCE CYCLEEND OF DEBOUNCE CYCLE12345678910FAULT

10μATIMER

VTMR2μA10μAVTMR2μA10μAVTMR2μA10μAVTMR2μA10μAFILTER DELAYCOOL-OFF CYCLEDEBOUNCE CYCLECOOL-OFF CYCLEAUX INTERNAL GATE REGULATESIAUXOUT

12VOUT

422312 F08Figure 8. Auto-Retry after AUX Overcurrent Fault422312f16

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

FAULT PULLS LOW DUE TO12V OVERCURRENT FAULTSTART OF COOL-OFF CYCLE

START OF

DEBOUNCE CYCLERESET FAULT HIGHEND OF DEBOUNCE CYCLESTART 12V GATE RAMP WHEN STARTUP CONDITIONS ARE MET12V OUTPUT IN CURRENT LIMIT

FAULT PULLS LOW AND

RESTART OF COOL-OFF CYCLERESTART OF

DEBOUNCE CYCLE12345678FAULT

200μATIMER

VTMR2μA10μAVTMR2μA200μAVTMR2μA10μA

FILTER DELAYCOOL-OFF CYCLEDEBOUNCE CYCLECOOL-OFF CYCLE12VGATE REGULATES12VGATE

60mV60mV12VIN - 12VSENSE

12VOUT

422312 F08Figure 9. Auto-Retry after 12V Overcurrent FaultSupply Transient ProtectionThe 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 10μF electrolytic and 100nF ceramic, or alternatively clamp the input with a transient voltage suppressor (Z1, Z2) as shown in Figure 13. A 10Ω, 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

Q1VSENSE– +12V12VSENSE12VINRIN5k12VGATELOAD1μF12IMONVOUTVREFLTC1197L–INGND422312 F103.3V+INVCCCLKTO SYSTEMCONTROLLERROUT165kLTC4223DOUTCSVOUT =

ROUTRIN

• VSENSE = 33 • VSENSE

Figure 10. High Side Current Sense with LTC1197L ADC422312f17

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

R251Ω

AUXIN

C2330nFVCC

12VIN

WW12VOUT

CURRENT FLOWTO LOADSENSERESISTORPOWER PAK

SO-8CURRENT FLOWTO LOAD422312 F11

Figure 11. RC Network for VCC FilteringTRACK WIDTH W:0.03\" PER AMPEREON 1OZ Cu FOIL12VGATER3RGCG•VIA TOGND PLANEPCB Layout ConsiderationsFor proper operation of the LTC4223’s circuit breaker, Kelvin-connection to the sense resistor is strongly rec-ommended. 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 0.5mΩ/square, and voltage drops due to trace resistance add up quickly in high cur-rent applications. In most applications, it will be necessary to use plated-through 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.Design ExampleAs a design example, consider the AMC Hot Swap ap-plication shown earlier in Figure 1 with the power supply requirements given in Table 2.Z1R1C11LTC4223CGN*216158CURRENT FLOWTO SOURCEVIA TOGND PLANE•GND

WGND422312 F12*ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE!

Figure 12. Recommended Layout for Power MOSFET, Sense Resistor and GATE Components on 12V RailThe fi rst 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, ΔVSENSE(CB)(MIN).RSENSE= ΔVSENSE(CB)(MIN)ILOAD(MAX)

=

47.5mV

=6mΩ7.4AA

If a 1% tolerance is assumed for the 6mΩ sense resistor, the minimum and maximum circuit breaker trip current is calculated as follows:Table 2. AMC Power Supply RequirementsSUPPLY VOLTAGE12V3.3VAUXMAXIMUM LOAD CURRENT7.4A150mAMAXIMUM LOAD CAPACITANCE800μF150μFTable 3. MicroTCA Power Supply RequirementsSUPPLY VOLTAGE12V3.3VAUXMAXIMUM LOAD CURRENT7.6A150mAMAXIMUM LOAD CAPACITANCE1600μF150μF422312f18

LTC4223-1/LTC4223-2APPLICATIONS INFORMATION

ITRIP(MIN)=ITRIP(MAX)= ΔVSENSE(CB)(MIN)RSENSE(MAX)RSENSE(MIN)

47.5mmV==7.8A6.06mΩ=

52.5mV

=8.8A

5.94mΩ

CL1•12VOUT2

PAVG=

2•tCHARGE

The inrush current can be limited by using the GATE ca-pacitance (CG) so that the power dissipated in the MOSFET is well within its safe operating area (SOA). For IGATE = 10μA and CL1 = 800μF, we choose CG = 15nF to set the inrush current to 0.5A.IINRUSH=

CL1•IGATE=0.5ACGCL1•12VOUT=19ms

IINRUSH

ΔVSENSE(CB)(MAX)

For proper operation, ITRIP(MIN) must exceed the maximum ce load current with margin, so RSENSE = 6mΩ should suffifor 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 fi lter delay. The worst-case start-up time is calculated using the minimum active current limit value for the auxiliary supply.tSTUP(AUX)= CL2•3.3VAUX150µF•3.3V

=3ms=

165mAIAUX(ACL)(MIN)

tCHARGE=

For a start-up time of 3ms with a 2x safety margin, the TIMER capacitance is calculated as:CT=

2•tSTUP(AUX)123[ms/µF]=

6ms

≅0.05µF

123[ms/µF]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 ΔT = PAVG • Zth where Zth is the thermal impedance.Under this condition, the Si7336ADP datasheet’s Tran-sient Thermal Impedance plot indicates that the junction temperature will increase by 2.4°C using ZthJC = 0.8°C/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 0.1μF • 6[ms/μF] = 600μs for CT = 0.1μF. The maximum short-circuit current is calculated using the maximum analog current limit threshold, ΔVSENSE(ACL)(MAX) and minimum RSENSE value.ISHORT(MAX)= ΔVSENSE(ACL)(MAX)

RSENSE(MIN)

=

mV66m

=11A

5.94mΩ

Considering the tolerances for the TIMER charging rate and capacitance, a value of 0.1μF (±10%) for CT should suffi ce. 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 output-short condition. The fault fi lter delay for the 12V supply is given by 0.1μF • 6[ms/μF] = 600μs 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 ex-ceeded 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:So the maximum power dissipated in the MOSFET is 11A • 12V or 132W for 600μs. The Si7336ADP datasheet’s Tran-sient Thermal Impedance plot indicates that the worse-case increase in junction temperature during the short-circuit condition is 13.2°C using ZthJC = 0.1°C/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.422312f19

LTC4223-1/LTC4223-2TYPICAL APPLICATION

Card Resident Application with 5V Auxiliary SupplyBACKPLANECARDCONNECTORCONNECTOR12VZ1SMAJ13AR110ΩC1100nF12VINR310ΩCGRG15nF47ΩCL11000μFRS4mΩQ1Si7336ADP12V10A12VSENSE12VGATE12VOUT5VR6Z210kSMAJ7.0AR72.7ΩC3100nFR251ΩC2330nFAUXINAUXOUTCL2150μF5VAUX150mAVCCPWRFLTPWRENR810kBD_SELFAULTAUXONLTC4223-112ONENAUXPGOOD12PGOOD5VR410k5VR510k+5V1μFGND12IMON++INVCCLTC1197TIMERCT0.1μFGND–INGND422312 TA02VREFCLKTO SYSTEMCONTROLLER

DOUTCS422312f20

LTC4223-1/LTC4223-2TYPICAL APPLICATION

Card Resident Application with 12V Power Up First Followed by 3.3V AuxiliaryBACKPLANECARDCONNECTORCONNECTOR12VZ1SMAJ13AR110ΩC1100nF12VINR310ΩCGRG15nF47ΩCL11000μFRS4mΩQ1Si7336ADP12V10A12VSENSE12VGATE12VOUT3.3VZ2SMAJ5.0AR72.7ΩC3100nFR251ΩC2330nFAUXINAUXOUTCL2150μF3.3VAUX150mAVCCPWRENR810k3.3VR910k3.3VR510k12ON3.3VLTC4223-1R410kAUXON12PGOODAUXPGOOD3.3VR610kPWRFLTBD_SELGNDQ22N7002K+3.3VFAULTEN12IMON1μF++INVCCLTC1197LTIMERCT0.1μFGND–INGND422312 TA03VREFCLKTO SYSTEMCONTROLLER

DOUTCS422312f21

LTC4223-1/LTC4223-2PACKAGE DESCRIPTION

GN Package16-Lead Plastic SSOP (Narrow .150 Inch)(Reference LTC DWG # 05-08-1641).045 ±.005 .189 – .196*(4.801 – 4.978)161514131211109.254 MIN.150 – .165.229 – .244(5.817 – 6.198) .150 – .157**(3.810 – 3.988).009(0.229)REF.0165 ±.0015.0250 BSC1 .015 ± .004× 45°

(0.38 ± 0.10).0532 – .0688(1.35 – 1.75)2345678.004 – .0098(0.102 – 0.249)RECOMMENDED SOLDER PAD LAYOUT

.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

.008 – .012(0.203 – 0.305)TYP.0250(0.635)BSC

GN16 (SSOP) 0204422312f22

LTC4223-1/LTC4223-2PACKAGE DESCRIPTION

DHD Package16-Lead Plastic DFN (5mm × 4mm)(Reference LTC DWG # 05-08-1707)0.70 ±0.054.50 ±0.053.10 ±0.052.44 ±0.05(2 SIDES)PACKAGEOUTLINE0.25 ± 0.050.50 BSC4.34 ±0.05(2 SIDES)RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

5.00 ±0.10(2 SIDES)R = 0.20TYPR = 0.115TYP9160.40 ± 0.104.00 ±0.10(2 SIDES)PIN 1TOP MARK(SEE NOTE 6)2.44 ± 0.10(2 SIDES)PIN 1NOTCH (DHD16) DFN 050480.200 REF0.75 ±0.054.34 ±0.10(2 SIDES)10.25 ± 0.050.50 BSC0.00 – 0.05BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJGD-2) IN JEDECPACKAGE OUTLINE MO-2292. 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 SIDE5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE

422312fInformation 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 representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.23

LTC4223-1/LTC4223-2TYPICAL APPLICATION

12V/18A Card Resident ApplicationBACKPLANECARDCONNECTORCONNECTOR12VZ1SMAJ13AR110ΩC1100nF12VINR310ΩCGRG15nF47ΩCL11000μFRS2.5mQ1HAT2160H12V18A12VSENSE12VGATE12VOUT3.3VZ2SMAJ5.0AR72.7ΩC3100nFR251ΩC2330nFR910kR810kBD_SELAUXINAUXOUTCL2150μF3.3VAUX150mAVCC3.3VAUXONLTC4223-112ONENAUXPGOOD12PGOODFAULT3..3VR410kR510kR610k+1μFVCCVREF12IMON+INCLKTO

CONTROLLER

LTC1197L+TIMERCT0.1μFGND–INGNDDOUTCS422312 TA04RELATED PARTS

PART NUMBERLTC1421LTC1645DESCRIPTIONDual Channel, Hot Swap ControllerDual Channel, Hot Swap ControllerCOMMENTSOperates from 3V to 12V, Supports –12V, SSOP-24Operates from 3V to 12V, Power Sequencing, SO-8 or SO14Operates from 2.7V to 16.5V, SO-8 or SSOP-16 Operates from 2.7V to 16.5V, Active Current Limiting, SOT23-6Operates from 2.7V to 16.5V, Multifunction Current Control, MSOP-8 or MSOP-10Operates from 2.9V to 15V, I2C Compatible Monitoring, SSOP-16 or QFN-24(4mm × 5mm)Operates from 0V to 6V, MSOP-10 or DFN-12 (4mm × 3mm)Operates from 1V to 13.5V, Multifunction Current Control, SSOP-163.3V, 5V, ±12V Supplies, I2C Compatible Monitoring, SSOP-36 or QFN-38(5mm × 7mm)Fast Active Current Limiting with Drain Accelerated Response, Supplies from –15V, MSOP-8 or MSOP-10LTC1647-1/LTC1647-2/Dual Channel, Hot Swap ControllerLTC1647-3LTC4210LTC4211LTC4215LTC4216LTC4221LTC4245Single Channel, Hot Swap ControllerSingle Channel, Hot Swap ControllerSingle Channel, Hot Swap ControllerSingle Channel, Hot Swap ControllerDual Channel, Hot Swap ControllerMultiple Channel, Hot Swap ControllerLTC4252-1/LTC4252-2/–48V Hot Swap ControllerLTC4252A-1/LTC4252A-2422312f24

Linear Technology CorporationLT 0807 • PRINTED IN USA

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