Datasheet

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LTC4225-1/LTC4225-2

422512f

Typical applicaTion

FeaTures DescripTion

Dual Ideal Diode and

Hot Swap Controller

The LTC

4225 offers ideal diode and Hot Swap™ functions

for two power rails by controlling external series connected

N-channel MOSFETs. MOSFETs acting as ideal diodes

replace two high power Schottky diodes and the associ-

ated heat sinks, saving power and board area. Hot Swap

control MOSFETs allow boards to be safely inserted and

removed from a live backplane by limiting inrush current.

The supply output is also protected against short-circuit

faults with a fast acting current limit and internal timed

circuit breaker.

The LTC4225 regulates the forward voltage drop across

the back-to-back MOSFETs to ensure smooth current

transfer from one supply to the other without oscillation.

The ideal diodes turn on quickly to reduce the load voltage

droop during supply switch-over. If the input supply fails

or is shorted, a fast turn-off minimizes reverse-current

transients.

The LTC4225 allows independent on/off control, and reports

fault and power good status for the supply. The LTC4225-1

features a latch-off circuit breaker, while the LTC4225-2

provides automatic retry after a fault.

µTCA Application

applicaTions

Power Path and Inrush Current Control for

Redundant Supplies

Low Loss Replacement for Power Schottky Diodes

Allows Safe Hot Swapping from a Live Backplane

2.9V to 18V Operating Range

Controls N-Channel MOSFETs

Limits Peak Fault Current in ≤1µs

0.5µs Turn-On and Reverse Turn-Off Time

Adjustable Current Limit with Circuit Breaker

Smooth Switchover without Oscillation

Adjustable Current Limit Fault Delay

Fault and Power Status Output

LTC4225-1: Latch Off After Fault

LTC4225-2: Automatic Retry After Fault

24-Lead 4mm × 5mm QFN and SSOP Packages

Redundant Power Supplies

Supply Holdup

MicroTCA Systems and Servers

Telecom Networks

Power Prioritizer

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

CPO1

ON1

137k

12V

ON2

INTV

GND

0.1µF

47nF 47nF

12V

7.6A

PLUG-IN

CARD 1

PLUG-IN

CARD 2

BACKPLANE

422512 TA01a

IN1 SENSE1 DGATE1

Si7336ADP

LTC4225

0.004Ω

Si7336ADP

0.004Ω

Si7336ADP

HGATE1 OUT1

CPO2 IN2 SENSE2 DGATE2 HGATE2 OUT2

FAULT1

PWRGD1

EN1

TMR1

TMR2

EN2

PWRGD2

FAULT2

20k

137k

12V

7.6A

Power Dissipation vs Load Current

LOAD CURRENT (A)

POWER DISSIPATION (W)

0.5

1.0

1.5

2.0

2.5

3.0

2 4 6 8

422512 TA01

DIODE

(SBG1025L)

MOSFET

(Si7336ADP)

POWER SAVED

Summary of content (24 pages)

PAGE 1
LTC4225-1/LTC4225-2 Dual Ideal Diode and Hot Swap Controller Features n n n n n n n n n n n n n n Description Power Path and Inrush Current Control for Redundant Supplies Low Loss Replacement for Power Schottky Diodes Allows Safe Hot Swapping from a Live Backplane 2.9V to 18V Operating Range Controls N-Channel MOSFETs Limits Peak Fault Current in ≤1µs 0.
PAGE 2
LTC4225-1/LTC4225-2 Absolute Maximum Ratings (Notes 1, 2) Supply Voltages IN1, IN2................................................... –0.3V to 24V INTVCC...................................................... –0.3V to 7V Input Voltages ON1, ON2, EN1, EN2............................... –0.3V to 24V TMR1, TMR2..........................–0.3V to INTVCC + 0.3V SENSE1, SENSE2.................................... –0.3V to 24V Output Voltages FAULT1, FAULT2, PWRGD1, PWRGD2...... –0.3V to 24V CPO1, CPO2 (Note 3)......
PAGE 3
LTC4225-1/LTC4225-2 Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4225CUFD-1#PBF LTC4225CUFD-1#TRPBF 42251 24-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4225CUFD-2#PBF LTC4225CUFD-2#TRPBF 42252 24-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4225IUFD-1#PBF LTC4225IUFD-1#TRPBF 42251 24-Lead (4mm × 5mm) Plastic QFN –40°C to 85°C LTC4225IUFD-2#PBF LTC4225IUFD-2#TRPBF 42252 24-Lead (4mm × 5mm) Plastic QFN –40°C to 85°C LTC4225CGN
PAGE 4
LTC4225-1/LTC4225-2 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, unless otherwise noted.
PAGE 5
LTC4225-1/LTC4225-2 Typical Performance Characteristics TA = 25°C, VIN = 12V, unless otherwise noted. IN Supply Current vs Voltage 6 4 INTVCC Load Regulation CPO Voltage vs Current 12 VIN = 12V 5 10 VCPO – VIN (∆VCPO) (V) 3 INTVCC (V) IIN (mA) 4 2 VIN = 3.3V 3 2 1 1 0 0 3 6 9 VIN (V) 15 12 0 18 0 –2 –4 –6 ILOAD (mA) GATE DRIVE (∆VHGATE) (V) VDGATE – VIN (∆VDGATE) (V) VIN = 2.9V 2 0 –2 –20 –40 –80 –60 IDGATE (µA) –100 VIN = 2.9V 6 0.5 4 0 0 –2 –4 –6 –8 –10 –0.
PAGE 6
LTC4225-1/LTC4225-2 Typical Performance Characteristics TA = 25°C, VIN = 12V, unless otherwise noted. HGATE Pull-Up Current vs Temperature TMR Pull-Up Current vs Temperature –103 –11.0 0.8 –10.5 OUTPUT LOW VOLTAGE (V) –102 TMR PULL-UP CURRENT (µA) HGATE PULL-UP CURRENT (µA) PWRGD, FAULT Output Low Voltage vs Current –101 –10.0 –100 –9.5 –9.0 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 –99 0.6 0.4 0.
PAGE 7
LTC4225-1/LTC4225-2 Pin Functions INTVCC: Internal 5V Supply Decoupling Output. This pin must have a 0.1µF or larger capacitor. An external load of less than 500µA can be connected at this pin. ON1, ON2: On Control Input. A rising edge above 1.235V turns on the external Hot Swap MOSFET and a falling edge below 1.155V turns it off. Connect this pin to an external resistive divider from IN to monitor the supply undervoltage condition. Pulling the ON pin below 0.6V resets the electronic circuit breaker.
PAGE 8
LTC4225-1/LTC4225-2 Block Diagram IN1 65mV HGATE1 + A1 – SENSE2 50mV +– + ECB1 – + ECB2 – CHARGE PUMP 1 CHARGE PUMP 2 INTVCC OUT1 5V LDO +– –+ 25mV 25mV 2.2V + – 1.9V 1.235V ON1 INTVCC 0.6V 10µA + – CP5 GATE DRIVER 2 + GA2 – – + – + CP2 OUT2 INTVCC INTVCC UV3 UV2 CP3 HGATE2 ON HGATE1 ON FAULT1 RESET CP4 FAULT2 RESET CARD1 PRESENCE DETECT IN2 1.235V 1.9V ON2 INTVCC 0.6V CP6 CARD2 PRESENCE DETECT INTVCC TMR1 0.
PAGE 9
LTC4225-1/LTC4225-2 Operation The LTC4225 functions as an ideal diode with inrush current limiting and overcurrent protection by controlling two external back-to-back N-channel MOSFETs (MD and MH) on a supply path. This allows boards to be safely inserted and removed in systems with a backplane powered by redundant supplies, such as µTCA applications. The LTC4225 has two separate ideal diode and Hot Swap controllers, each providing independent control for the two input supplies.
PAGE 10
LTC4225-1/LTC4225-2 Applications Information circuit selects the highest of the supplies at the IN and OUT pins to power the device through the LDO. The diode-OR scheme permits the device’s power to be temporarily kept alive by the OUT load capacitance when the IN supplies have collapsed or shut off. High availability systems often employ parallel-connected power supplies or battery feeds to achieve redundancy and enhance system reliability.
PAGE 11
LTC4225-1/LTC4225-2 Applications Information During a normal power-up, the ideal diode MOSFET turns on first. As soon as the internally generated supply, INTVCC, rises above its 2.2V undervoltage lockout threshold, the internal charge pump is allowed to charge up the CPO pins. Because the Hot Swap MOSFET is turned off at power-up, OUT remains low. As a result, the ideal diode gate drive amplifier senses a large forward drop between the IN and OUT pins, causing it to pull up DGATE to the CPO pin voltage.
PAGE 12
LTC4225-1/LTC4225-2 Applications Information Board Presence Detect with EN If ON is high when the EN pin goes low, indicating a board presence, the LTC4225 initiates a 100ms timing cycle for contact debounce. Upon board insertion, any bounces on the EN pin restart the timing cycle. When the 100ms timing cycle is done, the internal fault latches are cleared. If the EN pin remains low at the end of the timing cycle, HGATE is charged up with a 10µA current source to turn on the Hot Swap MOSFET.
PAGE 13
LTC4225-1/LTC4225-2 Applications Information Active Current Loop Stability The active current loop on the HGATE pin is compensated by the parasitic gate capacitance of the external N-channel MOSFET. No further compensation components are normally required. In the case when a MOSFET with CISS ≤ 2nF is chosen, an RHG and CHG compensation network connected at the HGATE pin may be required. The value of CHG is selected based on the inrush current allowed for the output load capacitance.
PAGE 14
LTC4225-1/LTC4225-2 Applications Information If both IN supplies fall until the internally generated supply, INTVCC, drops below its 2.2V UVLO threshold, all the MOSFETs are turned off and the fault latches are cleared. Operation resumes from a fresh start-up cycle when the input supplies are restored and INTVCC exceeds its UVLO threshold. TMR 1V/DIV FAULT 10V/DIV HGATE 5V/DIV ILOAD 20A/DIV 50ms/DIV 422512 F06 Figure 6.
PAGE 15
LTC4225-1/LTC4225-2 Applications Information MOSFET Selection The LTC4225 drives N-channel MOSFETs to conduct the load current. The important features of the MOSFETs are on-resistance, RDS(ON), the maximum drain-source voltage, BVDSS, and the threshold voltage. The gate drive for the ideal diode MOSFET and Hot Swap MOSFET is guaranteed to be greater than 5V and 4.8V respectively when the supply voltages at IN1 and IN2 are between 2.9V and 7V.
PAGE 16
LTC4225-1/LTC4225-2 Applications Information Next, verify that the thermal ratings of the selected MOSFET, Si7336ADP, are not exceeded during power-up or an output short.
PAGE 17
LTC4225-1/LTC4225-2 Applications Information Connect the IN and OUT pin traces as close as possible to the MOSFETs’ terminals. Keep the traces to the MOSFETs wide and short to minimize resistive losses. The PCB traces associated with the power path through the MOSFETs should have low resistance. The suggested trace width for 1oz copper foil is 0.03" for each ampere of DC current to keep PCB trace resistance, voltage drop and temperature rise to a minimum.
PAGE 18
LTC4225-1/LTC4225-2 Applications Information Power Prioritizer Additional Applications Figure 8 shows an application where either of two supplies is passed to the output on the basis of priority, rather than simply allowing the highest voltage to prevail. The 5V primary supply (INPUT 1) is passed to the output whenever it is available; power is drawn from the 12V backup supply (INPUT 2) only when the primary supply is unavailable. As long as INPUT 1 is above the 4.
PAGE 19
LTC4225-1/LTC4225-2 Applications Information RS1 0.006Ω BULK SUPPLY BYPASS CAPACITOR RH1 10Ω CPO1 PWREN2 IN1 SENSE1 HGATE1 DGATE1 INTVCC LTC4225 GND IN2 SENSE2 HGATE2 CCP2 0.1µF OUT1 FAULT1 PWRGD1 EN1 TMR1 TMR2 CT2 47nF CL1 1000µF PLUG-IN CARD 2 CT1 47nF EN2 PWRGD2 FAULT2 DGATE2 OUT2 ON2 CPO2 VIN2 12V + RHG1 47Ω CHG1 15nF ON1 C1 0.1µF 12V 5A ZH1 ZD1 CCP1 0.
PAGE 20
LTC4225-1/LTC4225-2 Applications Information RS1 0.006Ω VIN1 12V Z1 SMAJ13A R1 20k C1 0.1µF R3 20k RH1 10Ω CCP1 0.1µF CPO1 EN1 ON1 CF1 0.1µF CF2 0.1µF R4 137k IN1 SENSE1 DGATE1 BACKPLANE CONNECTOR CARD CONNECTOR Z2 SMAJ13A RHG1 47Ω CHG1 15nF HGATE1 OUT1 12V 5A CL 1000µF VIN1 R5 100k R6 100k FAULT1 PWRGD1 INTVCC TMR1 TMR2 LTC4225 GND PWRGD2 FAULT2 ON2 EN2 CPO2 IN2 SENSE2 DGATE2 CCP2 0.1µF VIN2 12V MH1 SiR466DP + RSNUB1 10Ω CSNUB1 0.1µF R2 137k MD1 SiR466DP RS2 RSNUB2 0.
PAGE 21
LTC4225-1/LTC4225-2 Applications Information POWER MODULE #1 BACKPLANE 12V IN1 SENSE1 DGATE1 AMC #1 HGATE1 OUT1 LTC4225* IN2 SENSE2 DGATE2 HGATE2 OUT2 12V AMC #2 • • 8x • • (12 AMCs, 2 CUs, 2 MCHs) • 16x • 12V MCH #1 IN1 SENSE1 DGATE1 HGATE1 OUT1 LTC4225* IN2 SENSE2 DGATE2 HGATE2 OUT2 12V MCH #2 POWER MODULE #2 12V IN1 SENSE1 DGATE1 HGATE1 OUT1 LTC4225* IN2 SENSE2 DGATE2 HGATE2 OUT2 12V • • 8x • 12V IN1 SENSE1 DGATE1 HGATE1 OUT1 LTC4225* IN2 SENSE2 DGATE2 HGATE2 OUT2 12V 422
PAGE 22
LTC4225-1/LTC4225-2 Package Description UFD Package 24-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1696 Rev A) 0.70 ±0.05 4.50 ± 0.05 3.10 ± 0.05 2.00 REF 2.65 ± 0.05 3.65 ± 0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 3.00 REF 4.10 ± 0.05 5.50 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ± 0.10 (2 SIDES) R = 0.05 TYP 2.00 REF R = 0.115 TYP 23 0.75 ± 0.05 PIN 1 NOTCH R = 0.20 OR C = 0.35 24 0.40 ± 0.
PAGE 23
LTC4225-1/LTC4225-2 Package Description GN Package 24-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .337 – .344* (8.560 – 8.738) 24 23 22 21 20 19 18 17 16 15 1413 .045 ±.005 .229 – .244 (5.817 – 6.198) .254 MIN .033 (0.838) REF .150 – .157** (3.810 – 3.988) .150 – .165 1 .0165 ±.0015 2 3 4 5 6 7 8 9 10 11 12 .0250 BSC RECOMMENDED SOLDER PAD LAYOUT .015 ± .004 × 45° (0.38 ± 0.10) .0075 – .0098 (0.19 – 0.25) .0532 – .0688 (1.35 – 1.75) .004 – .0098 (0.102 – 0.
PAGE 24
LTC4225-1/LTC4225-2 Typical Application Plug-In Card Diode-OR Application with Hot Swap First Followed by Ideal Diode Control RS1 0.006Ω VIN1 5V Z1 SMAJ7A PWREN + CCP1 0.1µF CPO1 EN1 ON1 R1 10k C1 0.1µF MH1 MD1 Si7790DP Si7790DP IN1 SENSE1 HGATE1 DGATE1 CL 100µF 5V 5A OUT1 FAULT1 PWRGD1 INTVCC TMR1 TMR2 LTC4225 GND CT2 0.1µF CT1 0.1µF PWRGD2 FAULT2 ON2 EN2 CPO2 IN2 SENSE2 HGATE2 DGATE2 OUT2 CCP2 0.1µF VIN2 5V BACKPLANE CONNECTOR Z2 SMAJ7A CARD CONNECTOR RS2 0.