Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - hot swap controller Multi-purpose QFN 20 Surface-mount

LTC4227

422712fa

For more information www.linear.com/LTC4227

Typical applicaTion

FeaTures DescripTion

Dual Ideal Diode and

Single Hot Swap Controller

The LT C

4227 offers ideal diode-OR and Hot Swap™

functions for two power rails by controlling external N-

channel MOSFETs. MOSFETs acting as ideal diodes replace

two high power Schottky diodes and the associated heat

sinks, saving power and board area. A Hot Swap control

MOSFET allows a board 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 LTC4227 regulates the forward voltage drop across

the 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 switchover. If the input supply fails or is shorted,

a fast turn-off minimizes reverse-current transients.

The LTC4227 allows turn-on/off control, and reports fault

and power good status for the supply.

PART OVERCURRENT FAULT START-UP DELAY

LTC4227-1 LATCH OFF 100ms

LTC4227-2 RETRY 100ms

LTC4227-3 LATCH OFF 1.6ms

LTC4227-4 RETRY 1.6ms

Diode-OR with Hot Swap 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 Ideal Diode 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

20-Lead 4mm × 5mm QFN and 16-Lead SSOP Packages

Redundant Power Supplies and Supply Holdup

Computer Systems and Servers

Telecom Networks

L, LT , LT C , LT M , 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.

BACKPLANE

CONNECTOR

12V

CARD

CONNECTOR

CPO1

D2ON

PWRGD

FAULT

137k

100µF

12V

7.6A

20k

INTV

CC GND

IN1 DGATE1 DGATE2

LTC4227

4227 TA01a

SiR462DP Si7336ADP0.006Ω

HGATE OUTSENSE

SENSE

–

CPO2

0.1µF

IN2

0.1µF

SiR462DP

0.1µF0.1µF

TMR

Smooth Supply Switchover

200ns/DIV

IN2

2A/DIV

IN1

2A/DIV

IN2

1V/DIV

IN1

1V/DIV

4227 TA01b

Summary of content (22 pages)

PAGE 1
LTC4227 Dual Ideal Diode and Single Hot Swap Controller Features 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
LTC4227 Absolute Maximum Ratings (Notes 1, 2) Supply Voltages IN1, IN2................................................... –0.3V to 24V INTVCC...................................................... –0.3V to 7V Input Voltages ON, EN, D2ON ........................................ –0.3V to 24V TMR........................................–0.3V to INTVCC + 0.3V SENSE+, SENSE–.................................... –0.3V to 24V Output Voltages FAULT, PWRGD....................................... –0.
PAGE 3
LTC4227 Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC4227CUFD-1#PBF LTC4227CUFD-1#TRPBF 42271 20-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4227CUFD-2#PBF LTC4227CUFD-2#TRPBF 42272 20-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4227CUFD-3#PBF LTC4227CUFD-3#TRPBF 42273 20-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4227CUFD-4#PBF LTC4227CUFD-4#TRPBF 42274 20-Lead (4mm × 5mm) Plastic QFN 0°C to 70°C LTC4227IUFD-1#PBF LTC4227
PAGE 4
LTC4227 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. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Hot Swap Control ∆VSENSE(CB) Circuit Breaker Trip Sense Voltage (VSENSE+ – VSENSE–) l 47.5 50 52.
PAGE 5
LTC4227 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. SYMBOL PARAMETER CONDITIONS VOH Output High Voltage (FAULT, PWRGD) I = –1µA l INTVCC – 1 INTVCC – 0.5 MIN TYP IOH Input Leakage Current (FAULT, PWRGD) V = 18V l IPU Output Pull-Up Current (FAULT, PWRGD) V = 1.
PAGE 6
LTC4227 Typical Performance Characteristics TA = 25°C, VIN = 12V, unless otherwise noted. Hot Swap Gate Voltage vs IN Voltage 2.0 52 VIN = 12V CIRCUIT BREAKER TRIP VOLTAGE (mV) VOUT = VIN 1.6 12 1.2 10 IOUT (mA) GATE DRIVE (∆VHGATE) (V) 14 Circuit Breaker Trip Voltage vs Temperature OUT Current vs Voltage 8 0.8 0.4 6 4 0 0 3 6 9 VIN (V) 12 15 –0.
PAGE 7
LTC4227 Pin Functions CPO1, CPO2: Charge Pump Output. Connect a capacitor from CPO1 or CPO2 to the corresponding IN1 or IN2 pin. The value of this capacitor is approximately 10× the gate capacitance (CISS) of the external MOSFET for ideal diode control. The charge stored on this capacitor is used to pull up the gate during a fast turn-on. Leave this pin open if fast turn-on is not needed. DGATE1, DGATE2: Ideal Diode MOSFET Gate Drive Output.
PAGE 8
LTC4227 Pin Functions limit circuit controls HGATE to limit the voltage between SENSE+ and SENSE– to 65mV. A circuit breaker trips when the sense voltage exceeds 50mV for more than a fault filter delay configured at the TMR pin. TMR: Timer Capacitor Terminal. Connect a capacitor between this pin and ground to set a 12ms/µF duration for current limit before the external Hot Swap MOSFET is turned off. The duration of the off-time is 617ms/µF, resulting in a 2% duty cycle.
PAGE 9
LTC4227 Operation The LTC4227 functions as an input supply diode-OR with inrush current limiting and overcurrent protection by controlling the external N-channel MOSFETs (MD1, MD2 and MH) on a supply path. This allows boards to be safely inserted and removed in systems with a backplane powered by redundant supplies. The LTC4227 has a single Hot Swap controller and two separate ideal diode controllers, each providing independent control for the two input supplies.
PAGE 10
LTC4227 Applications Information High availability systems often employ parallel-connected power supplies or battery feeds to achieve redundancy and enhance system reliability. Power ORing diodes are commonly used to connect these supplies at the point of load, but at the expense of power loss due to significant diode forward voltage drop.
PAGE 11
LTC4227 Applications Information During a normal power-up, the ideal diode MOSFETs turn 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 ideal diode MOSFETs are connected in parallel as a diode-OR, the SENSE+ pin voltage approaches the highest of the supplies at the IN1 and IN2 pins.
PAGE 12
LTC4227 Applications Information Board Presence Detect with EN If ON is high when the EN pin goes low, indicating a board presence, the LTC4227 initiates a debounce timing cycle for contact debounce. Upon board insertion, any bounces on the EN pin restart the timing cycle. When the debounce 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
LTC4227 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
LTC4227 Applications Information There is a 10µs glitch filter on the ON pin to reject supply glitches. By placing a filter capacitor, CF , with the resistive divider at the ON pin, the glitch filter delay is further extended by the RC time constant to prevent any false fault. TMR 1V/DIV FAULT 10V/DIV HGATE 5V/DIV Power Good Monitor ILOAD 10A/DIV 100ms/DIV 4227 F06 Figure 6.
PAGE 15
LTC4227 Applications Information to be greater than 10V. The gate drive is limited to not more than 14V. This allows the use of logic-level threshold N-channel MOSFETs and standard N-channel MOSFETs above 7V. An external Zener diode can be used to clamp the potential from the MOSFET ’s gate to source if the rated breakdown voltage is less than 14V. The maximum allowable drain-source voltage, BVDSS, must be higher than the supply voltages as the full supply voltage can appear across the MOSFET.
PAGE 16
LTC4227 Applications Information For CL = 680µF, the time it takes to charge up CL is calculated as: C •V 680µF • 12V tCHARGE = L IN = = 16ms IINRUSH 0.5A 21.3°C using ZthJC = 0.15°C/W (single pulse). Choosing CT = 0.1µF will not cause the maximum junction temperature of the MOSFET to be exceeded. The SOA curves of the Si7336ADP provide for 6A at 30V (180W) for 10ms. This also satisfies the requirement. The inrush current is set to 0.5A by adding capacitance, CHG, at the gate of the Hot Swap MOSFET.
PAGE 17
LTC4227 Applications Information the diode-OR output to be switched from the main 3.3V supply at IN1 to the auxiliary 3.3V supply at IN2. This configuration permits the load to be supplied from a lower IN1 supply as compared to IN2 until IN1 falls below the MD2 turn-on threshold. The threshold value used should not allow the IN1 supply to be operated at more than one diode voltage below IN2. Otherwise, MD2 conducts through the MOSFET ’s body diode.
PAGE 18
LTC4227 Applications Information MD1 SiR462DP VMAIN 3.3V Z1 SMAJ7A VAUX 3.3V CCP1 0.1µF Z2 SMAJ7A R1 20k SENSE– HGATE OUT LTC4227 D2ON INTVCC R3 10k CL 100µF 3.3V 5A R4 10k FAULT PWRGD ON CF1 0.1µF R6 28.7k R5 20k MH Si7336ADP + IN2 DGATE2 SENSE+ IN1 DGATE1 CPO2 CPO1 EN CARD CONNECTOR RS 0.008Ω CCP2 0.1µF R2 22.1k BACKPLANE CONNECTOR MD2 SiR462DP TMR GND CT 0.1µF C1 0.1µF 4227 F08 CF2 10nF Figure 8.
PAGE 19
LTC4227 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UFD Package 20-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1711 Rev B) 0.70 ±0.05 4.50 ±0.05 1.50 REF 3.10 ±0.05 2.65 ±0.05 3.65 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 2.50 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) 0.75 ±0.05 PIN 1 NOTCH R = 0.20 OR C = 0.35 1.
PAGE 20
LTC4227 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 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 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) .0532 – .
PAGE 21
LTC4227 Revision History REV DATE DESCRIPTION A 07/13 Added LTC4227-3, LTC4227-4 information PAGE NUMBER Multiple Added specification: VD2ON(L,TH), D2ON Pin Low Threshold 4 Changed ΔVD2ON(HYST) typical value from 80mV to 90mV 4 Added two curves to G01; Added Diode and Hot Swap Gate Voltage vs IN Voltage graphs 5, 6 422712fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 22
LTC4227 Typical Application Backplane Resident Diode-OR Application with Inrush Current Limiting at 12V Supply Inputs MD1 Si7336ADP VIN1 12V BULK SUPPLY BYPASS CAPACITOR VIN2 12V CCP1 0.1µF MD2 Si7336ADP RS 0.008Ω MH Si7336ADP + BULK SUPPLY BYPASS CAPACITOR RH 10Ω CCP2 0.1µF 12V 5A CL 1000µF RHG 47Ω CHG 15nF R2 137k R1 20k CPO1 CF 10nF IN1 DGATE1 CPO2 IN2 DGATE2 SENSE+ SENSE– HGATE LTC4227 INTVCC D2ON OUT FAULT PWRGD ON GND C1 0.1µF EN TMR CT 0.