Datasheet

ManualsBrandsLinear Technology ManualsHot Swap ControllersSurge Stopper 4 ... 80V DFN

LT4356-1/LT4356-2

4356fb

For more information www.linear.com/LT4356-1

ApplicAtions

FeAtures Description

Surge Stopper

The LT

4356 surge stopper protects loads from high voltage

transients. It regulates the output during an overvoltage

event, such as load dump in automobiles, by controlling

the gate of an external N-channel MOSFET. The output is

limited to a safe value thereby allowing the loads to con

tinue functioning. The LT4356 also monitors the voltage

drop between the V

and SNS pins to protect against

overcurrent faults. An internal ampliﬁer limits the current

sense voltage to 50mV. In either fault condition, a timer

is started inversely proportional to MOSFET stress. If the

timer expires, the F LT pin pulls low to warn of an impend

ing power down. If the condition persists, the MOSFET is

turned off. After a cool down period, the GATE pin pulls

up turning on the MOSFET again.

The auxiliary ampliﬁer may be used as a voltage detection

comparator or as a linear regulator controller driving an

external PNP pass transistor.

Back-to-back FETs can be used in lieu of a Schottky diode

for reverse input protection, reducing voltage drop and

power loss. A shutdown pin reduces the quiescent current

to less than 7µA for the LT4356-1 during shutdown. The

LT4356-2 differs from the LT4356-1 during shutdown by

reducing the quiescent current to 60µA and keeping alive

the auxiliary ampliﬁer for uses such as an undervoltage

lockout or always-on regulator.

Automotive/Avionic Surge Protection

Hot Swap/Live Insertion

High Side Switch for Battery Powered Systems

Intrinsic Safety Applications

Stops High Voltage Surges

Adjustable Output Clamp Voltage

Overcurrent Protection

Wide Operation Range: 4V to 80V

Reverse Input Protection to –60V

Low 7µA Shutdown Current, LT4356-1

Adjustable Fault Timer

Controls N-channel MOSFET

Shutdown Pin Withstands –60V to 100V

Fault Output Indication

Guaranteed Operation to 125°C

Auxiliary Ampliﬁer for Level Detection Comparator or

Linear Regulator Controller

Available in (4mm × 3mm) 12-Pin DFN,

10-Pin MSOP or 16-Pin SO Packages

4A, 12V Overvoltage Output Regulator Overvoltage Protector Regulates Output at

27V During Transient

0.1µF

10Ω

10mΩ

IRLR2908

12V

4356 TA01

LT4356DE

GND TMR

OUTGATESNS

SHDN

OUT

FAULT

OUT

FLTUNDERVOLTAGE

DC-DC

CONVERTER

GND

SHDN

4.99k

383k

100k

102k

100ms/DIV

4356 TA01b

20V/DIV

OUT

20V/DIV

80V INPUT SURGE

TMR

= 6.8µF

LOAD

= 500mA

27V ADJUSTABLE CLAMP

12V

typicAl ApplicAtion

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No

SENSE

and ThinSOT are trademarks of Analog Devices, Inc. All other trademarks are the

property of their respective owners.

Downloaded from Arrow.com.

Summary of content (26 pages)

PAGE 1
LT4356-1/LT4356-2 Surge Stopper Features n n n n n n n n n n n n n Description Stops High Voltage Surges Adjustable Output Clamp Voltage Overcurrent Protection Wide Operation Range: 4V to 80V Reverse Input Protection to –60V Low 7µA Shutdown Current, LT4356-1 Adjustable Fault Timer Controls N-channel MOSFET Shutdown Pin Withstands –60V to 100V Fault Output Indication Guaranteed Operation to 125°C Auxiliary Amplifier for Level Detection Comparator or Linear Regulator Controller Available in (4mm × 3mm) 12
PAGE 2
LT4356-1/LT4356-2 Absolute Maximum Ratings (Notes 1 and 2) VCC, SHDN................................................. –60V to 100V SNS.............................. VCC – 30V or –60V to VCC + 0.3V OUT, AOUT, FLT, EN...................................... –0.3V to 80V GATE (Note 3)..................................–0.3V to VOUT + 10V FB, TMR, IN+................................................. –0.3V to 6V AOUT, EN, FLT, IN+...................................................
PAGE 3
LT4356-1/LT4356-2 Order Information LEAD FREE FINISH TAPE AND REEL http://www.linear.
PAGE 4
LT4356-1/LT4356-2 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V unless otherwise noted.
PAGE 5
LT4356-1/LT4356-2 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VSHDN(FLT) SHDN Pin Float Voltage SHDN Pin Current ISHDN Overcurrent Turn Off Delay Time tOFF(OC) Overvoltage Turn Off Delay Time tOFF(OV) MIN TYP MAX 0.6 –1 2.1 –8 4 V µA µs 1 µs VCC = 12V to 48V VSHDN = 0V l GATE From High to Low, ΔVSNS = 0 → 120mV l 1.
PAGE 6
LT4356-1/LT4356-2 Typical Performance Characteristics Specifications are at VCC = 12V, TA = 25°C unless otherwise noted.
PAGE 7
LT4356-1/LT4356-2 Typical Performance Characteristics Specifications are at VCC = 12V, TA = 25°C unless otherwise noted. OVERVOLTAGE, EARLY WARNING PERIOD 12 VFB = 1.5V VTMR = 1.3V 10 ITMR (µA) ITMR (µA) 200 160 120 6 4 40 2 10 20 30 40 50 VCC – VOUT (V) 60 70 2.0 8 80 0 80 0.5 0 10 4356 G13 20 30 40 50 VCC (V) 60 –25 0 25 50 75 TEMPERATURE (°C) 100 125 4356 G15 Overvoltage Turn-Off Time vs Temperature 500 AOUT OVERVOLTAGE CONDITION VFB = 1.5V 400 3.0 FLT 2.
PAGE 8
LT4356-1/LT4356-2 Pin Functions AOUT (DFN and SO Packages Only): Amplifier Output. Open collector output of the auxiliary amplifier. It is capable of sinking up to 2mA from 80V. The negative input of the amplifier is internally connected to a 1.25V reference. OUT: Output Voltage Sense Input. This pin senses the voltage at the source of the N-channel MOSFET and sets the fault timer current. When the OUT pin voltage reaches 0.7V away from VCC, the EN pin goes high impedance.
PAGE 9
LT4356-1/LT4356-2 Block Diagram VCC GATE + – 14V CHARGE PUMP + OUT FB – + 50mV SNS VA IA 1.25V – SHDN FLT AOUT OC 1.25V AUXILIARY AMPLIFIER SHDN RESTART OUT – + 1.35V + 0.5V EN CONTROL LOGIC GATEOFF IN+ OV FLT – VCC ITMR + – + 2µA 1.25V TMR – GND 4356 BD 4356fb For more information www.linear.com/LT4356-1 Downloaded from Arrow.com.
PAGE 10
LT4356-1/LT4356-2 Operation Some power systems must cope with high voltage surges of short duration such as those in automobiles. Load circuitry must be protected from these transients, yet high availability systems must continue operating during these events. The potential at the TMR pin starts decreasing as soon as the overvoltage condition disappears. When the voltage at the TMR pin reaches 0.5V the GATE pin begins rising, turning on the MOSFET. The FLT pin will then go to a high impedance state.
PAGE 11
LT4356-1/LT4356-2 Applications Information The LT4356 can limit the voltage and current to the load circuitry during supply transients or overcurrent events. The total fault timer period should be set to ride through short overvoltage transients while not causing damage to the pass transistor. The selection of this N-channel MOSFET pass transistor is critical for this application.
PAGE 12
LT4356-1/LT4356-2 Applications Information Fault Timer Current The timer current starts at around 2µA with 0.5V or less of VDS, increasing linearly to 50µA with 75V of VDS during an overvoltage fault (Figure 1). During an overcurrent fault, it starts at 4µA with 0.5V or less of VDS but increases to 260µA with 80V across the MOSFET (Figure 2). This arrangement allows the pass transistor to turn off faster during an overcurrent event, since more power is dissipated during this condition.
PAGE 13
LT4356-1/LT4356-2 Applications Information This fixed early warning period allows the systems to perform necessary backup or house-keeping functions before the power supply is cut off. After VTMR crosses the 1.35V threshold, the pass transistor turns off immediately. Note that during an overcurrent event, the timer current is not reduced to 5µA after VTMR has reached 1.25V threshold, since it would lengthen the overall fault timer period and cause more stress on the power MOSFET.
PAGE 14
LT4356-1/LT4356-2 Applications Information MOSFET stress is the result of power dissipated within the device. For long duration surges of 100ms or more, stress is increasingly dominated by heat transfer; this is a matter of device packaging and mounting, and heatsink thermal mass. This is analyzed by simulation, using the MOSFET thermal model. For short duration transients of less than 100ms, MOSFET survival is increasingly a matter of safe operating area (SOA), an intrinsic property of the MOSFET.
PAGE 15
LT4356-1/LT4356-2 Applications Information The LTC4356 does not need extra compensation components at the GATE pin for stability during an overvoltage or overcurrent event. With transient input voltage step faster than 5V/µs, a gate capacitor, C1, to ground is needed to prevent self enhancement of the N-channel MOSFET. The extra gate capacitance slows down the turn off time during fault conditions and may allow excessive current during an output short event.
PAGE 16
LT4356-1/LT4356-2 Applications Information RSNS 10mΩ VIN 12V Q2 Si4435 Q1 IRLR2908 VOUT 12V, 3A CLAMPED AT 16V D1 1N5245 15V D2* SMAJ58CA R3 10Ω R6 10k 5 SNS 6 R1 59k 3 OUT 4 GATE FB VCC 2 R2 4.99k 7 11 12 LT4356S SHDN AOUT IN+ FLT GND 10 *DIODES INC. EN TMR 1 8 9 4356 F08 CTMR 0.1µF Figure 8.
PAGE 17
LT4356-1/LT4356-2 Applications Information Layout Considerations Next calculate the sense resistor, RSNS, value: To achieve accurate current sensing, Kelvin connection to the current sense resistor (RSNS in Figure 9) is recommended. The minimum trace width for 1oz copper foil is 0.02" per amp to ensure the trace stays at a reasonable temperature. 0.03" per amp or wider is recommended. Note that 1oz copper exhibits a sheet resistance of about 530µΩ/square.
PAGE 18
LT4356-1/LT4356-2 Typical Applications Wide Input Range 5V to 28V Hot Swap with Undervoltage Lockout RSNS 20mΩ VIN Q1 SUD50N03-10 R6 118k VOUT 100µF R3 10Ω C1 47nF SNS VCC GATE OUT FB SHDN AOUT IN+ LT4356DE-1 R7 49.9k FLT GND EN TMR 4356 TA02 CTMR 1µF 24V Overvoltage Regulator Withstands 150V at VIN VIN 24V Q1 IRF640 R9 1k 1W R3 10Ω 4 GATE 5 SNS 6 D2* SMAT70A R1 118k 3 OUT FB VCC 2 R2 4.99k 7 8 9 LT4356DE SHDN FLT EN GND 10 *DIODES INC. VOUT CLAMPED AT 32V TMR 1 CTMR 0.
PAGE 19
LT4356-1/LT4356-2 Typical Applications Overvoltage Regulator with Undervoltage Lockout RSNS 20mΩ VIN D2* SMAJ58A R6 280k Q1 IRLR2908 R4 1M R3 10Ω SNS VCC R5 1M VOUT CLAMPED AT 16V GATE R1 59k OUT FB SHDN R2 4.99k AOUT IN+ UV RISING = 5.04V LT4356DE-2 R7 100k FLT GND *DIODES INC. EN TMR 4356 TA04 CTMR 0.1µF Overvoltage Regulator with Low Battery Detection and Output Keep Alive During Shutdown 1k 0.
PAGE 20
LT4356-1/LT4356-2 Typical Applications 2.5A, 48V Hot Swap with Overvoltage Output Regulation at 72V and UV Shutdown at 35V RSNS 15mΩ VIN 48V Q1 FDB3632 D2* SMAT70A R4 140k R3 10Ω VOUT 48V 2.5A R6 100k CL 300µF C1 6.8nF 6 VCC D1 1N4714 BV = 33V 7 5 4 SNS GATE 3 OUT IN SHDN + 12 R5 4.02k R8 47k LT4356DE 8 R7 1M FB R1 226k 2 R2 4.02k FLT 9 EN GND *DIODES INC. AOUT TMR 10 1 11 PWRGD 4356 TA06 CTMR 0.1µF 2.
PAGE 21
LT4356-1/LT4356-2 Typical Applications Overvoltage Regulator with Reverse Input Protection Up to –80V RSNS 10mΩ Q2 IRLR2908 VIN 12V D2* R4 SMAJ58CA 10Ω Q3 2N3904 R5 1M 6 D1 1N4148 Q1 IRLR2908 R7 10k R3 10Ω 4 GATE 5 SNS VCC VOUT 12V, 3A CLAMPED AT 16V 3 OUT FB 2 R1 59k R2 4.99k D3** IN4148 LT4356DE 7 11 12 SHDN FLT AOUT IN+ * DIODES INC. ** OPTIONAL COMPONENT FOR REDUCED STANDBY CURRENT GND 10 EN TMR 1 CTMR 0.1µF 8 9 4356 TA08 4356fb For more information www.linear.
PAGE 22
LT4356-1/LT4356-2 Package Description Please refer to http://www.linear.com/product/LT4356-1#packaging for the most recent package drawings. DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev D) 0.70 ±0.05 3.60 ±0.05 2.20 ±0.05 3.30 ±0.05 1.70 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.50 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ±0.10 (2 SIDES) 7 R = 0.115 TYP 0.40 ± 0.10 12 R = 0.
PAGE 23
LT4356-1/LT4356-2 Package Description Please refer to http://www.linear.com/product/LT4356-1#packaging for the most recent package drawings. MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev F) 0.889 ±0.127 (.035 ±.005) 5.10 (.201) MIN 3.20 – 3.45 (.126 – .136) 3.00 ±0.102 (.118 ±.004) (NOTE 3) 0.50 0.305 ±0.038 (.0197) (.0120 ±.0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 10 9 8 7 6 3.00 ±0.102 (.118 ±.004) (NOTE 4) 4.90 ±0.152 (.193 ±.006) DETAIL “A” 0.497 ±0.
PAGE 24
LT4356-1/LT4356-2 Package Description Please refer to http://www.linear.com/product/LT4356-1#packaging for the most recent package drawings. S Package 16-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610 Rev G) .386 – .394 (9.804 – 10.008) NOTE 3 .045 ±.005 .050 BSC 16 N 14 13 12 11 10 9 N .245 MIN .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) 1 .030 ±.005 TYP 15 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.
PAGE 25
LT4356-1/LT4356-2 Revision History (Revision history begins at Rev A) REV DATE DESCRIPTION PAGE NUMBER A 05/10 Revised Features and Description Added parameters to VOL and updated Max value for VSHDN(FLT) in the Electrical Characteristics section Revised Pin Functions section B 09/17 1 4, 5 8 Replaced Figure 6 and made text edits in the Operation and Applications Information sections 10-17 Updated drawings in the Typical Applications section 19, 21 Updated TMR pin function with minimum recom
PAGE 26
LT4356-1/LT4356-2 Typical Application Overvoltage Regulator with Linear Regulator Up to 100mA Q2 2N2905A RSNS 10mΩ VIN 12V Q1 IRLR2908 D2* SMAJ58A R6 100k 11 7 R1 59k 3 OUT VCC FB 2 R2 4.99k LT4356DE AOUT 12 IN+ SHDN FLT GND *DIODES INC. 2.5V, 100mA VOUT 12V, 3A CLAMPED AT 16V R3 10Ω 4 GATE 5 SNS 6 C5 10µF EN TMR 10 1 8 R4 249k C3 47nF R5 249k 9 4356 TA09 CTMR 0.