LT®3483 micropower inverting DC/DC converter with integrated Schottky
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LT3483 Inverting Micropower DC/DC Converter with Schottky DESCRIPTION
LT®3483 micropower inverting DC/DC converter with integrated Schottky resistor feedback. small package size, high level integration tiny surface mount components yield solution size small 40mm2. device features quiescent current only load, which further reduces 0.1A shutdown. current limited, fixed off-time control scheme conserves operating current, resulting high efficiency over broad range load current. precisely trimmed feedback current enables resistor feedback virtually eliminates feedback loading output. switch enables voltage outputs -38V generated without costly transformers. LT3483's 300ns off-time permits tiny profile inductors capacitors minimize footprint cost space-conscious portable applications. LT3483 available profile (1mm) SOT-23 (ThinSOTTM) 8-lead (2mm 0.75mm) packages.
Lare registered trademarks Linear Technology Corporation. ThinSOT trademark Linear Technology Corporation. other trademarks property their respective owners. Patent Pending
Internal Schottky Diode Resistor Feedback (Other Resistor Inside) Internal 40V, 200mA Power Switch Generates Regulated Negative Outputs -38V Quiescent Current: Active Mode Shutdown Mode VCESAT Switch: 200mV 150mA Wide Input Range: 2.5V Uses Small Surface Mount Components Output Short-Circuit Protected Available 6-Lead SOT-23 Profile 8-Lead (2mm 0.75mm) Packages
APPLICATIONS
Bias Handheld Computers Battery Backup Digital Cameras OLED Bias
TYPICAL APPLICATION
3.6V DC/DC Converter
3.6V 0.22F
Efficiency Power Loss
3.6V EFFICIENCY 1000
4.7F LT3483 SHDN 806k EFFICIENCY VOUT 25mA 2.2F
POWER LOSS (mW)
POWER LOSS
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LOAD CURRENT (mA)
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LT3483 ABSOLUTE MAXIMUM RATINGS
(Note
Voltage Voltage Voltage -40V Voltage 2.5V SHDN Voltage
Operating Ambient Temperature Range (Note LT3483E 40°C 85°C LT3483I 40°C 125°C Junction Temperature 125°C Storage Temperature Range. -65°C 150°C Lead Temperature (Soldering, sec) (TSOT-23 Package Only) 300°C
CONFIGURATION
VIEW VIEW SHDN PACKAGE 6-LEAD PLASTIC TSOT-23 TJMAX 125°C, 256°C/W FREE 120°C/W BOARD OVER GROUND PLANE SHDN
PACKAGE 8-LEAD (2mm 2mm) PLASTIC TJMAX 125°C, 121°C/W EXPOSED (PIN
ORDER INFORMATION
LEAD FREE FINISH LT3483EDC#PBF LT3483ES6#PBF LT3483IDC#PBF LT3483IS6#PBF LEAD BASED FINISH LT3483EDC LT3483ES6 TAPE REEL LT3483EDC#TRPBF LT3483ES6#TRPBF LT3483IDC#TRPBF LT3483IS6#TRPBF TAPE REEL LT3483EDC#TR LT3483ES6#TR PART MARKING LCYT LTBKX LCYT LTBKX PART MARKING LCYT LTBKX PACKAGE DESCRIPTION 8-Lead (2mm 2mm) Plastic 6-Lead Plastic TSOT-23 8-Lead (2mm 2mm) Plastic 6-Lead Plastic TSOT-23 PACKAGE DESCRIPTION 8-Lead (2mm 2mm) Plastic 6-Lead Plastic TSOT-23 TEMPERATURE RANGE -40°C 85°C -40°C 85°C -40°C 125°C -40°C 125°C TEMPERATURE RANGE -40°C 85°C -40°C 85°C
Consult Marketing parts specified with wider operating temperature ranges. Consult Marketing information non-standard lead based finish parts. more information lead free part marking, http://www.linear.com/leadfree/ more information tape reel specifications,
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LT3483 ELECTRICAL CHARACTERISTICS
PARAMETER Operating Range Undervoltage Lockout Comparator Trip Voltage (VFB) Output Current (Note Comparator Hysteresis Quiescent Current Shutdown Quiescent Current (Not Switching) Line Regulation Switch Off-Time Switch Current Limit Switch VCESAT Switch Leakage Current Rectifier Leakage Current Rectifier Forward Drop SHDN Input Voltage SHDN Input High Voltage SHDN Current Note Stresses beyond those listed under Absolute Maximum Ratings cause permanent damage device. Exposure Absolute Maximum Rating condition extended periods affect device reliability lifetime. 150mA 150mA 0.64 Falling Rising VSHDN -0.05V 2.5V
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. 3.6V, VSHDN 3.6V unless otherwise specified.
CONDITIONS -10.2 0.07 -9.7 UNITS
Note LT3483E guaranteed meet specifications from 85°C. Specifications over -40°C 85°C operating temperature range assured design, characterization correlation with statistical process controls. LT3483I guaranteed meet specifications over -40°C 125°C operating temperature range. Note Current flows pin.
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LT3483 TYPICAL PERFORMANCE CHARACTERISTICS
Current
10.2
Voltage
SWITCH TIME (ns) TEMPERATURE (°C)
Switch Time
10.1 CURRENT VOLTAGE (mV)
10.0
TEMPERATURE (°C)
TEMPERATURE (°C)
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Switch Current Limit
QUIESCENT CURRENT
Quiescent Current
SHDN BIAS CURRENT
SHDN Bias Current
25°C
SWITCH CURRENT LIMIT (mA)
TEMPERATURE (°C)
TEMPERATURE (°C)
SHDN VOLTAGE
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LT3483 FUNCTIONS
(DFN/TSOT-23)
(Pin 1/Pin Feedback. Place resistor negative output here. resistor value VOUT/10A. (Pins 3/Pin Ground. package, both together ground. (Pin 4/Pin Switch. Connect external inductor positive terminal transfer capacitor. (Pin 5/Pin Input Supply. Must locally bypassed with greater. (Pin 6/NA): Connection.
(Pin 7/Pin Anode Terminal Integrated Schottky Diode. Connect negative terminal transfer capacitor external inductor (flyback configuration) cathode external Schottky diode (inverting charge pump configuration). SHDN (Pin 8/Pin Shutdown. Connect turn device off. Connect supply turn device Exposed (Pin 9/NA): GND. exposed should soldered ground achieve rated thermal performance.
BLOCK DIAGRAM
CFLY
VOUT COUT
1.250V REFERENCE 125k VOUT 300ns DELAY
25mV
20mV
OPTIONAL CHARGE PUMP CONFIGURATION. REPLACED WITH: VOUT NUMBERS CORRESPOND 6-PIN TSOT-23 PACKAGE
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LT3483 OPERATION
LT3483 uses constant off-time control scheme provide high efficiency over wide range output currents. Operation best understood referring Block Diagram. When voltage approximately comparator disables most internal circuitry. Output current then provided external capacitor COUT, which slowly discharges until voltage goes above hysteresis point Typical hysteresis 10mV. then enables internal circuitry, turns power switch currents external inductors begin ramp Once switch current reaches 200mA, comparator resets latch, which turns after about 80ns. Inductor current flows through internal Schottky GND, charging flying capacitor. Once 300ns off-time elapsed, internal diode current drops below 250mA detected comparator A2), turns again ramps 200mA. This switching action continues until output capacitor charge replenished (until decreases 0V), then turns internal circuitry cycle repeats. inverting charge pump topology replaces with series combination
APPLICATIONS INFORMATION
CHOOSING REGULATOR TOPOLOGY Inverting Charge Pump inverting charge pump regulator combines inductor-based step-up with inverting charge pump. This configuration usually provides best size, efficiency output ripple applicable where magnitude VOUT greater than VIN. Negative outputs -38V produced with LT3483 this configuration. cases where magnitude VOUT less than equal VIN, 2-inductor transformer configuration such inverting flyback. inverting charge pump configuration, resistor added series with Schottky diode between negative output LT3483. purpose this resistor smooth/reduce current spike flying capacitor when switch turns resistor works well application, impact converter efficiency less than resistor values recommended applications circuits also limit switch current during short-circuit condition output. Inverting Flyback inverting flyback regulator, shown application circuit, uses coupled inductor excellent choice where magnitude output less than equal supply voltage. inverting flyback also performs well step-up/invert application, occupies more board space compared with inverting charge pump. Also, maximum |VOUT| using flyback less than obtained with charge pump-it reduced from magnitudes ringing switch node. Under short-circuit condition output, proprietary technique limits switch current prevents damage LT3483 even with supply voltage high 16V. option, 0.47F capacitor added between terminals LT3483 suppress ringing Inductor Selection Several recommended inductors that work well with LT3483 listed Table although there many other manufacturers devices that used. Consult each manufacturer more detailed information their entire selection related parts. Many different sizes shapes available. inverting charge pump regulators with input output voltages below 4.7H 6.8H inductor usually best choice. flyback regulators inverting charge pump regulators where input output voltage greater than inductor usually best choice. larger value inductor used slightly increase available output current, limit
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LT3483 APPLICATIONS INFORMATION
around twice value recommended, large inductance will increase output voltage ripple without providing much additional output current.
Table Recommended Inductors
HEIGHT (mA) (mm) MANUFACTURER 0.84 0.72 1.15 0.46 0.95 Murata www.murata.com Cooper Electronics Tech www.cooperet.com Elektronik www.we-online.com
4.7F following formula useful estimate output capacitor value needed: COUT -VOUT VOUT
PART LQH2MCN4R7M02L LQH2MCN6R8M02L LQH2MCN100M02L SDQ12 Coupled Inductor 744876 Coupled Inductor
where 0.25A VOUT 30mV. flying capacitor inverting charge pump configuration ranges from 0.1F 0.47F Multiply value predicted above equation COUT 1/10 determine value needed flying capacitor.
Table Recommended Ceramic Capacitor Manufacturers
MANUFACTURER Kemet Murata Taiyo Yuden www.avxcorp.com www.kemet.com www.murata.com www.tyuden.com
Capacitor Selection small size ceramic capacitors make them ideal LT3483 applications. types recommended because they retain their capacitance over wider voltage temperature ranges than other dielectric types. Always verify proper voltage rating. Table shows list several ceramic capacitor manufacturers. Consult manufacturers more detailed information their entire selection ceramic capacitors. 4.7F ceramic bypass capacitor recommended where distance power supply battery could more than couple inches. Otherwise, adequate. capacitor parallel with feedback resistor recommended reduce output voltage ripple. capacitor inverting charge pump, 22pF value inverting flyback other dual inductor configurations. Output voltage ripple reduced 20mV some cases using this capacitor combination with appropriately selected output capacitor. output capacitor selected based desired output voltage ripple. output voltage ripple inverting flyback configuration, 4.7F capacitor. inverting charge pump utilizes values ranging from 0.22F
Setting Output Voltage output voltage programmed using feedback resistor according following formula: VOUT
Inrush Current When increased from ground operating voltage, inrush current will flow through input inductor integrated Schottky diode charge flying capacitor. Conditions that increase inrush current include larger, more abrupt voltage step VIN, larger flying capacitor, inductor with saturation current. While internal diode designed handle such events, inrush current should allowed exceed 1.5A. circuits that flying capacitors within recommended range have input voltages less than inrush current remains low, posing hazard device. cases where there large steps VIN, inrush current should measured ensure operation within limits device.
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LT3483 APPLICATIONS INFORMATION
Board Layout Considerations with switching regulators, careful attention must given board layout component placement. Proper layout high frequency switching path essential. voltage signals pins have sharp rising falling edges. Minimize length area traces connected pins. particular, desirable minimize trace length from flying capacitor, since current this capacitor switches directions within cycle. Always ground plane under switching regulator minimize interplane coupling.
Suggested Layout (DFN) Inverting Charge Pump
VOUT COUT
SHDN CFLY
3483 AI02
Suggested Layout (SOT-23) Inverting Charge Pump
CFLY COUT SHDN
VOUT
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LT3483 TYPICAL APPLICATION
3.6V DC/DC Converter Profile, Small Footprint
0.22F 4.7F LT3483 SHDN 806k
3.6V
VOUT 25mA 2.2F
MURATA GRM219R61A475KE34B TAIYO YUDEN LMK107BJ224 MURATA GRM219R61C225KA88B PHILIPS PMEG2005EB MURATA LQH2MCN100K02L
3483 TA04a
Switching Waveform
VOUT 20mV/DIV
100mA/DIV
2s/DIV
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LT3483 PACKAGE DESCRIPTION
Package 8-Lead Plastic (2mm 2mm)
(Reference 05-08-1719
0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 0.64 ±0.05 SIDES) PACKAGE OUTLINE
0.25 0.05 0.45 1.37 ±0.05 SIDES) RECOMMENDED SOLDER PITCH DIMENSIONS APPLY SOLDER MASK AREAS THAT SOLDERED 0.05 2.00 ±0.10 SIDES)
0.115
0.40 0.10 NOTCH 0.20 0.25 CHAMFER
(DC8) 0106
MARK (SEE NOTE
0.64 0.10 SIDES)
0.200 0.75 ±0.05 1.37 ±0.10 SIDES) 0.00 0.05
0.23 0.05 0.45
BOTTOM VIEW-EXPOSED
NOTE: DRAWING JEDEC PACKAGE OUTLINE DRAWING SCALE DIMENSIONS MILLIMETERS DIMENSIONS EXPOSED BOTTOM PACKAGE INCLUDE MOLD FLASH. MOLD FLASH, PRESENT, SHALL EXCEED 0.15mm SIDE EXPOSED SHALL SOLDER PLATED SHADED AREA ONLY REFERENCE LOCATION BOTTOM PACKAGE
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LT3483 PACKAGE DESCRIPTION
Package 6-Lead Plastic TSOT-23
(Reference 05-08-1636
0.62 0.95 2.90 (NOTE
1.22
3.85 2.62
2.80
1.50 1.75 (NOTE
RECOMMENDED SOLDER LAYOUT CALCULATOR
0.95
0.30 0.45 PLCS (NOTE
0.80 0.90 0.20 DATUM 1.00 0.01 0.10
0.30 0.50
NOTE: DIMENSIONS MILLIMETERS DRAWING SCALE DIMENSIONS INCLUSIVE PLATING DIMENSIONS EXCLUSIVE MOLD FLASH METAL BURR MOLD FLASH SHALL EXCEED 0.254mm JEDEC PACKAGE REFERENCE MO-193
0.09 0.20 (NOTE
1.90
TSOT-23 0302
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Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology Corporation makes representation that interconnection circuits described herein will infringe existing patent rights.
LT3483 TYPICAL APPLICATIONS
3.6V -22V DC/DC Converter
0.1F EFFICIENCY EFFICIENCY 4.7F LT3483 SHDN 2.2M VOUT -22V POWER LOSS (mW)
3.6V -22V Converter Efficiency Power Loss
1000
3.6V
POWER LOSS
TAIYO YUDEN LMK316BJ475MD TAIYO YUDEN TMK107BJ104 (X5R) TAIYO YUDEN TMK316BJ105MD PHILIPS PMEG3002AEB MURATA LQH2MCN100K02L
3483 TA02a
LOAD CURRENT (mA)
3483 TA02b
DC/DC Converter
Efficiency
EFFICIENCY VOUT 22pF 511k
4.7F
LT3483 SHDN
TAIYO YUDEN EMK316BJ475ML TAIYO YUDEN JMK316BJ106ML L1A, L1B: WURTH 744876100
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LOAD CURRENT (mA)
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RELATED PARTS
PART NUMBER LT1617/LT1617-1 LT1931/LT1931A LT1945 LT3463 DESCRIPTION 350mA/100mA (ISW) High Efficiency Micropower Inverting DC/DC Converter (ISW), 1.2MHz/2.2MHz, High Efficiency Micropower Inverting DC/DC Converter Dual Output, Boost/Inverter, 350mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter Dual Output, Boost/Inverter, 250mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter with Integrated Schottky Diodes 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky Disconnect Boost (350mA) Inverting (400mA) DC/DC Converter Bias with Integrated Schottkys COMMENTS VIN: 1.2V 15V, VOUT(MAX) -34V, 20A, ThinSOT Package VIN: 2.6V 16V, VOUT(MAX) -34V, 5.8mA, ThinSOT Package VIN: 1.2V 15V, VOUT(MAX) ±34V, 40A, MS10 Package VIN: 2.3V 15V, VOUT(MAX) ±40V, 40A, Package VIN: 2.3V 10V, VOUT(MAX) 34V, 25A, ThinSOT Package VIN: 2.3V 15V, VOUT(MAX) ±40V, 2.8mA, Package
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LT3464 LT3472
Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
0508 PRINTED
1630 McCarthy Blvd., Milpitas, 95035-7417
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004
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