LT3420/LT3420-1 Photoflash Capacitor Chargers with Automatic Refresh D
|
|
|
Top Searches for this datasheet
LT3420/LT3420-1 Photoflash Capacitor Chargers with Automatic Refresh DESCRIPTIO
LT®3420/LT3420-1 charge high voltage photoflash capacitors quickly efficiently. Designed both digital film cameras, these devices flyback topology achieve efficiencies four times better than competing flash modules. unique adaptive off-time control algorithm* maintains current-limited continuous mode transformer operation throughout entire charge cycle, eliminating high inrush current often found modules. LT3420/LT3420-1 output voltage sensing scheme* monitors flyback voltage indirectly regulate output voltage, eliminating output resistor divider discrete zener diode. This feature allows capacitor held fully charged state without excessive power consumption. Automatic refresh (which defeated) allows capacitor remain charged while consuming average input current about 2mA, user-defined refresh rate. logic high CHARGE initiates charging, while DONE signals that capacitor fully charged. LT3420/LT3420-1 available 10-Lead MSOP (3mm 3mm) packages.
registered trademarks Linear Technology Corporation. other trademarks property their respective owners. *Protected U.S. Patents including 6518733.
Charges 220µF 320V Seconds from (LT3420) Charges 100µF 320V Seconds from (LT3420-1) Charges Size Photoflash Capacitor Supports Operation from Cells Supply from 1.8V Controlled Peak Switch Current: 1.4A (LT3420) 1.0A (LT3420-1) Controlled Input Current: 840mA (LT3420) 450mA (LT3420-1) Uses Standard Transformers Efficient Flyback Operation (>75% Typical) Adjustable Output Automatic Refresh Charge Complete Indicator High Voltage Zener Diode Required Output Voltage Divider Required Small 10-Lead MSOP Package Small 10-Lead (3mm 3mm) Package
APPLICATIO
Digital Camera Flash Unit Film Camera Flash Unit High Voltage Power Supplies
TYPICAL APPLICATIO
VBAT 1.8V INPUT CURRENT 350mA 1:12 4.7µF 51.1k VBAT LT3420 CHARGE DONE 0.1µF 4.7µF, X7R, RUBYCON 220µF PHOTOFLASH CAPACITOR SRW10EPC-U01H003 FLYBACK TRANSFORMER VISHAY GSD2004S SOT-23 DUAL DIODE. DIODES CONNECTED SERIES RREF
320V
VBAT 1.8V INPUT CURRENT 450mA
VBAT
2.5V
4.7µF
220µF 330V PHOTOFLASH CAPACITOR
2.5V
CHARGE DONE
CHARGE DONE
DANGER HIGH VOLTAGE OPERATION HIGH VOLTAGE TRAINED PERSONNEL ONLY
3420
4.7µF, X7R, 6.3V RUBYCON 100µF PHOTOFLASH CAPACITOR KIJIMA MUSEN SBL-5.6S-2 VISHAY GSD2004S SOT-23 DUAL DIODE. DIODES CONNECTED SERIES
Figure High Charge Rate LT3420 Photoflash Circuit
Figure Small Size LT3420-1 Photoflash Circuit
3420fb
1:10 (3mm TALL) 4.7µF
320V
60.4k LT3420-1 CHARGE DONE 0.1µF RREF
4.7µF
100µF 330V PHOTOFLASH CAPACITOR
3420
LT3420/LT3420-1
ABSOLUTE
(Note
RATI
DONE Voltage Current into DONE ±1mA Maximum Junction Temperature 125°C Operating Ambient Temperature Range (Note 40°C 85°C Storage Temperature Range 40°C 125°C Lead Temperature (Soldering, sec) (For Package only) 300°C
Voltage VBAT Voltage Voltage (Note LT3420 LT3420-1 Current ±200mA Current ±3mA RREF Voltage 2.5V CHARGE Voltage Voltage 1.5V
PACKAGE/ORDER INFORMATION
VIEW RREF VBAT CHARGE DONE
ORDER PART NUMBER
VIEW
LT3420EDD LT3420EDD-1 PART MARKING LBJW LBJX
PACKAGE 10-LEAD (3mm 3mm) PLASTIC
TJMAX 125°C, 43°C/W, 3°C/W EXPOSED (PIN MUST SOLDERED
Consult Marketing parts specified with wider operating temperature ranges.
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. VBAT 3.3V, VCHARGE unless otherwise noted. (Note
PARAMETER Minimum Operating Voltage, Maximum Operating Voltage, UVLO Hysteresis Minimum VBAT Voltage Maximum VBAT Voltage VBAT UVLO Hysteresis RREF Threshold Voltage
ELECTRICAL CHARACTERISTICS
CONDITIONS
RREF Bias Current Quiescent Current Quiescent Current Shutdown
VRREF Switching VRFB VBAT 0.2V (Note VRREF 1.1V, Switching VCHARGE 3.3V
ORDER PART NUMBER
CHARGE DONE
RREF VBAT
LT3420EMS LT3420EMS-1 PART MARKING LTYH LTAJG
PACKAGE 10-LEAD PLASTIC MSOP TJMAX 125°C, 100°C/W, 45°C/W (4-LAYER BOARD)
UNITS
0.98 0.975
1.00 0.01
1.02 1.025
3420fb
LT3420/LT3420-1
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. VBAT 3.3V, VCHARGE unless otherwise noted. (Note
PARAMETER Primary Side Current Limit Secondary Side Current Limit Leakage Blanking Pulse Width Refresh Timer Charge/Discharge Current Refresh Timer Upper Threshold Refresh Timer Lower Threshold Switch VCESAT Switch Leakage Current CHARGE Input Voltage High CHARGE Input Voltage CHARGE Bias Current DONE Output Signal High DONE Output Signal VCHARGE VCHARGE 100k from DONE 33µA into DONE 0.01 LT3420, (Note LT3420-1, 0.5A (Note (LT3420), (LT3420-1) CONDITIONS LT3420 (Note LT3420-1 (Note LT3420 (Note LT3420-1 (Note LT3420 LT3420-1 0.75V 0.45 1.20 0.75 0.01 0.55 1.60 1.05 UNITS
ELECTRICAL CHARACTERISTICS
Note Absolute Maximum Ratings those values beyond which life device impaired. Note Rated breakdown with LT3420 power delivery mode power switch off. Note LT3420/LT3420-1 guaranteed meet performance specifications from 70°C. Specifications over -40°C 85°C
operating temperature range assured design, characterization correlation with statistical process controls. Note Bias current flows pin. Note Current limit VCESAT guaranteed design and/or correlation static test package.
TYPICAL PERFOR CHARACTERISTICS
Graphs apply both LT3420 LT3420-1 unless otherwise noted. Output Voltage Refresh Mode, LT3420
VOUT
VOUT
TIME
FIGURE CIRCUIT 3.3V VBAT 3.3V TEMPERATURE (°C)
3420
Output Voltage Refresh Mode, LT3420
FIGURE CIRCUIT VBAT 25°C
3420
Charge Time, LT3420
FIGURE CIRCUIT UNLESS OTHERWISE NOTED. VOUT CHARGED FROM 320V 25°C
COUT 220µF COUT 100µF
VBAT
3420
3420fb
LT3420/LT3420-1 TYPICAL PERFOR CHARACTERISTICS
Graphs apply both LT3420 LT3420-1 unless otherwise noted. Output Voltage Refresh Mode, LT3420-1
VOUT
VOUT
TIME
FIGURE CIRCUIT 3.3V VBAT 3.3V TEMPERATURE (°C)
3420
Charge Input Current
25°C
CURRENT (µA)
CURRENT (mA)
CURRENT
CHARGE VOLTAGE
Efficiency Figure Circuit, LT3420
25°C
EFFICIENCY
CURRENT (mA)
3.3V CURRENT
VBAT VOUT
3420
3420
Output Voltage Refresh Mode, LT3420-1
FIGURE CIRCUIT VBAT 25°C
3420
Charge Time, LT3420-1
FIGURE CIRCUIT VOUT CHARGED FROM 320V 25°C
COUT 100µF COUT 40µF
VBAT
3420
Primary Current Limit, LT3420
Secondary Current Limit, LT3420
TEMPERATURE (°C)
TEMPERATURE (°C)
3420
3420
Primary Current Limit, LT3420-1
Secondary Current Limit, LT3420-1
TEMPERATURE (°C)
TEMPERATURE (°C)
3420
3420
3420fb
LT3420/LT3420-1 TYPICAL PERFOR CHARACTERISTICS
Graphs apply both LT3420 LT3420-1 unless otherwise noted. Efficiency Figure Circuit, LT3420-1
25°C
AVERAGE INPUT CURRENT (mA)
3.3V
AVERAGE INPUT CURRENT (mA)
EFFICIENCY
VBAT VOUT
3420
Quiescent Current Refresh Mode
25°C
QUIESCENT CURRENT (µA)
VBAT VOLTAGE
VOLTAGE
3420
Input Current, LT3420
1000 FIGURE CIRCUIT VBAT 3.3V 25°C
Input Current, LT3420-1
FIGURE CIRCUIT VBAT 3.3V 25°C
VOUT
3420
VOUT
3420
Minimum Operating Voltage
ENABLE VOLTAGE HYSTERETIC
VBAT Minimum Operating Voltage
ENABLE VOLTAGE HYSTERETIC
TEMPERATURE (°C)
3420
TEMPERATURE (°C)
3420
3420fb
LT3420/LT3420-1
CTIO
RREF (Pin Reference Resistor Pin. Place resistor (R2) from RREF GND. recommended. VBAT (Pin Battery Voltage Input. This should connected power supply battery, which supplies power transformer Must locally bypassed. (Pin Feedback Resistor Pin. Place resistor (R1) from pin. according following formula:
[(1.4
N(VOUT
[(RSEC N(VOUT (LT3420-1)
VOUT Desired Output Voltage Transformer Turns Ratio RSEC: Transformer Secondary Resistance Diode Forward Voltage Drop Resistor from RREF GND. Typical Choice (Pin Input Supply Pin. Must locally bypassed with 4.7µF larger ceramic capacitor.
(Pin Ground. directly local ground plane. (Pin Switch Pin. This collector internal power switch. Minimize metal trace area connected this minimize EMI. (Pin Transformer Secondary Pin. transformer secondary this pin. Take care correct phasing transformer (Refer Figures DONE (Pin Done Output Pin. Open collector output. DONE pulled whenever chip delivering power output goes high when power delivery stops. CHARGE (Pin Charge Pin. Drive CHARGE high (1.5V more) commence charging output capacitor. Drive 0.2V less part shutdown mode. (Pin 10): Refresh Timer Capacitor Pin. Place capacitor from refresh timer sample rate according following formula: tREFRESH tREFRESH: Desired Refresh Period Seconds. EXPOSED (Pin Package only): GND. Must soldered local ground plane PCB.
(LT3420)
3420fb
LT3420/LT3420-1
BLOCK DIAGRA
VBAT PRIMARY DONE VBAT RREF PHOTOFLASH CAPACITOR DRIVER ONESHOT 1:12 SECONDARY VOUT
REFRESH TIMER
CHARGE
ONESHOT CHIP ENABLE
POWER DELIVERY BLOCK
Figure Block Diagram, LT3420
VBAT PRIMARY DONE VBAT RREF PHOTOFLASH CAPACITOR DRIVER ONESHOT 1:10 SECONDARY VOUT
REFRESH TIMER
CHARGE
ONESHOT CHIP ENABLE
POWER DELIVERY BLOCK
Figure Block Diagram, LT3420-1
3420fb
REFERENCE
MASTER LATCH
BLOCK ENABLE
REFERENCE
MASTER LATCH
BLOCK ENABLE
ENABLE
ENABLE
20mV
0.014
10mV 0.25
LT3420
3420
20mV
0.02
10mV 0.66
LT3420-1
3420
LT3420/LT3420-1
OPERATIO
Overview
following text focuses operation LT3420. operation LT3420-1 nearly identical with differences discussed this section. LT3420 uses adaptive on-time/off-time control scheme provide excellent efficiency precise control switching currents. Please refer Figure following overview part's operation. given instant, master latch determines which mode LT3420 "charging" "refresh". charging mode, circuitry enclosed smaller dashed enabled, providing power charge photoflash capacitor output voltage monitored flyback pulse primary transformer. When target output voltage reached, charging mode terminated part enters refresh mode. refresh mode, power delivery block disabled, reducing quiescent current, while refresh timer enabled. refresh timer simply generates user programmable delay, after which part reenters charging mode. Once charging mode, LT3420 will again provide power output until target voltage reached. Figure oscillograph photo showing both initial charging photoflash capacitor subsequent refresh action. upper waveform output voltage. middle waveform voltage pin. lower waveform shows input current. mode part indicated below photo. user defeat refresh timer force part into charging mode toggling CHARGE
VOUT 100V/DIV
1V/DIV
1A/DIV
MODE SHUTDOWN
Figure Demonstrating Operating Modes LT3420: Shutdown, Charging Refresh Photoflash Capacitor
(highlowhigh). high transition CHARGE fires one-shot that sets master latch, putting part charging mode. Bringing CHARGE puts part shutdown. refresh timer programmed wait indefinitely simply grounding pin. this configuration, LT3420 will only reenter charging mode toggling CHARGE pin. Power Delivery Block power delivery block consists circuitry enclosed smaller dashed Figure This circuit block contains elements needed charging output voltage detection. better understand circuit operation, follow subsequent description cycle operation refer Figure Assume that initially there current primary secondary transformer, output comparator low, while that high (note small offset voltages inputs A2). latch thus power switch, turned Current increases linearly primary transformer rate determined VBAT voltage primary inductance transformer. current builds voltage across resistor increases. When this voltage exceeds 20mV offset voltage output goes high, resetting latch turning current needed reset latch approximately 1.4A (~20mV/14m). When turns off, secondary side current quickly jumps from zero current primary side current divided (the turns ratio transformer T1). this example, peak secondary current 116mA (1.4A/12). Diode conducts, providing power output. Since positive voltage exists across secondary winding transformer, secondary current decreases linearly rate determined secondary inductance output voltage (neglecting diode voltage drop). When secondary side current drops below 40mA (10mV/0.25), output goes high, setting latch turning initial primary current simply minimum secondary current times this case 0.48A (40mA will remain until primary current again reaches 1.4A. This cycle operation repeats itself, automatically adjusting times
3420fb
CHARGING 1s/DIV
REFRESH
3420
LT3420/LT3420-1
OPERATIO
1A/DIV
ISEC 200mA/DIV
20V/DIV 2µs/DIV
3420 F06a
Figure Switching Waveforms with VOUT 100V, VBAT 3.3V
that peak current 1.4A minimum secondary current 40mA (typical values). previously described charging cycle must halted when output voltage reaches desired value. LT3420 monitors output voltage flyback pulse pin. When turns off, secondary side conducts current turning diode Since diode conducting nearly ground, voltage across secondary nearly equal VOUT. voltage across primary therefore close VOUT/N. current proportional VOUT/N flows through into pin. current flows RREF through resistor creating ground referred voltage. When this voltage exceeds internal reference voltage, output comparator goes high which resets master latch. output master latch goes low, disabling entire power delivery block enabling refresh timer. Leakage Spike Blanking Another function LT3420 leakage spike blanking when power switch, turns off. Right after turns off, one-shot turns 200ns (typ). With comparator disabled. This function prevent from false tripping leakage inductance spike pin. practice, transistor filters leakage spike. Refresh Timer When refresh timer enabled, 2.5µA current source switched charging external timing capacitor,
1A/DIV ISEC 200mA/DIV 20V/DIV 2µs/DIV
3420 F06b
Figure Switching Waveforms with VOUT 300V, VBAT 3.3V
from initial voltage towards When voltage reaches polarity current source changes 2.5µA discharges When voltage reaches 0.5V, refresh timer sends pulse master latch, which puts LT3420 into charging mode. Interface/Control CHARGE serves functions. first enable shutdown part depending level (high enable, shutdown). second force part into charging mode (lowhigh transition). LT3420 also DONE pin, which signals whether part done charging photoflash capacitor. DONE open collector switch (Q5) external pull-up resistor needed. Whenever part charging mode, DONE will low. DONE will high when charging mode complete. Both CHARGE DONE pins easily interfaced microprocessor digital film camera. LT3420-1 Differences LT3420-1 different primary secondary current limit levels. primary current limit level LT3420-1 (typ) secondary current limit 15mA (typ). LT3420-1 leakage spike blanking which causes problems since transistor, provides adequate filtering. Finally, breakdown voltage LT3420-1 higher 50V.
3420fb
LT3420/LT3420-1
APPLICATIO ATIO
COMPONENT SELECTION Choosing Right Transformer
flyback transformer plays role LT3420/ LT3420-1 application. poorly designed transformer result inefficient operation. Linear Technology Corporation worked with number transformer manufacturers develop specific transformers with LT3420/LT3420-1. These predesigned transformers sufficient large majority applications that encountered. some cases, reader choose design transformer simply curious about issues involved designing transformer. following brief discussion issues relating transformer design. Transformer Turns Ratio turns ratio transformer, should high enough that absolute maximum voltage rating power switch exceeded. When power switch turns off, voltage collector switch Pin) will "fly" output voltage divided plus battery voltage (neglecting voltage drop across rectifying diodes). This voltage should exceed (LT3420) (LT3420-1) breakdown rating power switch. Choose minimum following formula.
VOUT (LT3420) VBAT VOUT NMIN (LT3420 VBAT NMIN
LT3420 design, battery voltage 330V output results NMIN turns ratio greater should used.
Transformer Primary Inductance flyback transformer needs store substantial amounts energy core during each switching cycle. transformer, therefore, will generally require gap. core makes energy storage ability, inductance, much more stable with temperature variations core material. Most core manufacturers will supply standard sizes gaps with given type core, resulting different values. inductance particular core square turns winding. certain inductance, simply divide desired inductance value take square root result find number turns needed primary transformer. LT3420/LT3420-1 detect output voltage flyback pulse pin. Since this only occur while power switch off, important criteria that value primary inductance transformer larger than certain minimum value. switch time should 500ns larger LT3420 350ns larger LT3420-1. minimum inductance calculated with following formula:
LPRI LPRI VOUT (1.4 0.04N) (LT3420) VOUT (LT3420 (1.0 0.015N)
VOUT: Target Output Voltage Transformer Turns Ratio Transformer Leakage Inductance leakage inductance transformer must carefully minimized both proper efficient operation part. voltage rating LT3420 while LT3420-1 50V. These ratings blocking voltages only additional precautions
3420fb
LT3420/LT3420-1
APPLICATIO ATIO
must taken into account dynamic blocking voltage capabilities LT3420/LT3420-1. dynamic blocking voltage capability both parts 38V. Table summarizes various breakdown voltages both parts.
Table Voltage Ratings
PART LT3420 LT3420-1 RATING DYNAMIC RATING
Figure shows what examine transformer design determine specifications met. first leakage inductance spike labeled must exceed dynamic rating pin. does exceed rating, then transformer leakage inductance must lowered. flyback waveform after initial spike labeled must exceed rating pin. does exceed rating, then turns ratio transformer must lowered. measuring voltage pin, care must taken minimizing ground loop voltage probe. Careless probing will result inaccurate readings.
IPRI
3420
Figure Transformer Design Check (Not Scale)
3420fb
Note also magnitude initial current spike primary transformer labeled when power switch turns leakage inductance lowered very level, internal capacitances transformer will high. This will result initial spike current primary becoming excessively high. level should kept less typical design both LT3420 LT3420-1. Please note that inserting loop wire primary measure primary current, leakage inductance primary will made artificially high. This result erroneous voltage measurements pin. measurements shown Figure should made with both VOUT VBAT maximum levels given application. This results highest voltage current stress pin. Transformer Secondary Capacitance total capacitance secondary should minimized both efficient proper operation LT3420/ LT3420-1. Since secondary transformer undergoes large voltage swings (approaching 600VP-P), capacitance secondary severely affect
MUST LESS THAN BOTH LT3420 LT3420-1 MUST LESS THAN BOTH LT3420 LT3420-1 MUST LESS THAN LT3420 MUST LESS THAN LT3420-1
LT3420/LT3420-1
APPLICATIO ATIO
efficiency circuit. addition, effective capacitance primary largely dominated actual secondary capacitance. This simply result secondary capacitance being multiplied when reflected primary. Since generally higher, small capacitance 10pF secondary times larger, 1.0nF, primary. This capacitance forms resonant circuit with primary leakage inductance transformer. such, both primary leakage inductance secondary side capacitance should minimized. Table shows various predesigned transformers along with relevant parameters. Contact individual transformer manufacturer additional information customization.
Table Predesigned Transformers, LT3420
PART SRW10EPC -U01H003 6375-T108 TURNS SIZE RATIO (µH) LxWxH (mm) VENDOR 1:12 10.9x10.8x5.2 (847) 803-6100 www.components.tdk.com 1:12 10.8x9.5x3.6 Sumida (847) 956-0666 www.sumida.com 1:12 17.5 10.3x6.4x5.2 Kijima Musen 852-2489-8266 kijimahk@netvigator.com
SBL-6.4
Table Predesigned Transformers, LT3420-1
PART SBL-5.6S-2 TURNS RATIO (µH) 1:10 SIZE LxWxH (mm) VENDOR 5.6x8.5x3.0 Kijima Musen 852-2489-8266 kijimahk@netvigator.com 5.8x5.8x3.0 (847) 803-6100 www.components.tdk.com
LDT565630T 1:10.2 14.5 -002
DIODE SELECTION rectifying diode(s) should capacitance type with sufficient reverse voltage forward current ratings. peak reverse voltage that diode(s) will approximately: VPK-R VOUT VBAT 1.65 peak current diode simply: 1.4A (LT3420) IPK-SEC (LT3420 IPK-SEC circuit Figure with VBAT 3.3V, VPK-R 590V IPK-SEC 116mA. Table shows various diodes that work with LT3420/LT3420-1. These chosen capacitance high reverse blocking voltage. appropriate number diodes achieve necessary reverse breakdown voltage.
Table
REVERSE CAPACITANCE VOLTAGE (pF) VENDOR 2x300 Vishay (402) 563-6866 www.vishay.com BAS21 Philips Semiconductor (Single diode) (800) 234-7381 www.philips.com MMBD3004S 2x300 Diodes Inc. (805) 446-4800 www.diodes.com PART GSD2004S (Dual diode)
3420fb
LT3420/LT3420-1
APPLICATIO ATIO
CAPACITOR SELECTION
VBAT decoupling capacitors should multilayer ceramic type with dielectric. This insures adequate decoupling across wide ambient temperature ranges. good quality ceramic capacitor also recommended timing capacitor pin. Avoid dielectrics. Selectively Disabling LT3420/LT3420-1 LT3420/LT3420-1 disabled time, even during charge phase. This useful when digital camera enters sensitive data acquisition phase. Figure illustrates this feature. Midway through charge cycle, CHARGE brought low, which disables part. After sensitive data operation complete, CHARGE brought high charging operation continues. Measuring Efficiency Measuring efficiency circuit designed charge large capacitive loads difficult issue, particularly with photoflash capacitors. ideal measure efficiency capacitor charging circuit would find energy delivered output capacitor (0.5 divide total input energy. This method does work well here because photoflash capacitors from ideal. Among other things, they have relatively high leakage currents, large amounts dielectric absorption,
VOUT 50V/DIV
VCHARGE
CHARGE CHARGE
Figure Halting Charge Cycle Time
significant voltage coefficients. much more accurate, easier, method measure efficiency function output voltage. place photoflash capacitor, smaller, high quality capacitor, reducing errors associated with non-ideal photoflash capacitor. Using adjustable load, output voltage anywhere between ground maximum output voltage. efficiency measured output power (VOUT IOUT) divided input power (VIN IIN). This method also provides good means compare various charging circuits since removes variability photoflash capacitor from measurement. total efficiency circuit, charging ideal capacitor, would time average given efficiency curve, over time VOUT changes. Adjustable Input Current With many types modern batteries, maximum allowable current that drawn from battery limited. This generally accomplished active circuitry polyfuse. Different parts digital camera require high currents during certain phases operation very little other times. photoflash charging circuit should able adapt these varying currents drawing more current when rest camera drawing less, vice-versa. This helps reduce charge time photoflash capacitor, while avoiding
0.5s/DIV
3420
3420fb
LT3420/LT3420-1
APPLICATIO ATIO
risk drawing much current from battery. input current LT3420/LT3420-1 circuit adjusted driving CHARGE with (pulse width modulation) signal. microprocessor adjust duty cycle signal achieve desired level input current. Many schemes exist achieve this function. Once target output voltage reached, signal should halted avoid overcharging photoflash capacitor, since signal CHARGE overrides refresh timer. simple method achieve adjustable input current shown Figure signal frequency
1kHz SIGNAL
Figure Simple Logic Adjustable Input Current
INPUT CURRENT (mA)
LT3420-1
DUTY CYCLE
3420
Figure Input Current Duty Cycle Varied
1kHz. When logic high, circuit enabled CHARGE driven signal. When target output voltage reached, DONE goes high while CHARGE also high. output goes high, which forces CHARGE high regardless signal. part Refresh mode. Once refresh period over, DONE goes low, allowing signal drive CHARGE once again. This function easily implemented microcontroller. Figure shows input current LT3420 LT3420-1 duty cycle signal varied.
DONE CHARGE LT3420 CIRCUIT
3420
LT3420
3420fb
LT3420/LT3420-1
APPLICATIO ATIO
BOARD LAYOUT
high voltage operation LT3420/LT3420-1 demands careful attention board layout. will advertised performance with careless layout. Figures show recommended component placement. Keep area high voltage secondary small possible. Note larger than minimum spacing high voltage nodes. This
PHOTOFLASH CAPACITOR VOUT
VBAT
3420
Figure Suggested Layout (MS10 Package)
CHARGE DONE PHOTOFLASH CAPACITOR VOUT
VBAT
3420
Figure Suggested Layout Package)
3420fb
necessary meet breakdown specifications circuit board. Photoflash capacitor placed from LT3420/LT3420-1 circuit, place small (20nF50nF) ceramic capacitor with sufficient voltage rating close part. This insures adequate bypassing. Remember that LETHAL VOLTAGES PRESENT this circuit. caution when working with circuit.
CHARGE DONE
LT3420/LT3420-1
TYPICAL APPLICATIO
Professional Charger uses Multiple LT3420 Circuits Parallel Charge Large Photoflash Capacitors Quickly
VBAT 1.8V 4.7µF DANGER HIGH VOLTAGE OPERATION HIGH VOLTAGE TRAINED PERSONEL ONLY 2.5V CHARGE 1:12 320V
4.7µF, X7R, T1-T3: SRW10EPC-U01H003 FLYBACK TRANSFORMER D1-D3: VISHAY GSD2004S SOT-23 DUAL DIODE. DIODES CONNECTED SERIES 2N3904 EQUIVALENT CHARGE SIZE PHOTOFLASH CAPACITOR MANY SLAVE CHARGERS NEEDED.
52.3k
650µF* 350V PHOTOFLASH CAPACITOR
VBAT
MASTER 4.7µF LT3420 CHARGER CHARGE RREF DONE 0.1µF
VBAT 4.7µF VBAT 100k 100k
1:12
4.7µF SLAVE** LT3420 CHARGER CHARGE RREF DONE VBAT 4.7µF VBAT 1:12
2N3904
SLAVE** 4.7µF LT3420 CHARGER CHARGE RREF DONE
3420 TA01
3420fb
LT3420/LT3420-1
TYPICAL APPLICATIO
LT3420 Photoflash Charging Circuit Uses Small Transformer
DANGER HIGH VOLTAGE OPERATION HIGH VOLTAGE TRAINED PERSONEL ONLY VBAT 1.8V 4.7µF
2.5V
4.7µF, X7R, 6.3V 4.7µF, X7R, RUBYCON 220µF PHOTOFLASH CAPACITOR 3420 TA02 VISHAY GSD2004S SOT-23 DUAL DIODE. DIODES CONNECTED SERIES KIJIMA MUSEN SBL-6.4 MAXIMUM AMBIENT TEMPERATURE 60°C DICTATED TRANSFORMER
EFFICIENCY
1:12
300V
47.5k
4.7µF
VBAT
LT3420 CHARGE DONE 0.1µF RREF
220µF 330V PHOTOFLASH CAPACITOR
CHARGE DONE
Efficiency
VBAT
3.3V
VOUT
3420 TA03
3420fb
LT3420/LT3420-1
PACKAGE DESCRIPTIO
5.23 (.206)
0.50 0.305 0.038 (.0197) (.0120 .0015) RECOMMENDED SOLDER LAYOUT
0.254 (.010) GAUGE PLANE
0.18 (.007) SEATING PLANE 0.17 0.27 (.007 .011) 0.127 0.076 (.005 .003)
MSOP (MS) 0603
NOTE: DIMENSIONS MILLIMETER/(INCH) DRAWING SCALE DIMENSION DOES INCLUDE MOLD FLASH, PROTRUSIONS GATE BURRS. MOLD FLASH, PROTRUSIONS GATE BURRS SHALL EXCEED 0.152mm (.006") SIDE DIMENSION DOES INCLUDE INTERLEAD FLASH PROTRUSIONS. INTERLEAD FLASH PROTRUSIONS SHALL EXCEED 0.152mm (.006") SIDE LEAD COPLANARITY (BOTTOM LEADS AFTER FORMING) SHALL 0.102mm (.004")
Package 10-Lead Plastic MSOP
(Reference 05-08-1661)
0.889 0.127 (.035 .005) 3.20 3.45 (.126 .136)
3.00 0.102 (.118 .004) (NOTE
0.497 0.076 (.0196 .003)
DETAIL
4.90 0.152 (.193 .006)
3.00 0.102 (.118 .004) (NOTE
0.53 0.152 (.021 .006)
DETAIL 1.10 (.043)
0.86 (.034)
0.50 (.0197)
3420fb
LT3420/LT3420-1
PACKAGE DESCRIPTIO
Package 10-Lead Plastic (3mm 3mm)
(Reference 05-08-1699)
0.675 ±0.05 PACKAGE OUTLINE 0.25 0.05 0.50 2.38 ±0.05 SIDES) RECOMMENDED SOLDER PITCH DIMENSIONS 0.115 0.38 0.10 3.00 ±0.10 SIDES) MARK (SEE NOTE 0.200 0.75 ±0.05 2.38 ±0.10 SIDES) BOTTOM VIEW-EXPOSED NOTE: DRAWING MADE JEDEC PACKAGE OUTLINE M0-229 VARIATION (WEED-2). CHECK WEBSITE DATA SHEET CURRENT STATUS VARIATION ASSIGNMENT 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 0.25 0.05 0.50 1.65 0.10 SIDES)
(DD10) 1103
3.50 ±0.05 1.65 ±0.05 2.15 ±0.05 SIDES)
0.00 0.05
3420fb
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.
LT3420/LT3420-1
TYPICAL APPLICATIO
VBAT 1.8V 4.7µF
LT3420-1 Photoflash Circuit Uses Tiny (3mm Tall) Transformer
1:10.2
DANGER HIGH VOLTAGE OPERATION HIGH VOLTAGE TRAINED PERSONEL ONLY 2.5V 4.7µF 60.4k VBAT LT3420-1 CHARGE DONE 0.1µF 4.7µF, X7R, 6.3V RUBYCON 100µF PHOTOFLASH CAPACITOR LDT565630T-002 FLYBACK TRANSFORMER VISHAY GSD2004S SOT-23 DUAL DIODE. DIODES CONNECTED SERIES RREF
TIME
CHARGE DONE
RELATED PARTS
PART NUMBER LTC®3400/LTC3400B LTC3401/LTC3402 LTC3405/LTC3405A LTC3406/LTC3406B LTC3407 LTC3411 LTC3425 LTC3440/LTC3441 LT3464 DESCRIPTION 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 1A/2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converters 300mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converters 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converters Dual 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 1.25A (IOUT), 4MHz, Synchronous Step-Down DC/DC Converter (ISW), 8MHz, Multiphase Synchronous Step-Up DC/DC Converter 600mA/1A (IOUT), 2MHz/1MHz, Synchronous Buck-Boost DC/DC Converters 85mA (ISW), Constant Off-Time, High Efficiency Step-Up DC/DC Converter with Integrated Schottky Output Disconnect 1.1A (ISW), 1.3MHz, High Efficiency Step-Up DC/DC Converter Photoflash Capacitor Charger ThinSOT COMMENTS 0.85V VOUT(MAX) 19µA/300µA, <1µA, ThinSOTPackage 0.5V VOUT(MAX) 38µA, <1µA, Package Efficiency, 2.7V VOUT(MIN) 0.8V 20µA, <1µA, ThinSOT Package Efficiency, 2.5V 5.5V, VOUT(MIN) 0.6V, 20µA, <1µA, ThinSOT Package Efficiency, 2.5V 5.5V, VOUT(MIN) 0.6V, 40µA, <1µA, ThinSOT Package Efficiency, 2.5V 5.5V, VOUT(MIN) 0.8V, 60µA, <1µA, Package Efficiency, 0.5V 4.5V, VOUT(MIN) 5.25V, 12µA, <1µA, Package Efficiency, 2.5V 5.5V, VOUT(MIN) 2.5V, 25µA, <1µA, Package 2.3V 10V, VOUT(MAX) 34V, 25µA, <0.5µA, ThinSOT Package 2.4V 16V, VOUT(MAX) 40V, 1.2mA, <1µA, ThinSOT Package Fast Photoflash Charge Times; 4.6sec LT3468, 5.5sec LT3468-1, 5.7sec LT3468-2
3420fb
LTC3467 LTC3468/LTC3468-1/ LTC3468-2
ThinsSOT trademark Linear Technology Corporation.
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, 95035-7417
(408) 432-1900
FAX: (408) 434-0507 www.linear.com
320V
Charge Time
VOUT CHARGED FROM 320V
100µF 330V PHOTOFLASH CAPACITOR
COUT 100µF COUT 40µF
3420 TA04
VBAT
3420 TA05
LT/LT 0305 PRINTED
LINEAR TECHNOLOGY CORPORATION 2002
Other recent searches
XDUR46C - XDUR46C XDUR46C Datasheet
SP8808 - SP8808 SP8808 Datasheet
DS2113 - DS2113 DS2113 Datasheet
SML100S11 - SML100S11 SML100S11 Datasheet
SHD124623 - SHD124623 SHD124623 Datasheet
SHD124623P - SHD124623P SHD124623P Datasheet
SHD124623N - SHD124623N SHD124623N Datasheet
SHD124623D - SHD124623D SHD124623D Datasheet
SC3045B - SC3045B SC3045B Datasheet
MDT2520-CH - MDT2520-CH MDT2520-CH Datasheet
CDA0867 - CDA0867 CDA0867 Datasheet
Privacy Policy | Disclaimer
© 2012 Datasheet Archive
