LTC Constant Frequency Current Mode Flyback DC/DC Controller in ThinSOT FEATURES DESCRIPTION

Transcription

1 FEATURES n IN and OUT Limited Ony by Externa Components n.8 Undervotage Lockout Threshod n Operating Junction Temperature from 55 C to 50 C n Adjustabe Sope Compensation n Interna Soft-Start n Constant Frequency 200kHz Operation n ±.5% Reference Accuracy n Current Mode Operation for Exceent Line and Load Transient Response n No Minimum Load Requirement n Low Quiescent Current: 20μA n Low Profi e (mm) SOT-23 Package APPLICATIONS n 2 and 2 Automotive Power Suppies n Teecom Power Suppies n Auxiiary/Housekeeping Power Suppies n Power Over Ethernet L, LT, LTC, LTM, Burst Mode, Linear Technoogy and the Linear ogo are registered trademarks and ThinSOT and No R SENSE are trademarks of Linear Technoogy Corporation. A other trademarks are the property of their respective owners. DESCRIPTION Constant Frequency Current Mode Fyback DC/DC Controer in ThinSOT The LTC is a constant frequency current mode fyback controer optimized for driving N-channe MOSFETs in high input votage appications. The operates from inputs as ow as 5. Constant frequency operation is maintained down to very ight oads, resuting in ess ow frequency noise generation over a wide range of oad currents. Sope compensation can be programmed with an externa resistor. The provides ±.5% output votage accuracy and consumes ony 20μA of quiescent current. Groundreferenced current sensing aows -based converters to accept input suppies beyond the s absoute maximum CC. For simpicity, the can be powered from a high IN through a resistor, due to its interna shunt reguator. An interna undervotage ockout shuts down the IC when the input votage is too ow to provide sufficient gate drive to the externa MOSFET. The is avaiabe in a ow profi e (mm) 6-ead SOT-23 (ThinSOT ) package. TYPICAL APPLICATION 0nF 8.06k IN 6 TO 50 PDZ6.8B 7.5k Dua Output Wide Input Range Converter 22k I TH /RUN NGATE GND CC FB SENSE 57.6k 0.μF ALL CAPACITORS ARE X7R, TDK.7k μf 00 3 MMBTA2 PHM25NQ0T 0.02Ω PH5-055 μf 00 μf 00 0MQ00N B300 3/0.3A 20mA MIN LOAD 22μF 0 7μF 0 6.5/.2A TA0 EFFICIENCY (%) IN = Effi ciency and Power Loss vs Output Power IN = 2 IN = 2 IN = 8 IN = OUTPUT POWER (W) POWER LOSS (W) TA0b

2 ABSOLUTE MAXIMUM RATINGS (Note ) CC to GND (Current Fed)... 25mA into CC * NGATE otage to CC FB, I TH /RUN otages to 3.5 SENSE otage to NGATE Peak Output Current (<0μs)... A Operating Junction Temperature Range (Notes 2, 3) LTC3803E C to 25 C LTC3803I C to 25 C LTC3803H-5 (Note 3)... 0 C to 50 C LTC3803MP-5 (Note 3) C to 50 C Storage Temperature Range C to 50 C Lead Temperature (Sodering, 0 sec) C * interna camp circuit sef reguates CC votage to 8.. PIN CONFIGURATION I TH /RUN GND 2 FB 3 TOP IEW 6 NGATE 5 CC SENSE S6 PACKAGE 6-LEAD PLASTIC TSOT-23 T JMAX = 50 C, θ JA = 92 C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3803ES6-5#PBF LTC3803ES6-5#TRPBF LTBPF 6-Lead Low Profi e (mm) SOT-23 0 C to 25 C LTC3803IS6-5#PBF LTC3803IS6-5#TRPBF LTBMH 6-Lead Low Profi e (mm) SOT-23 0 C to 25 C LTC3803HS6-5#PBF LTC3803HS6-5#TRPBF LTBMH 6-Lead Low Profi e (mm) SOT-23 0 C to 50 C LTC3803MPS6-5#PBF LTC3803MPS6-5#TRPBF LTBMH 6-Lead Low Profi e (mm) SOT C to 50 C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3803ES6-5 LTC3803ES6-5#TR LTBPF 6-Lead Low Profi e (mm) SOT-23 0 C to 25 C LTC3803IS6-5 LTC3803IS6-5#TR LTBMH 6-Lead Low Profi e (mm) SOT-23 0 C to 25 C LTC3803HS6-5 LTC3803HS6-5#TR LTBMH 6-Lead Low Profi e (mm) SOT-23 0 C to 50 C LTC3803MPS6-5 LTC3803MPS6-5#TR LTBMH 6-Lead Low Profi e (mm) SOT C to 50 C Consut LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a abe on the shipping container. For more information on ead free part marking, go to: For more information on tape and ree specifi cations, go to: ELECTRICAL CHARACTERISTICS The denotes the specifi cations which appy over the fu operating junction temperature range, otherwise specifi cations are at T A = 25 C. CC = 5, uness otherwise noted. (Notes 2, 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS TURNON CC Turn On otage LTC3803E-5 LTC3803I-5, LTC3803H-5, LTC3803MP-5 TURNOFF CC Turn Off otage LTC3803E-5 LTC3803I-5, LTC3803H-5, LTC3803MP-5 HYST CC Hysteresis TURNON TURNOFF CLAMPmA CC Shunt Reguator otage at ma I CC = ma, ITH/RUN = 0 LTC3803E-5 LTC3803I-5, LTC3803H-5 LTC3803MP

3 ELECTRICAL CHARACTERISTICS The denotes the specifi cations which appy over the fu operating junction temperature range, otherwise specifi cations are at T A = 25 C. CC = 5, uness otherwise noted. (Notes 2, 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS CLAMP25mA CC Shunt Reguator otage at 25mA I CC = 25mA, ITH/RUN = 0 LTC3803E-5 LTC3803I-5, LTC3803H-5 LTC3803MP-5 I CC I CC,(U) Input DC Suppy Current in Norma Operation Input DC Suppy Current in Undervotage (Note ) ITH/RUN = μa CC = TURNON 00m LTC3803E-5 LTC3803I-5, LTC3803H-5, LTC3803MP-5 ITHSHDN Shutdown Threshod (at I TH /RUN) CC > TURNON, ITH/RUN Faing LTC3803E-5 LTC3803I-5, LTC3803H-5 LTC3803MP-5 I ITHSTART Start-Up Current Source ITH/RUN = 0 LTC3803E-5 LTC3803I-5, LTC3803H-5, LTC3803MP-5 FB Reguated Feedback otage (Note 5) LTC3803E-5: 0 C T J 85 C 0 C T J 85 C LTC3803I-5: 0 C T J 85 C 0 C T J 25 C LTC3803H-5: 0 C T J 85 C 0 C T J 50 C LTC3803MP-5: 0 C T J 85 C 55 C T J 50 C g m Error Ampifi er Transconductance I TH/RUN Pin Load = ±5μA (Note 5) μa/ Δ O(LINE) Output otage Line Reguation (Note 5) 0. m/ Δ O(LOAD) Output otage Load Reguation I TH/RUN Sinking 5μA (Note 5) I TH/RUN Sourcing 5μA (Note 5) μa μa μa μa m/μa m/μa I FB FB Input Current (Note 5) 0 50 na f OSC Osciator Frequency ITH/RUN = khz DC ON(MIN) Minimum Switch On Duty Cyce ITH/RUN =.3, FB = % DC ON(MAX) Maximum Switch On Duty Cyce ITH/RUN =.3, FB = % t RISE Gate Drive Rise Time C LOAD = 3000pF 0 ns t FALL Gate Drive Fa Time C LOAD = 3000pF (Note 7) 0 ns IMAX Peak Current Sense otage R SL = 0 (Note 6) LTC3803E-5 LTC3803I-5, LTC3803H-5 LTC3803MP-5 I SLMAX Peak Sope Compensation Output Current (Note 7) 5 μa t SFST Soft-Start Time 0.7 ms m m m 3

4 ELECTRICAL CHARACTERISTICS Note : Stresses beyond those isted under Absoute Maximum Ratings may cause permanent damage to the device. Exposure to any Absoute Maximum Rating condition for extended periods may affect device reiabiity and ifetime. Note 2: The is tested under pused oad conditions such that T J T A. The LTC3803E-5 is guaranteed to meet specifi cations from 0 C to 85 C junction temperature. Specifi cations over the 0 C to 25 C operating junction temperature range are assured by design, characterization and correation with statistica process contros. The LTC3803I-5 is guaranteed over the 0 C to 25 C operating junction temperature range, the LTC3803H-5 is guaranteed over the 0 C to 50 C operating junction temperature range and the LTC3803MP-5 is tested and guaranteed over the fu 55 C to 50 C operating junction temperature range. Note that the maximum ambient temperature consistent with these specifi cations is determined by specifi c operating conditions in conjunction with board ayout, the rated package therma impedance and other environmenta factors. Junction temperature (T J ) is cacuated from the ambient temperature T A and the power dissipation P D in the using the formua: T J = T A + (P D 230 C/W) Note 3: High junction temperatures degrade operating ifetimes; operating ifetime is derated for junction temperatures greater than 25 C. Note : Dynamic suppy current is higher due to the gate charge being deivered at the switching frequency. Note 5: The is tested in a feedback oop that servos FB to the output of the error ampifi er whie maintaining I TH /RUN at the midpoint of the current imit range. Note 6: Peak current sense votage is reduced dependent on duty cyce and an optiona externa resistor in series with the SENSE pin (R SL ). For detais, refer to the programmabe sope compensation feature in the Appications Information section. Note 7: Guaranteed by design. TYPICAL PERFORMANCE CHARACTERISTICS FB OLTAGE (m) Reference otage vs Temperature 820 CC = FB OLTAGE (m) Reference otage vs Suppy otage T A = 25 C CC CLAMPmA FB OLTAGE (m) 82 TA = 25 C Reference otage vs CC Shunt Reguator Current CC SUPPLY OLTAGE () I CC (ma) G G G03 OSCILLATOR FREQUENCY (khz) Osciator Frequency vs Temperature CC = 5 OSCILLATOR FREQUENCY (khz) Osciator Frequency vs Suppy otage T A = 25 C OSCILLATOR FREQUENCY (khz) Osciator Frequency vs CC Shunt Reguator Current T A = 25 C CC SUPPLY OLTAGE () I CC (ma) G G G06

5 TYPICAL PERFORMANCE CHARACTERISTICS CC Undervotage Lockout Threshods vs Temperature CC Shunt Reguator otage vs Temperature I CC Suppy Current vs Temperature CC = 5 ITH/RUN =.3 OLTS TURNON TURNOFF CC () I CC = 25mA I CC = ma SUPPLY CURRENT (μa) G G G09 START-UP SUPPLY CURRENT (μa) Start-Up I CC Suppy Current vs Temperature CC = TURNON 0. SHUTDOWN THRESHOLD (m) I TH /RUN Shutdown Threshod vs Temperature I TH /RUN PIN CURRENT SOURCE (na) I TH /RUN Start-Up Current Source vs Temperature CC = TURNON + 0. ITH/RUN = G G G2 Peak Current Sense otage vs Temperature Soft-Start Time vs Temperature 20 5 CC = 5..2 CC = 5 SENSE PIN OLTAGE (m) SOFT-START TIME (ms) G G 5

6 PIN FUNCTIONS I TH /RUN (Pin ): This pin performs two functions. It serves as the error ampifi er compensation point as we as the run/shutdown contro input. Nomina votage range is 0.7 to.9. Forcing this pin beow the shutdown threshod ( ITHSHDN ) causes the to shut down. In shutdown mode, the NGATE pin is hed ow. GND (Pin 2): Ground Pin. FB (Pin 3): Receives the feedback votage from an externa resistive divider across the output. SENSE (Pin ): This pin performs two functions. It monitors switch current by reading the votage across an externa current sense resistor to ground. It aso injects a current ramp that deveops sope compensation votage across an optiona externa programming resistor. CC (Pin 5): Suppy Pin. Must be cosey decouped to GND (Pin 2). NGATE (Pin 6): Gate Drive for the Externa N-channe MOSFET. This pin swings from 0 to CC. BLOCK DIAGRAM 5 CC 800m REFERENCE CC SHUNT REGULATOR 0.3μA SHUTDOWN COMPARATOR CC < TURNON UNDEROLTAGE LOCKOUT SOFT- START CLAMP SHUTDOWN 3 FB + ERROR AMPLIFIER + CURRENT COMPARATOR R S Q SWITCHING LOGIC AND BLANKING CIRCUIT CC GATE DRIER NGATE 6 2 GND.2 20m 200kHz OSCILLATOR SLOPE COMP CURRENT RAMP I TH /RUN SENSE BD 6

7 OPERATION The is a constant frequency current mode controer for fyback, SEPIC and DC/DC boost converter appications in a tiny ThinSOT package. The is designed so that none of its pins need to come in contact with the input or output votages of the power suppy circuit of which it is a part, aowing the conversion of votages we beyond the s absoute maximum ratings. Main Contro Loop Due to space imitations, the basics of current mode DC/DC conversion wi not be discussed here; instead, the reader is referred to the detaied treatment in Appication Note 9, or in texts such as Abraham Pressman s Switching Power Suppy Design. Pease refer to the Bock Diagram and the Typica Appication on the front page of this data sheet. An externa resistive votage divider presents a fraction of the output votage to the FB pin. The divider must be designed so that when the output is at the desired votage, the FB pin votage wi equa the 800m from the interna reference. If the oad current increases, the output votage wi decrease sighty, causing the FB pin votage to fa beow 800m. The error ampifi er responds by feeding current into the I TH /RUN pin. If the oad current decreases, the FB votage wi rise above 800m and the error ampifi er wi sink current away from the I TH /RUN pin. The votage at the I TH /RUN pin commands the puse-width moduator formed by the osciator, current comparator and RS atch. Specificay, the votage at the I TH /RUN pin sets the current comparator s trip threshod. The current comparator monitors the votage across a current sense resistor in series with the source termina of the externa MOSFET. The turns on the externa power MOSFET when the interna free-running 200kHz osciator sets the RS atch. It turns off the MOSFET when the current comparator resets the atch or when 80% duty cyce is reached, whichever happens first. In this way, the peak current eves through the fyback transformer s primary and secondary are controed by the I TH /RUN votage. Since the I TH /RUN votage is increased by the error ampifier whenever the output votage is beow nomina, and decreased whenever output votage exceeds nomina, the votage reguation oop is cosed. For exampe, whenever the oad current increases, output votage wi decrease sighty, and sensing this, the error ampifi er raises the I TH /RUN votage by sourcing current into the I TH /RUN pin, raising the current comparator threshod, thus increasing the peak currents through the transformer primary and secondary. This deivers more current to the oad, bringing the output votage back up. The I TH /RUN pin serves as the compensation point for the contro oop. Typicay, an externa series RC network is connected from I TH /RUN to ground and is chosen for optima response to oad and ine transients. The impedance of this RC network converts the output current of the error ampifier to the I TH /RUN votage which sets the current comparator threshod and commands considerabe infuence over the dynamics of the votage reguation oop. Start-Up/Shutdown The has two shutdown mechanisms to disabe and enabe operation: an undervotage ockout on the CC suppy pin votage, and a forced shutdown whenever externa circuitry drives the I TH /RUN pin ow. The transitions into and out of shutdown according to the state diagram (Figure ). CC < TURNOFF (NOMINALLY ) SHUT DOWN ENABLED ITH/RUN < ITHSHDN (NOMINALLY 0.28) F0 Figure. Start-Up/Shutdown State Diagram ITH/RUN > ITHSHDN AND CC > TURNON (NOMINALLY.8) 7

8 OPERATION The undervotage ockout (ULO) mechanism prevents the from trying to drive a MOSFET with insufficient GS. The votage at the CC pin must exceed TURNON (nominay.8) at east momentariy to enabe operation. The CC votage is then aowed to fa to TURNOFF (nominay ) before undervotage ockout disabes the. The I TH /RUN pin can be driven beow ITHSHDN (nominay 0.28) to force the into shutdown. An interna 0.3μA current source aways tries to pu this pin towards CC. When the I TH /RUN pin votage is aowed to exceed ITHSHDN, and CC exceeds TURNON, the begins to operate and an interna camp immediatey pus the I TH /RUN pin up to about 0.7. In operation, the I TH /RUN pin votage wi vary from roughy 0.7 to.9 to represent current comparator threshods from zero to maximum. Interna Soft-Start An interna soft-start feature is enabed whenever the comes out of shutdown. Specificay, the I TH / RUN votage is camped and is prevented from reaching maximum unti roughy 0.7ms has passed. This aows the input and output currents of -based power suppies to rise in a smooth and controed manner on start-up. Powering the In the simpest case, the can be powered from a high votage suppy through a resistor. A buit-in shunt reguator from the CC pin to GND wi draw as much current as needed through this resistor to reguate the CC votage to around 8. as ong as the CC pin is not forced to sink more than 25mA. This shunt reguator is aways active, even when the is in shutdown, since it serves the vita function of protecting the CC pin from seeing too much votage. The CC pin must be bypassed to ground immediatey adjacent to the IC pins with a ceramic or tantaum capacitor. Proper suppy bypassing is necessary to suppy the high transient currents required by the MOSFET gate driver. 0μF is a good starting point. Adjustabe Sope Compensation The injects a 5μA peak current ramp out through its SENSE pin which can be used for sope compensation in designs that require it. This current ramp is approximatey inear and begins at zero current at 6.5% duty cyce, reaching peak current at 80% duty cyce. Additiona detais are provided in the Appications Information section. 8

9 APPLICATIONS INFORMATION Many appication circuits can be derived from the topoogy shown in Figure 2. The itsef imposes no imits on aowed power output, input votage IN or desired reguated output votage OUT ; these are a determined by the ratings on the externa power components. The key factors are: Q s maximum drain-source votage (B DSS ), on-resistance (R DS(ON) ) and maximum drain current, T s saturation f ux eve and winding insuation breakdown votages, C IN and C OUT s maximum working votage, ESR, and maximum rippe current ratings, and D and R SENSE s power ratings. C CC C C 2 R CC CC I TH /RUN NGATE GND SENSE FB R IN Figure 2. Typica Appication Circuit SELECTING FEEDBACK RESISTOR DIIDER ALUES The reguated output votage is determined by the resistor divider across OUT (R and R2 in Figure 2). The ratio of R2 to R needed to produce a desired OUT can be cacuated: R2= OUT R2 6 R C IN T L PRI R SL Q D L SEC R SENSE C OUT F02 OUT Choose resistance vaues for R and R2 to be as arge as possibe in order to minimize any effi ciency oss due to the static current drawn from OUT, but just sma enough so that when OUT is in reguation, the error caused by the nonzero input current to the FB pin is ess than %. A good rue of thumb is to choose R to be 80k or ess. TRANSFORMER DESIGN CONSIDERATIONS Transformer specification and design is perhaps the most critica part of appying the successfuy. In addition to the usua ist of caveats deaing with high frequency power transformer design, the foowing shoud prove usefu. Turns Ratios Due to the use of the externa feedback resistor divider ratio to set output votage, the user has reative freedom in seecting transformer turns ratio to suit a given appication. Simpe ratios of sma integers, e.g., :, 2:, 3:2, etc. can be empoyed which yied more freedom in setting tota turns and mutua inductance. Simpe integer turns ratios aso faciitate the use of off-the-shef configurabe transformers such as the Coitronics ERSA-PAC series in appications with high input to output votage ratios. For exampe, if a 6-winding ERSA-PAC is used with three windings in series on the primary and three windings in parae on the secondary, a 3: turns ratio wi be achieved. Turns ratio can be chosen on the basis of desired duty cyce. However, remember that the input suppy votage pus the secondary-to-primary referred version of the fyback puse (incuding eakage spike) must not exceed the aowed externa MOSFET breakdown rating. 9

10 APPLICATIONS INFORMATION Leakage Inductance Transformer eakage inductance (on either the primary or secondary) causes a votage spike to occur after the output switch (Q) turn-off. This is increasingy prominent at higher oad currents, where more stored energy must be dissipated. In some cases a snubber circuit wi be required to avoid overvotage breakdown at the MOSFET s drain node. Appication Note 9 is a good reference on snubber design. A bifi ar or simiar winding technique is a good way to minimize troubesome eakage inductances. However, remember that this wi imit the primary-to-secondary breakdown votage, so bifiar winding is not aways practica. CURRENT SENSE RESISTOR CONSIDERATIONS The externa current sense resistor (R SENSE in Figure 2) aows the user to optimize the current imit behavior for the particuar appication. As the current sense resistor is varied from severa ohms down to tens of miiohms, peak switch current goes from a fraction of an ampere to severa amperes. Care must be taken to ensure proper circuit operation, especiay with sma current sense resistor vaues. For exampe, a peak switch current of 5A requires a sense resistor of 0.020Ω. Note that the instantaneous peak power in the sense resistor is 0.5W and it must be rated accordingy. The has ony a singe sense ine to this resistor. Therefore, any parasitic resistance in the ground side connection of the sense resistor wi increase its apparent vaue. In the case of a 0.020Ω sense resistor, one miiohm of parasitic resistance wi cause a 5% reduction in peak switch current. So the resistance of printed circuit copper traces and vias cannot necessariy be ignored. PROGRAMMABLE SLOPE COMPENSATION The injects a ramping current through its SENSE pin into an externa sope compensation resistor (R SL in Figure 2). This current ramp starts at zero right after the NGATE pin has been high for the s minimum duty cyce of 6.5%. The current rises ineary towards a peak of 5μA at the maximum duty cyce of 80%, shutting off once the NGATE pin goes ow. A series resistor (R SL ) connecting the SENSE pin to the current sense resistor (R SENSE ) thus deveops a ramping votage drop. From the perspective of the SENSE pin, this ramping votage adds to the votage across the sense resistor, effectivey reducing the current comparator threshod in proportion 0

11 APPLICATIONS INFORMATION to duty cyce. This stabiizes the contro oop against subharmonic osciation. The amount of reduction in the current comparator threshod (Δ SENSE ) can be cacuated using the foowing equation: Duty Cyce 6.5% Δ SENSE = 5μAR SL 73.5% Note: enforces 6.5% < Duty Cyce < 80%. A good starting vaue for R SL is 5.9k, which gives a 30m drop in current comparator threshod at 80% duty cyce. Designs not needing sope compensation may repace R SL with a short circuit. GND to drop enough votage across R CC to reguate CC to around 8.. For appications where IN is ow enough such that the static power dissipation in R CC is acceptabe, using the CC shunt reguator is the simpest way to power the. EXTERNAL PREREGULATOR The circuit in Figure shows another way to power the. An externa series prereguator consisting of series pass transistor Q, Zener diode D, and bias resistor R B brings CC above the CC turn-on threshod, enabing the. CC SHUNT REGULATOR 8 TO 75 IN An interna shunt reguator aows the to be powered through a singe dropping resistor from IN to CC, in conjunction with a bypass capacitor, C CC, that cosey decoupes CC to GND (see Figure 3). The shunt reguator can draw up to 25mA through the CC pin to R B 00k D 6.8 Q MMBTA2 C CC 0.μF CC GND F0 IN R CC C CC CC GND Figure. Powering the with an Externa Prereguator F03 Figure 3. Powering the ia the Interna Shunt Reguator

12 TYPICAL APPLICATIONS 2W Isoated Housekeeping Teecom Converter PRIMARY SIDE 0, 00mA OUTPUT 220k MMBTA2 BAS56 T 2.2μF IN 36 TO 75 nf 787Ω 22k 9.09k 2 3 I TH /RUN NGATE GND FB PDZ6.8B BAS56 CC SENSE 30Ω 6 5 k 5.6k μf μf FDC252 0.Ω BAS56 2.2μF SECONDARY SIDE GROUND SECONDARY SIDE 0, 00mA OUTPUT T: PULSE ENGINEERING PA068 OR TYCO TTI8698 PRIMARY GROUND TA03 2

13 TYPICAL APPLICATIONS : Input Range 3.3 Output Isoated Fyback DC/DC Converter + IN 8 TO 72 IN 2.2μF 220k MMBTA2 T PA277NL PDS00 00μF OUT A GND PDZ6.8B 68Ω BAS56 30Ω 50pF CC 680Ω 22Ω BAS56 0Ω I TH /RUN GATE 6 FDC252 0.μF 2 GND CC 5 OUT + 3 FB SENSE.7k BAT760 0.μF 0.00Ω CC 270Ω BAS56 6.8k PS280-2 BAS56 0.μF μF 3 IN OPTO LT30 GND OC COMP FB nF 22.k 56k 7pF 00k OUT TA05 Effi ciency vs Load Current 8 82 EFFICIENCY (%) IN = 8 IN = I OUT (A) TA05a 3

14 PACKAGE DESCRIPTION S6 Package 6-Lead Pastic TSOT-23 (Reference LTC DWG # ) 0.62 MAX 0.95 REF 2.90 BSC (NOTE ).22 REF 3.85 MAX 2.62 REF. MIN 2.80 BSC (NOTE ) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.95 BSC PLCS (NOTE 3) BSC DATUM A.00 MAX REF (NOTE 3) NOTE:. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIE OF PLATING. DIMENSIONS ARE EXCLUSIE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.25mm 6. JEDEC PACKAGE REFERENCE IS MO BSC S6 TSOT RE B

15 REISION HISTORY (Revision history begins at Rev D) RE DATE DESCRIPTION PAGE NUMBER D 6/0 MP-grade part added. Ref ected throughout the data sheet. to 6 Information furnished by Linear Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Linear Technoogy Corporation makes no representation that the interconnection of its circuits as described herein wi not infringe on existing patent rights. 5

16 TYPICAL APPLICATION Synchronous Fyback Converter IN 36 TO k PDZ6.8B MMBTA2 30Ω C IN T Q2 OUT * 3.3.5A C O n 33k 2 I TH /RUN GATE GND CC Q D 0.μF 8.06k k* R FB OUT FB SENSE μf 0 5k R CS TA0 T: PULSE ENGINEERING PA006 Q: FAIRCHILD FDC252 Q2: ISHAY Si9803 D: PHILIPS BAS56 C IN : TDK μf, 00, X5R C O : TDK 00μF, 6.3, X5R R CS : ISHAY OR IRC, 80mΩ *FOR 5 OUTPUT CHANGE R FB TO 2.2k RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT3573 Isoated Fyback Switching Reguator with 60 3 IN 0, No Opto-Isoator or Third Winding Required, Up to 7W Integrated Switch Output Power, MSOP-6E LTC3805/ LTC LTC3873/ LTC Adjustabe Constant Frequency Fyback, Boost, SEPIC DC/DC Controer No R SENSE Constant Frequency Fyback, Boost, SEPIC Controer IN and OUT Limited Ony by Externa Components, 3mm 3mm DFN-0, MSOP-0E Packages IN and OUT Limited Ony by Externa Components, 8-pin ThinSOT or 2mm 3mm DFN-8 Packages LT3757 Boost, Fyback, SEPIC and Inverting Controer 2.9 IN 0, 00kHz to MHz Programmabe Operating Frequency, 3mm 3mm DFN-0 and MSOP-0E Package LT3758 Boost, Fyback, SEPIC and Inverting Controer 5.5 IN 00, 00kHz to MHz Programmabe Operating Frequency, 3mm 3mm DFN-0 and MSOP-0E LTC87/LTC87-/ LTC87-7 Wide Input Range, No R SENSE Low Quiescent Current Fyback, Boost and SEPIC Controer Programmabe Operating Frequency, 2.5 IN 36, Burst Mode Operation at Light Load, MSOP-0 6 LT 060 RE D PRINTED IN USA Linear Technoogy Corporation 630 McCarthy Bvd., Mipitas, CA (08) FAX: (08) LINEAR TECHNOLOGY CORPORATION 200

17 Mouser Eectronics Authorized Distributor Cick to iew Pricing, Inventory, Deivery & Lifecyce Information: Anaog Devices Inc.: LTC3803HS6-5#PBF LTC3803ES6-5#TRPBF LTC3803ES6-5#TR LTC3803HS6-5 LTC3803HS6-5#TRM LTC3803IS6-5#TRMPBF LTC3803IS6-5#TRPBF LTC3803ES6-5#PBF LTC3803MPS6-5#TRPBF LTC3803IS6-5#PBF LTC3803MPS6-5#PBF LTC3803ES6-5#TRM LTC3803HS6-5#TR LTC3803ES6-5#TRMPBF LTC3803HS6-5#TRPBF LTC3803ES6-5 LTC3803HS6-5#TRMPBF LTC3803MPS6-5#TRMPBF