lt3573 Linear Technology Corporation, lt3573 Datasheet
lt3573
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lt3573 Summary of contents
Page 1
... A 1.25A, 60V NPN power switch is integrated along with all control logic into a 16- lead MSOP package. The LT3573 operates with input supply voltages from 3V to 40V, and can deliver output power with no external power devices.The LT3573 utilizes boundary mode operation to provide a small magnetic solution with improved load regulation ...
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... ............................................... REF ILIM Maximum Junction Temperature........................... 125°C Operating Junction Temperature Range (Note 2) LT3573E .............................................–40°C to 125°C Storage Temperature Range ...................–65°C to 150°C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LT3573EMSE#PBF LT3573EMSE#TRPBF LT3573IMSE#PBF LT3573IMSE#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. ...
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... Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3573E is guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage 5 ...
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... LT3573 TYPICAL PERFORMANCE CHARACTERISTICS Switch V CESAT 400 350 25°C 300 125°C 250 –50°C 200 150 100 0.25 0.50 0.75 1.00 1.25 SWITCH CURRENT (A) 3573 G04 SHDN/UVLO Falling Threshold 1.28 1.26 1.24 1.22 1.20 1.18 –60 –40 –20 0 TEMPERATURE (°C) 4 Switch Current Limit 1.8 MAXIMUM CURRENT LIMIT 1.6 1.4 1.2 1.0 RILIM = 10k 0.8 0.6 0.4 MINIMUM CURRENT LIMIT ...
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... This pin must be locally bypassed with a capacitor. BIAS: Bias Voltage. This pin supplies current to the switch driver and internal circuitry of the LT3573. This pin must be locally bypassed with a capacitor. This pin may also be connected third winding is not used and ≤ ...
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... LT3573 BLOCK DIAGRAM CURRENT REF R4 BIAS C5 1.22V R1 SHDN/UVLO R2 2.5μ FLYBACK Q2 ERROR CURRENT AMP COMPARATOR – g – 1.22V A1 + 20μA + INTERNAL A5 – REFERENCE I1 AND 7μA REGULATORS OUT L1A L1B C2 V OUT N:1 SW – ...
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... Boundary mode also allows the use of a smaller transformer compared to continuous conduction mode and no subharmonic oscillation. At low output currents the LT3573 delays turning on the switch, and thus operates in discontinuous mode. Unlike a traditional fl yback converter, the switch has to turn on to update the output voltage information ...
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... R REF can be found. They are external resistors used to program the output voltage. The LT3573 operates much the same way as traditional current mode switchers, the major difference being a different type of error amplifi er which derives its feedback information from the fl yback pulse. ...
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... LT3573 operation. Minimum Current Limit The LT3573 obtains output voltage information from the SW pin when the secondary winding conducts current. The sampling circuitry needs a minimum amount of time to sample the output voltage. To guarantee enough time, a minimum inductance value must be maintained ...
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... LT3573 APPLICATIONS INFORMATION Table 2. Common Resistor Values for 2:1 Transformers V ( (kΩ) OUT PS FB 3.3 2.00 37 2.00 130 15 2.00 162 Table 3. Common Resistor Values for 3:1 Transformers V ( (kΩ) OUT PS FB 3.3 3.00 56.2 5 3.00 80.6 10 3.00 165 Table 4. Common Resistor Values for 4:1 Transformers V ( (kΩ) OUT ...
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... L11-0059 9.52 9.52 4.95 L10-1019 9.52 9.52 4.95 Linear Technology has worked with several leading mag- netic component manufacturers to produce pre-designed fl yback transformers for use with the LT3573. Table 5 shows the details of several of these transformers PRI LEAKAGE PRI (nH (mΩ ...
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... Linear Technology has worked with several magnetic component manufacturers to produce predesigned fl yback transformers for use with the LT3573. Table 5 shows the details of several of these transformers. 12 Leakage Inductance ...
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... Figure 6. Good Snubber Diode Limits SW Pin Voltage V < 60V < 55V < 50V Figure 5. Maximum Voltages for SW Pin Flyback Waveform 10V/DIV 3573 F06 Figure 7. Bad Snubber Diode Does Not Limit SW Pin Voltage LT3573 SW t > 350ns OFF TIME t < 150ns 3573 F05 SP 3573 F07 ...
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... V IN UVLO FALLING ( To implement external run/stop control, connect a small NMOS to the UVLO pin, as shown in Figure 8. Turning the NMOS on grounds the UVLO pin and prevents the LT3573 from operating, and the part will draw less than a 1μA of quiescent current plot in the Typical Per- ILIM as shown in Figure 8 ...
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... For proper operation of the LT3573 winding is used as a supply for the BIAS pin, ensure that the BIAS pin voltage is at least 3.15V and always less than the input voltage. ...
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... The turns ratio is then selected as primary: secondary: BIAS = 3:1:1. 2. Select the transformer primary inductance for target switching frequency. The LT3573 requires a minimum amount of time to sample the output voltage during the off-time. This off-time shall be greater than 350ns over all operating OFF(MIN) conditions ...
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... Soft-start capacitor helps during the start-up of the fl yback converter. Select the UVLO resistor divider for intended input opera- tion range. These equations are aforementioned LT3573 is selected as 6.04k. REF fi lters out the noise REF to lower the current ...
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... T1: PULSE PA2454NL OR WÜRTH ELEKTRONIK 750310471 C2 C3 D1: B340A 10nF 1000pF D2: 1N4148 C5: MURATA, GRM32ER71A476K 3573 TA02 ±12V Isolated Flyback Converter C6 R8 0.22 μ SHDN/UVLO D3 R3 118k R FB LT3573 R REF R4 6.04k ILIM GND TEST BIAS R7 56. 10nF 3300pF T1: COILTRONICS VPH1-0076-R ...
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... C5: MURATA, GRM32ER71A476K Effi ciency 24V 12V 200 400 600 800 1000 1200 1400 I (mA) OUT 3573 TA04b LT3573 D1 + 3:1:1 V OUT 5V, 700mA 2.6 μ μ μ F – V OUT D3 D2 *OPTIONAL THIRD WINDING FOR L1C 40V OPERATION 2 ...
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... BIAS D2 R7 25. L1C 4.7μF 10nF 1500pF 1.5 T1: PULSE PA2362NL OR COILCRAFT GA3429-BL D1: B340A D3: 1N4148 12V Isolated Flyback Converter C6 R8 0.22 μ SHDN/UVLO R3 178k LT3573 REF R4 6.04k TC R ILIM GND TEST BIAS R7 40. 10nF 4700pF T1: COILTRONICS VP1-0102-R D1: B340A D2: 1N4148 D1 ...
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... V IN SHDN/UVLO R2 90.9k LT3573 REF TC R ILIM GND TEST BIAS R7 R5 47.5k 30k 10nF 1000pF T1: BH ELECTRONICS L11-0059 D1: B340A D2: 1N4148 LT3573 + 2:1:1:1:1 V OUT1 12V, 60mA 10.9 μ H 43.6 μ μ – V OUT1 OUT2 12V, 60mA D2 C6 10.9 μ ...
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... ILIM GND TEST BIAS R7 56. 10nF 1500pF T1: BH ELECTRONICS, L10-1022 D1: B220A D2: CMD5H-3 300V Isolated Flyback Converter C6 V 0.22 μ IN SHDN/UVLO R3 90.9k LT3573 REF R4 6.04k TC R ILIM GND TEST BIAS R7 10k 10nF 1000pF D1: TOSHIBA CRF02 D2: ZETEX ZHCS 506TA D1 ...
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... DETAIL “A” 1.10 (.043) MAX SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3573 8 0.35 REF 1.651 0.102 0.12 REF (.065 .004) DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY 9 NO MEASUREMENT PURPOSE 0 ...
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... Burst Mode is a registered trademark of Linear Technology Corporation Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 30V , +5V/–5V Isolated Flyback Converter IN OUT C6 V 0.22 μ SHDN/UVLO R3 LT3573 80. REF R4 TC 6.04k R ILIM GND TEST BIAS D3 R7 23.7k ...