LT3758 LINER [Linear Technology], LT3758 Datasheet
LT3758
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LT3758 Summary of contents
Page 1
... The fi xed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages. The operating frequency of LT3758 can be set with an external resistor over a 100kHz to 1MHz range, and can be synchronized to an external clock using the SYNC pin. ...
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... LT3758IDD#PBF LT3758IDD#TRPBF LT3758EMSE#PBF LT3758EMSE#TRPBF LT3758IMSE #PBF LT3758IMSE#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ...
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... FBX = 1. 0V, Current Out of Pin Falling INTV CC UVLO Hysteresis V = 100V 20V IN 0 < I < 10mA INTVCC < V < 100V 6V 10mA IN INTVCC LT3758 MIN TYP MAX UNITS 5.5 100 V 0.1 1 μA 6 μA 1.6 2.2 mA 350 400 μA l 100 110 120 mV –65 μ ...
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... L CC LT3758I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note 3: The LT3758 is tested in a feedback loop which servos V reference voltages (1.6V and –0.8V) with the VC pin forced to 1.3V. Note 4: FBX overvoltage lockout is measured regulated V FBX(REG) Note 5: Rise and fall times are measured at 10% and 90% levels. ...
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... 125 75 100 0 100 200 3758 G03 Normalized Switching Frequency vs FBX 120 100 –0.8 1000 800 900 3758 G05 LT3758 T = 25°C, unless otherwise noted INTV = 5. 100V V = 24V IN IN 125 – 100 TEMPERATURE (° ...
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... LT3758 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency vs Temperature 325 R = 41.2k T 320 315 310 305 300 295 290 285 280 275 –50 – TEMPERATURE (°C) SENSE Current Limit Threshold vs Duty Cycle 115 110 105 100 DUTY CYCLE (%) SHDN/UVLO Current vs Voltage ...
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... Dropout Voltage CC vs Current, Temperature 900 125°C 800 700 600 500 400 300 200 100 INTV LOAD (mA) CC LT3758 T = 25°C, unless otherwise noted. A Minimum Output 125°C INTV = 4.7V CC INTV = 100 V (V) IN 3758 G14 Line Regulation CC ...
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... LT3758 TYPICAL PERFORMANCE CHARACTERISTICS Gate Drive Rise and Fall Time INTV = 7. RISE TIME (nF) L Typical Start-Up Waveforms V = 48V IN V OUT 10V/DIV L1A L1B 1A/DIV 2ms/DIV SEE TYPICAL APPLICATION: 18V TO 72V INPUT, 24V OUTPUT SEPIC CONVERTER ...
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... Input Supply Pin. Must be locally bypassed IN with a 0.22μ larger, capacitor placed close to the pin. Exposed Pad (Pin 11): Ground. This pin also serves as the negative terminal of the current sense resistor. The Exposed Pad must be soldered directly to the local ground plane. LT3758 CC can be connected CC can also CC 3758f 9 ...
Page 10
... A11 – 1.72V + G6 A12 – + –0.88V + 1.6V A1 – FBX FBX – –0.8V FREQUENCY FOLDBACK 3 Figure 1. LT3758 Block Diagram Working as a SEPIC Converter SHDN/UVLO A10 – 1.22V INTERNAL REGULATOR CURRENT AND UVLO I S2 17.5V + 10μA UVLO A9 7.2V LDO – ...
Page 11
... APPLICATIONS INFORMATION Main Control Loop The LT3758 uses a fi xed frequency, current mode control scheme to provide excellent line and load regulation. Op- eration can be best understood by referring to the Block Diagram in Figure 1. The start of each oscillator cycle sets the SR latch (SR1) and turns on the external power MOSFET switch M1 through driver G2. The switch current fl ...
Page 12
... Q = power MOSFET total gate charge G 12 The LT3758 uses packages with an Exposed Pad for en- hanced thermal conduction. With proper soldering to the Exposed Pad on the underside of the package and a full copper plane underneath the device, thermal resistance (θ ) will be about 43°C/W for the DD package and 40°C/W JA for the MSE package ...
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... RT pin to ground, as shown in Figure 1. The RT pin must have an external resistor to GND for proper operation of the LT3758. A table for selecting the value of R operating frequency is shown in Table 1. pin shorted to CC Table 1 ...
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... APPLICATIONS INFORMATION The operating frequency of the LT3758 can be synchronized to an external clock source. By providing a digital clock signal into the SYNC pin, the LT3758 will operate at the SYNC clock frequency. If this feature is used should be chosen to program a switching frequency 20% slower than SYNC pulse frequency. The SYNC pulse should have a minimum pulse width of 200ns ...
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... SENSE Pin Programming For control and protection, the LT3758 measures the power MOSFET current by using a sense resistor (R between GND and the MOSFET source. Figure 4 shows a typical waveform of the sense voltage (V sense resistor ...
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... Boost Converter: Switch Duty Cycle and Frequency . SENSE The LT3758 can be confi gured as a boost converter for the applications where the converter output voltage is higher than the input voltage. Remember that boost con- verters are not short-circuit protected. Under a shorted output condition, the inductor current is limited only by the input supply capability ...
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... The power dissipated by the diode is: ), the gate to source O(MAX) ), the maximum GD and the diode junction temperature is LT3758 is higher than V VDSS 2 • R • • V L(MAX) DS(ON) MAX OUT is the reverse transfer capacitance, RSS and C DS(ON) RSS • ...
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... I = 0.3 • ΔI RMS(CIN) FLYBACK CONVERTER APPLICATIONS The LT3758 can be confi gured as a fl yback converter for the applications where the converters have multiple outputs, high output voltages or isolated outputs. Figure 7 shows a simplifi ed fl yback converter. The fl yback converter has a very low parts count for mul- ...
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... MOSFET or diode, and reduces effi ciency recommended to choose a duty cycle between 20% and 80 D2T , D3T . and Figure 8. Waveforms of the Flyback Converter in Discontinuous Mode Operation LT3758 , but higher SW(RMS) peak voltage DS D(RMS SW(MAX) ...
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... LT3758 APPLICATIONS INFORMATION Flyback Converter: Transformer Design for Discontinuous Mode Operation The transformer design for discontinuous mode of opera- tion is chosen as presented here. According to Figure 8, the minimum D3 (D3 ) occurs when the the converter MIN has the minimum V and the maximum output power ...
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... Boost Converter: Output Capacitor Selection section for the calculation The RMS ripple current rating of the output capacitors • I • DS(PEAK) L(MAX) in discontinuous operation can be determined using the following equation: I RMS COUT DISCONTINUOUS ( LT3758 • θ + θ • (θ FET JA A FET JC CA ...
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... V IN MIN ( SEPIC CONVERTER APPLICATIONS The LT3758 can be confi gured as a SEPIC (single-ended primary inductance converter), as shown in Figure 1. This topology allows for the input to be higher, equal, or lower than the desired output voltage. The conversion ratio as a function of duty cycle is: ...
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... The fi rst term in this equation represents the conduction losses in the device, and the second term, the switching loss the reverse transfer capacitance, which is RSS usually specifi the MOSFET characteristics. For maximum effi ciency, R minimized. From a known power dissipated in the power LT3758 2 χ • 1 ...
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... I RMS CDC ( A low ESR and ESL, X5R or X7R ceramic capacitor works well for C INVERTING CONVERTER APPLICATIONS The LT3758 can be confi gured as a dual-inductor invert- ing topology, as shown in Figure 10. The V 1 ratio is: D MAX V OUT ...
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... IC, and is important for thermal management of the IC. Therefore crucial to achieve a good electrical and thermal contact between the Exposed Pad and the ground plane of the board. For the LT3758 to deliver its full output power imperative that a good thermal path be pro- ⎞ ...
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... Place the divider resis- tors near the LT3758 in order to keep the high impedance FBX node short. Figure 11 shows the suggested layout of the 10V to 40V input, 48V output boost converter in the Typical Applica- tions section ...
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... Heat Sinks 972-243-4321 Capacitors 408-432-8020 Inductors 847-699-3430 Capacitors 847-696-2000 Resistors 605-665-9301 MOSFETs 800-554-5565 Inductors 605-886-4385 Capacitors 207-324-4140 Small-Signal Discretes 631-543-7100 LT3758 WEB ADDRESS avx.com bhelectronics.com coilcraft.com bussmann.com diodes.com fairchildsemi.com generalsemiconductor. com irf.com irctt.com kemet.com mag-inc.com microsemi.com murata.co.jp nichicon.com onsemi.com panasonic.com pulseeng ...
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... V = 24V 10V 0.001 0.1 0.01 OUTPUT CURRENT (A) 28 10V to 40V Input, 48V Output Boost Converter 200k IN SHDN/UVLO R4 32.4k LT3758 SYNC GATE SENSE RT SS FBX VC GND INTV VCC 0.68μF 4.7μF 10k 10V X5R 100pF 10nF ...
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... D1: ON SEMICONDUCTOR MBRS360T3G D : VISHAY SILICONIX ES1D MURATA GRM32ER61C476ME15L OUT 5V/DIV 10 3758 TA03b Frequency Foldback Waveforms When Output Short-Circuit V = 48V IN V OUT 5V/DIV V SW 50V/DIV 3758 TA03d 20μs/DIV LT3758 D1 V OUT 12V 1.2A T1 4,5,6 1,2,3 (PARALLEL) SW 105k OUT 15.8k 47μF 1% X5R 3758 TA03a Start-Up Waveform V ...
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... OUT2 D1: VISHAY SILICONIX ES1D Start-Up Waveforms V = 12V OUT1 V OUT2 20V/DIV 10ms/DIV SHDN/UVLO M1 SW LT3758 SYNC GATE SENSE RT SS FBX VC GND INTV CC C VCC 10k 0.019Ω 4.7μF 47pF 0.5W 10V 10nF X5R D2: VISHAY SILICONIX ES1C M1: VISHAY SILICONIX SI4848DY ...
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... VC BAS516 PS2801-1 2200pF 250VAC Effi ciency vs Output Current 100 36V V = 72V 48V 0.01 0.1 1 OUTPUT CURRENT (A) LT3758 C OUT 100μF 6.3V UPS840 x3 BAT54CWTIG 100k 47pF LT4430 47nF 0.47μF V OPTO IN 2k GND COMP OC 0.5V FB 1μF 10 3758 TA05b + V OUT 3.3V 3A ...
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... IN V OUT 10V/DIV 1A/DIV 2ms/DIV 32 18V to 72V Input, 24V Output SEPIC Converter • IN 232k V L1A IN SHDN/UVLO 20k LT3758 SYNC GATE M1 SENSE 0.025Ω FBX VC GND INTV CC 0.47μF 10k C VCC 4.7μF 10nF 10V X5R L1A, L1B: COILTRONICS DRQ127-470 ...
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... X5R L1A, L1B: COILTRONICS DRQ127-150 M1: VISHAY SILICONIX SI7850DP 500mV/DIV I OUT 1A/DIV 1 10 3757 TA07b V = 24V IN 10V/DIV 20V/DIV 5A/DIV 3757 TA07d LT3758 C DC 4.7μF 50V L1B V OUT -12V 2A D1 105k C 7.5k OUT 22μF 16V X5R x4 3757 TA07a Load Step Waveforms ...
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... LT3758 PACKAGE DESCRIPTION 3.50 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3 ...
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... MAX DETAIL “A” SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3758 2.06 0.102 (.081 .004) 0.29 REF 1.83 0.102 (.072 .004) 0.05 REF DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. DETAIL “B” FOR REFERENCE ONLY NO MEASUREMENT PURPOSE ...
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... LT3758 TYPICAL APPLICATIONS 8V to 72V Input, 12V Output SEPIC Converter 72V C IN 2.2μF 154k V IN 100V SHDN/UVLO X7R x2 32.4k LT3758 SYNC GATE SENSE RT SS FBX VC GND INTV 41.2k 300kHz 10k 0.47μF 10nF L1A, L1B: COILTRONICS DRQ127-220 RELATED PARTS PART NUMBER DESCRIPTION ...