LTC3855IFE#TRPBF Linear Technology, LTC3855IFE#TRPBF Datasheet
LTC3855IFE#TRPBF
Specifications of LTC3855IFE#TRPBF
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LTC3855IFE#TRPBF Summary of contents
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... QFN and 38-lead exposed pad FE packages. L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and PolyPhase are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. 22µ ...
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LTC3855 absoluTe MaxiMuM raTings (Note 1) Input Supply Voltage (V ) ......................... –0.3V to 40V IN Top Side Driver Voltages BOOST1, BOOST2 .................................. –0.3V to 46V Switch Voltage (SW1, SW2) ......................... –5V to 40V INTV , RUN1, RUN2, PGOOD(s), EXTV ...
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... LEAD FREE FINISH TAPE AND REEL LTC3855EFE#PBF LTC3855EFE#TRPBF LTC3855IFE#PBF LTC3855IFE#TRPBF LTC3855EUJ#PBF LTC3855EUJ#TRPBF LTC3855IUJ#PBF LTC3855IUJ#TRPBF Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. ...
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LTC3855 elecTrical characTerisTics junction temperature range (E-Grade), otherwise specifications are at T SYMBOL PARAMETER TG/BG t Top Gate Off to Bottom Gate On Delay 1D Synchronous Switch-On Delay Time BG/TG t Bottom Gate Off to Top Gate On Delay 2D ...
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T SYMBOL PARAMETER On Chip Driver Pull- DS(ON Pull-Down R DOWN DS(ON Pull- DS(ON ...
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LTC3855 Typical perForMance characTerisTics Load Step (Burst Mode Operation) I LOAD 5A/DIV 300mA 5A/DIV V OUT 100mV/DIV AC-COUPLED 50µs/DIV V = 12V 1.8V OUT Load Step (Pulse-Skipping Mode) I LOAD 5A/DIV 300mA TO ...
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Typical perForMance characTerisTics Tracking Up and Down with External Ramp TK/SS1 TK/SS2 2V/DIV V OUT1 V OUT2 V OUT1 V OUT2 500mA/DIV 3855 10ms/DIV V = 12V 1.8V, 1.5 LOAD OUT1 V = 1.2V, 1 LOAD OUT2 ...
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LTC3855 Typical perForMance characTerisTics Shutdown (RUN) Threshold vs Temperature 1.26 1.24 1.22 ON 1.20 1.18 1.16 1.14 OFF 1.12 1.10 – 100 –25 0 TEMPERATURE (°C) 3855 G15 Undervoltage Lockout Threshold (INTV ) vs Temperature CC 4.1 ...
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FuncTions (FE38/UJ40) ITEMP1, ITEMP2 (Pin 2, Pin 1/Pin 37, Pin 36): Inputs of the temperature sensing comparators. Connect each of these pins to external NTC resistors placed near induc- tors. Floating these pins disables the DCR temperature compensation function. ...
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LTC3855 pin FuncTions (FE38/UJ40) BOOST1, BOOST2 (Pin 32, Pin 24/Pin 29, Pin 21): Boosted Floating Driver Supplies. The (+) terminal of the bootstrap capacitors connect to these pins. These pins swing from a diode voltage drop below INTV up to ...
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FuncTional block DiagraM FREQ MODE/PLLIN PHASMD TEMPSNS MODE/SYNC DETECT PLL-SYNC CLKOUT OSC – I CMP + – SLOPE COMPENSATION I LIM INTV CC 1 SLOPE RECOVERY 51k ACTIVE CLAMP I THB SLEEP V IN 0.6V REF ...
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LTC3855 operaTion Main Control Loop The LTC3855 is a constant-frequency, current mode step- down controller with two channels operating 180 degrees out-of-phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS ...
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SGND). To select pulse-skipping mode of operation, tie the MODE/PLLIN pin to INTV select Burst Mode operation, float the MODE/PLLIN pin. When a controller is enabled for Burst Mode operation, the peak current in the ...
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LTC3855 operaTion Sensing the Output Voltage with a Differential Amplifier The LTC3855 includes a low offset, unity gain, high band- width differential amplifier for applications that require true remote sensing. Sensing the load across the load capaci- tors directly greatly ...
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LTC3855’s controllers can be selected using the FREQ pin. If the MODE/PLLIN pin is not being driven by an external clock source, the FREQ pin can be used to program the controller’s operating frequency from 250kHz ...
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LTC3855 applicaTions inForMaTion less than 1µA. When the SENSE pins ramp up from 0V to 1.4V, the small base currents flow out of the SENSE pins. When the SENSE pins ramp down from 12.5V to 1.1V, the small base currents ...
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V IN INTV CC BOOST TG SW LTC3855 BG PGND SENSE C F – SENSE SGND R F 3855 F02a FILTER COMPONENTS PLACED NEAR SENSE PINS (2a) Using a Resistor to Sense Current the resulting ...
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LTC3855 applicaTions inForMaTion always the same and varies with temperature; consult the manufacturers’ datasheets for detailed information. Using the inductor ripple current value from the Inductor Value Calculation section, the target sense resistor value is: V SENSE(MAX SENSE(EQUIV) ...
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V ITEMP 100 ITEMP 100 C 10 µA = − • ITEMP 100 C I • DCR MAX • ° ...
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LTC3855 applicaTions inForMaTion 10000 THERMISTOR RESISTANCE R = 100k 25° 1000 B = 4334 for 25°C/100°C 100 RITMP R = 20k 43. 100k NTC 1 –40 – ...
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A reasonable starting point is to choose a ripple current that is about 40 for a duty cycle less than OUT(MAX) 40%. Note that the largest ripple current occurs at the highest input voltage. To guarantee ...
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LTC3855 applicaTions inForMaTion The MOSFET power dissipations at maximum output current are given by OUT = MAIN MAX ...
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To minimize this error, select the tracking resistive divider value to be small enough to make this error negligible. In order to track down another channel or supply after the soft-start phase expires, ...
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LTC3855 applicaTions inForMaTion INTV Regulators and EXTV CC CC The LTC3855 features a true PMOS LDO that supplies power to INTV from the V supply. INTV CC IN gate drivers and much of the LTC3855’s internal circuitry. The linear regulator ...
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Make sure the INTV exceeds the R test voltage for the MOSFET DS(ON) which is typically 4.5V for logic level devices LTC3855 INTV CC CINTV CC 4.7µF Figure ...
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LTC3855 applicaTions inForMaTion can also be used for C . Always consult the manufacturer IN if there is any question. The benefit of the LTC3855 2-phase operation can be cal- culated by using the equation above for the higher power ...
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Phase-Locked Loop and Frequency Synchronization The LTC3855 has a phase-locked loop (PLL) comprised of an internal voltage-controlled oscillator (V detector. This allows the turn-on of the top MOSFET of controller locked to the rising edge ...
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LTC3855 applicaTions inForMaTion If the duty cycle falls below what can be accommodated by the minimum on-time, the controller will begin to skip cycles. The output voltage will continue to be regulated, but the ripple voltage and current will increase. ...
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C adequate charge storage and very low ESR at the switch- ing frequency. A 25W supply will typically require a minimum of 20µF to 40µF of capacitance having a maximum ...
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LTC3855 applicaTions inForMaTion PC Board Layout Checklist When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the IC. These items are also illustrated graphically in the layout diagram of Figure 14. ...
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IN Figure 14. Recommended Printed Circuit Layout Diagram BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. TK/SS1 R PU2 CLKOUT V PULL-UP I PGOOD PGOOD TH1 DIFFP ...
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LTC3855 applicaTions inForMaTion This occurs around 50% duty cycle on either channel due to the phasing of the internal clocks and may cause minor duty cycle jitter. Reduce V from its nominal level to verify operation IN of the regulator ...
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M1 0.1µF L1 0.56µH M2 3.09k 1% 40. OUT1 1.8V 15A 1nF + C OUT1 20k 12.1k 330µ L1, L2: VISHAY IHLP4040DZ-01, 0.56µH M1, M3: RENESAS RJK0305DPB M2, M4: RENESAS RJK0330DPB Figure ...
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LTC3855 applicaTions inForMaTion MOSFET results in 13mΩ (max), V DS(ON) ≅ 150pF . At maximum input voltage with T 2.6V, C MILLER (estimated) = 75°C: 1. 15A 1+ (0.005)(75°C – 25°C) MAIN ...
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Typical applicaTions 100 1nF 40.2k 0.1µF 1nF 18k TK/SS1 I TH1 20k 150pF V FB1 SGND 150pF V FB2 20k I TH2 TK/SS2 + 5.49k SENSE2 1.5nF 1nF – SENSE2 DIFFP 0.1µF 100 100 20k L1, L2: VITEC 59PR9875 C ...
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LTC3855 Typical applicaTions 100 1nF TK/SS1 0.1µF I TH1 V FB1 SGND V FB2 20k I TH2 TK/SS2 2200pF + SENSE2 100pF 1nF – SENSE2 20k 5.9k DIFFP 100 100 L1, L2: PULSE PA0513.441NLT C : MURATA GRM31CR60J107ME39L OUT1 C ...
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Typical applicaTions 0.1µF TK/SS1 0.1µF I TH1 V FB1 SGND V FB2 20k I TH2 TK/SS2 3300pF + SENSE2 330pF 0.1µF – SENSE2 20k 10k DIFFP L1, L2: VISHAY IHLP5050FD-01, 0.47µ MURATA GRM31CR60J107ME39L OUT1 C : SANYO 2R5TPE330M9 ...
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LTC3855 Typical applicaTions 100 1nF TK/SS1 0.1µF I TH1 V FB1 SGND V FB2 10k I TH2 TK/SS2 2700pF + SENSE2 220pF 1nF – SENSE2 20k 5.1k DIFFP 100 100 L1, L2: VITEC 59PR9873 C : MURATA GRM31CR60J107ME39L OUT1 C ...
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Typical applicaTions 100 0.1µF 13.3k 4700pF 330pF 1nF 20k 2k 100 100 100 90.9k 3300pF 20k 0.1µF 10k 0.1µF 100pF L1, L2, L3: VITEC 59PR9874 L4: WURTH 744311220 TDK C3225X5R0J107M OUT1 OUT3 C : KEMET T530D477M2R5ATE006 ...
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LTC3855 Typical applicaTions 4.7µF Si4816BDY M1 L2 2.2µH 8mΩ 15pF V OUT1 3.3V 5A 90.9k 1% 1000pF + 20k C 10k OUT1 1% 1% 220µF L1: TDK RLF 7030T-2R2M5R4 L2: TDK ULF10045T-3R3N6R9 C : SANYO 4TPE220MF OUT1 C : SANYO ...
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Typical applicaTions 0.1µF 383k 0.1µF 5.6nF 10k TK/SS1 I TH1 20k 47pF V FB1 SGND 47pF V FB2 20k I TH2 TK/SS2 + SENSE2 4.99k 5.6nF 0.1µF – SENSE2 DIFFP 0.1µF 147k L1: WURTH 7443551131 L2: WURTH 7443551370 C , ...
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LTC3855 package DescripTion 4.75 REF 6.60 ±0.10 4.50 REF SEE NOTE 4 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 0.50 – 0.75 (.0035 – .0079) (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. ...
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... SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...
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... LTC3868-1 DC/DC Controller with 99% Duty Cycle LT3845 Low I , High Voltage Synchronous Step-Down DC/DC Q Controller trademark of Linear Technology Corporation. µModule is a registered trademark of Linear Technology Corporation. SENSE Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● COMMENTS Phase-Lockable Fixed 250kHz to 750kHz Frequency, 4V ≤ ...