LTC3856EFE#PBF Linear Technology, LTC3856EFE#PBF Datasheet

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... A TK/SS pin shared by both chan- nels ramps the output voltage during start-up. L, LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase, Burst Mode and OPTI-LOOP are registered trademarks and Stage Shedding is a trademark 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, 6498466, 6580258, 6611131, 6674274 ...

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LTC3856 absoluTe MaxiMuM raTings Input Supply Voltage (V ) ......................... 40V to –0.3V IN Topside Driver Voltages (BOOSTn) ............ 46V to –0.3V Switch Voltage (SWn) ................................... 40V to –5V INTV , RUN, PGOOD, EXTV , CC CC (BOOSTn – SWn) ...

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... LEAD FREE FINISH TAPE AND REEL LTC3856EFE#PBF LTC3856EFE#TRPBF LTC3856IFE#PBF LTC3856IFE#TRPBF LTC3856EUH#PBF LTC3856EUH#TRPBF LTC3856IUH#PBF LTC3856IUH#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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LTC3856 elecTrical characTerisTics junction temperature range, otherwise specifications are at T SYMBOL PARAMETER TG Transition Time TG1,2 t Rise Time r TG1,2 t Fall Time f BG Transition Time BG1,2 t Rise Time r BG1,2 t Fall Time f TG/BG ...

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T SYMBOL PARAMETER Differential Amplifier A Gain DA R Input Resistance IN V Input Offset Voltage OS PSRR Power Supply Rejection Ratio I Maximum Output Current CL V Maximum Output Voltage ...

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LTC3856 Typical perForMance characTerisTics Load Step: Burst Mode Operation V = 3.6V BAT 200µA LOAD CPO 40A/DIV C = 2.2 F CPO I L1 20A/DIV I L2 20A/DIV V OUT 200mV/DIV 100µs/DIV V = 12V IN V ...

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Typical perForMance characTerisTics Load Step without AVP 108mV V OUT 50mV/DIV 50A I L 25A 20A/DIV 3856 G07 100µs/DIV V = 12V 1.5V OUT INTV Line Regulation CC 5.25 5.00 4.75 4.50 4.25 4.00 3.75 3.50 3.25 ...

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LTC3856 Typical perForMance characTerisTics Shutdown (RUN) Threshold vs Temperature 1.25 ON 1.20 1.15 OFF 1.10 –50 – 100 125 TEMPERATURE (°C) 3856 G15 Undervoltage Lockout Threshold (INTV ) vs Temperature CC 4.0 ON 3.8 3.6 3.4 ...

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FuncTions (TSSOP/QFN) FREQ (Pin 1/Pin 29): Frequency Setting Pin. A resistor to ground sets the operating frequency of the controller. This pin can also be driven with a DC voltage to vary the frequency of the internal oscillator. RUN ...

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LTC3856 pin FuncTions (TSSOP/QFN) INTV (Pin 29/Pin 21): Internal 5V Regulator Output. The CC control circuits are powered from this voltage. Decouple this pin to PGND with a minimum of 4.7µF low ESR tan- talum or ceramic capacitor. V (Pin ...

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FuncTional DiagraM MODE PLLIN PHASMD FREQ MODE/SYNC DETECT PLL-SYNC CLKOUT OSC – CMP REV – + ISET ISET ISET I LIM SLOPE COMPENSATION INTV UVLO CC 1 51k SLOPE RECOVERY I THB ACTIVE ...

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LTC3856 operaTion (Refer to Functional Diagram) Main Control Loop The LTC3856 uses a constant-frequency, current mode step-down architecture. During normal operation, each top MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when ...

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Functional Diagram) Light Load Current Operation (Burst Mode Operation, Stage Shedding or Continuous Conduction) The LTC3856 can be enabled to enter high efficiency Burst Mode operation, Stage Shedding mode or forced continuous conduction mode. To select forced ...

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LTC3856 operaTion (Refer to Functional Diagram) operating frequency from 250kHz to 770kHz. There is a precision 10µA current flowing out of the FREQ pin enabling the user to program the controller’s switching frequency with a single resistor to SGND. A ...

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The Typical Application on the first page of this data sheet is a basic LTC3856 application circuit. LTC3856 can be configured to use either DCR (inductor resistance) sens- ing or low value resistor sensing. The choice between the ...

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LTC3856 applicaTions inForMaTion Low Value Resistors Current Sensing A typical sensing circuit using a discrete resistor is shown in Figure 2a chosen based on the required SENSE output current. The current comparator has a maximum threshold ...

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In the absence of data, measure the voltage drop directly across the sense resistor to extract the magnitude of the ESL step and use Equation 1 to determine the ESL. However, do ...

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LTC3856 applicaTions inForMaTion The LTC3856 also features a DCR temperature compensa- tion circuit by using a NTC temperature sensor. See the Inductor DCR Sensing Temperature Compensation and the ITEMP Pin section for details. The maximum power loss ...

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NTC Compensated DCR Sensing For DCR sensing applications where a more accurate current limit is required, a network consisting of an NTC thermistor placed from the ITEMP pin to ground will provide correction of the current limit over ...

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LTC3856 applicaTions inForMaTion After determining the components for the temperature compensation network, check the results by plotting I versus inductor temperature using the following MAX equations MAX ∆ − V SENSEMAX ADJ ( )  DCR AT 25 ...

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Inductor Value Calculation and Output Ripple Current The operating frequency and inductor selection are inter- related in that higher operating frequencies allow the use of smaller inductor and capacitor values. A higher frequency generally results in lower efficiency ...

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LTC3856 applicaTions inForMaTion The peak-to-peak MOSFET gate drive levels are set by the voltage requiring the use of logic-level threshold CC MOSFETs in most applications. Pay close attention to the BV specification for the MOSFETs as well; many ...

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The term (1 + δ generally given for a MOSFET in the form of a normalized R vs temperature curve, but DS(ON) δ = 0.005/°C can be used as an approximation for low voltage MOSFETs. The ...

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LTC3856 applicaTions inForMaTion reduced by the reduction of the input ripple current in a PolyPhase system. The required amount of input capaci- tance is further reduced by the factor N, due to the effective increase in the frequency of the ...

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The amplifier has an output swing range 3.6V. The output uses an NPN emitter follower with 80k feedback resistance. Active Voltage Positioning (AVP application, the AVP scheme modifies the regulated output ...

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LTC3856 applicaTions inForMaTion Soft-Start and Tracking The LTC3856 has the ability to either soft-start by itself with a capacitor or track the output of another external supply. When the controller is configured to soft-start by itself, a capacitor should be ...

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TIME (11a) Coincident Tracking Figure 11. Two Different Modes of Output Voltage Tracking V OUT1 TK/SS2 V PIN PIN R4 R2 (12a) Coincident Tracking Set-Up Figure 12. Set-Up and Coincident and Ratiometric Tracking is ...

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LTC3856 applicaTions inForMaTion short circuit). If more current is required through the EXTV than is specified, an external Schottky diode can CC be added between the EXTV and INTV CC apply more than 6V to the EXTV pin and make ...

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Setting Output Voltage If the DIFFAMP is not used, the LTC3856 output voltage is set by an external feedback resistive divider carefully placed across the output, as shown in Figure 14. The regulated output voltage is determined by: ...

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LTC3856 applicaTions inForMaTion Phase-Locked Loop and Frequency Synchronization The LTC3856 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 ...

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OSC the filter network. If the external and internal frequencies are the same but exhibit a phase difference, the current sources turn on for an amount of time ...

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LTC3856 applicaTions inForMaTion the topside MOSFET and the synchronous MOSFET. If the two MOSFETs have approximately the same R then the resistance of one MOSFET can simply be summed with the resistances of L and R 2 tain I R ...

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A second, more severe transient is caused by switching in loads with large (>1µF) supply bypass capacitors. The discharged bypass capacitors are effectively put in parallel with C , causing a rapid drop in V OUT alter its ...

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LTC3856 applicaTions inForMaTion A short-circuit to ground will result in a folded back current of  −  SC Ω µ 0 002 .  ...

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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 17. Check ...

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LTC3856 applicaTions inForMaTion BOLD LINES INDICATE HIGH, SWITCHING CURRENT LINES. KEEP LINES TO A MINIMUM LENGTH. Figure 17. Instantaneous Current Path Flow in a Multiple Phase Switching Regulation  SW1 L1 R SENSE1 ...

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Typical applicaTion 1nF V IN 0.1µF 2.2 S 5.6k 100pF S S SENSE1 CLKOUT V IN PLLIN SENSE1 100k, 1% FREQ RUN 0.1µF TK/SS I BOOST1 TH 20k LTC3856 INTV AVP ITEMP PHASMD 30.1k DIFFP BOOST2 DIFFN ...

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LTC3856 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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... EXPOSED PAD SHALL BE SOLDER PLATED 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. UH Package 32-Lead Plastic QFN (5mm × ...

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... IN ON(MIN) ≤ 38V, 0.8V ≤ V ≤ 12V IN OUT ≤ 24V 13.5V IN OUT3 ≤ 30V, 0.8V ≤ V ≤ 5.25V IN OUT LT 0510 • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2010 V IN 4.5V TO 14V GND V OUT 1.5V/ 50A 4.7µF 6.3V 3856f ...