LTC3879 Linear Technology Corporation, LTC3879 Datasheet
LTC3879
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LTC3879 Summary of contents
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... Safety features include output overvoltage protection and programmable current limit with foldback. The current limit is user programmable. The LTC3879 allows operation from 4V to 38V at the input and from 0.6V to 90% V available in a small 16-pin thermally enhanced MSOP or 3mm × 3mm QFN packages. ...
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... LTC3879EMSE#PBF LTC3879EMSE#TRPBF LTC3879IMSE#PBF LTC3879IMSE#TRPBF LTC3879EUD#PBF LTC3879EUD#TRPBF LTC3879IUD#PBF LTC3879IUD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. ...
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... TG High TG Low BG High BG Low C = 3300pF (Note 5) LOAD C = 3300pF (Note 5) LOAD C = 3300pF (Note 5) LOAD C = 3300pF (Note 5) LOAD C = 3300pF Each Driver (Note 5) LOAD C = 3300pF Each Driver (Note 5) LOAD LTC3879 MIN TYP MAX UNITS 1350 2000 μ μA l 0.594 0.6 0.606 V 0.005 %/V l –0.05 – ...
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... Note 3: The LTC3879 is tested in a feedback loop that adjusts V achieve a specifi ed error amplifi er output voltage (I 4 The l denotes the specifi cations which apply over the full operating = 25° 15V, unless otherwise noted CONDITIONS 6V < ...
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... Tracks External 1.8V Supply OUT V MASTER 0.5V/DIV V OUT 0.5V/DIV 3879 G07 5ms/DIV V = 12V 1.2V OUT SW FREQ = 400kHz FIGURE 10 CIRCUIT LTC3879 Transient Response FCM Negative Load Step V SW 20V/DIV V (AC) OUT 50mV/DIV I L 10A/DIV I LOAD 10A/DIV 3879 G02 5μs/DIV LOAD STEP 10A TO 0A ...
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... LTC3879 TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency vs Input Voltage 100 www.datasheet4u.com 95 15A CCM DCM CCM 15V 1.2V OUT SW FREQ = 400kHz 55 FIGURE 10 CIRCUIT (V) IN Current Sense Voltage vs I Voltage TH 300 250 200 150 100 ...
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... INPUT VOLTAGE (V) 3879 G18 INTV Dropout 12V –200 –400 –600 –800 –1000 –1200 INTV LOAD CURRENT (mA) CC 3879 G21 CC 50 100 3879 G24 LTC3879 Quiescent Current vs INTV 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 4.0 4.5 5.0 35 5.5 INTV CC 3879 G19 INTV vs INTV 4. ...
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... RUN (Pin 9): Run Control Input. RUN below 1.5V disables switching by forcing TG and BG low. RUN less than 1.5V but greater than 0.7V enables all internal bias including the INTV and places the LTC3879 into micropower shutdown mode of approximately 18μA. There is an internal 1.2μA pull-up current source for operation with an open-collector RUN signal. ...
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... MODE 0.8V – (10pF FCNT R DS( REV – RUN SWITCH LOGIC OV FCNT 0.6V 160μA 0.6V SOFT-START DONE 1.7ms SS + – – 1 LTC3879 0.6V REF 5.3V REF BOOST INTV VCC PGND 13 PGOOD 2 + 0.66V F – V ...
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... Increasing the load recover from foldback current limit, the excessive load or low impedance short needs to be removed. When RUN is less than 0.7V, the LTC3879 is in the low power shutdown state with a nominal bias current of 18μA. When RUN is greater than 0.7V and less than 1.5V, ...
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... APPLICATIONS INFORMATION The basic LTC3879 application circuit is shown on the fi rst page of this data sheet. External component selection is largely determined by maximum load current and begins www.datasheet4u.com with the selection of sense resistance and power MOSFET switches. The LTC3879 uses the on-resistance of the syn- chronous power MOSFET to determine the inductor current ...
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... Conversely, raising the operating frequency degrades effi ciency but reduces component size. The operating frequency of LTC3879 applications is de- termined implicitly by the one-shot timer that controls the on-time, t values ...
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... Minimum Off-Time and Dropout Operation The minimum off-time, t OFF(MIN) required for the LTC3879 to turn on the bottom MOSFET, trip the current comparator and then turn off the bottom MOSFET. This time is typically about 220ns. The minimum off-time limit imposes a maximum duty cycle of t ...
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... LTC3879 APPLICATIONS INFORMATION A reasonable starting point is to choose a ripple current that is about 40 The largest ripple current OUT(MAX) occurs at the highest guarantee that ripple current www.datasheet4u.com IN does not exceed a specifi ed maximum, the inductance should be chosen according to: ⎛ ⎞ ⎛ ...
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... Gate charge demands are greatest in high frequency low duty factor applications under high dI/dt load steps and at start-up. Setting Output Voltage The LTC3879 output voltage is set by an external feed- back resistive divider carefully placed across the output, as shown in Figure 5. The regulated output volt age is determined by: ⎛ ...
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... M and M T pulled to ground when RUN is less than 1.5V. When the RUN pin voltage is greater than 1.5V, the LTC3879 powers up. When not tracking, a soft-start current of 1μA is used to charge a soft-start capacitor placed on the TRACK/SS pin. Note that soft-start or tracking is achieved not by limiting the maximum output current of the control- ler, but instead by controlling the output voltage according to the ramp rate on the TRACK/SS pin ...
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... LTC3879’s output as a slave supply. To implement the coincident tracking in Figure 7, connect a resistor divider to the V , and connect its midpoint to the TRACK/SS MASTER pin of the LTC3879. The track divider should be the same as the LTC3879’s feedback divider. In this tracking mode, V must be higher than V OUT_MASTER ...
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... This can be better understood with the help of Figure 9. At the input stage of the LTC3879’s error amplifi er, two common anode diodes are used to clamp the equivalent reference voltage and an additional diode is used to match the shifted common mode voltage. The top two current sources are of the same amplifi ...
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... C V OUT OUT ΔI L Choose the synchronous bottom MOSFET switch and calculate the V V RNG LTC3879 or greater. This ripple voltage is equal P-P typical at 25°C • P-P = 4.5V to 28V (12V nominal 15A and f = 400kHz. Start OUT(MAX ...
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... A – • • ⎝ ⎜ • V RNG CMDSH-3 16 BOOST C B LTC3879 0.22μ PGND VCC 4.7μF 11 INV RUN Figure 10. Design Example: 1.2V/15A at 400kHz Verify that the calculated nominal T assumed worst-case ...
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... ESR and ESL in the output ripple and to improve load step response. PC Board Layout Checklist The LTC3879 PC board layout can be designed with or without a ground plane. A ground plane is generally pre- ferred based on performance and noise concerns. When using a ground plane, use a dedicated ground plane layer ...
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... PGND VCC SGND INTV RUN Figure 11. LTC3879 Layout Diagram Without Ground Plane D B CMDSH-3 16 BOOST C B LTC3879 0.22μ PGND VCC 4.7μF 11 INV RUN 0.1μ ...
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... BOOST C B LTC3879 0.22μ PGND VCC 4.7μF 11 INV RUN 0.1μF 2.2Ω LTC3879 V IN 4.5V TO 24V + C C IN2 IN1 56μF 10μF 25V 25V M1 L1 FDS8690 0.8μH V OUT 1.8V 10A + C OUT1 C M2 OUT2 330μF 100μF FDS8670 2 ...
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... SW 13 PGND VCC 4.7μF 11 INV RUN 0.1μF 2.2Ω 13V to 32V Input, 12V/5A Output at 300kHz D B ZLLS1000 16 BOOST C B LTC3879 0.22μ RNG 13 PGND VCC 4.7μF 11 INV RUN 0.1μF FB 2.2Ω 2. ...
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... CMDSH-3 16 BOOST C B LTC3879 0.22μ PGND VCC 4.7μF 11 INV RUN 0.1μF 2.2Ω LTC3879 V IN 4.5V TO 20V + C C IN1 IN2 V I 82μF 10μF IN OUT 25V 25V 5V 4A 12V 7A M1 20V 8A L1 RJK0304DPB 2.2μ OUT1 OUT2 M2 120μ ...
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... LTC3879 PACKAGE DESCRIPTION www.datasheet4u.com 2.845 0.102 (.112 .004) 5.23 (.206) MIN 0.305 0.038 (.0120 .0015) TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) GAUGE PLANE 0.18 (.007) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006" ...
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... LTC DWG # 05-08-1700 Rev A) Exposed Pad Variation AA 0.70 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 0.75 0.05 3.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) 1.65 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LTC3879 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP R = 0.115 OR 0.25 45 CHAMFER TYP 15 16 0.40 0. (UD16 VAR A) QFN 1207 REV A 0.25 0.05 0.50 BSC 3879f 27 ...
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... LTC3879 RELATED PARTS PART NUMBER DESCRIPTION LTC3608/LTC3609 8A/6A Monolithic Synchronous Step-Down DC/DC Converters Optimized for High Step-Down Ratios, V LTC3610/LTC3611 12A/10A Monolithic Synchronous Step-Down DC/DC www.datasheet4u.com Converters LTC3728 2-Phase 550kHz, Dual Synchronous Step-Down Controller LTC3770 No R Synchronous Step-Down Controller with Voltage SENSE Margining, PLL and Tracking ...