LTC3731 Linear Technology, LTC3731 Datasheet
LTC3731
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LTC3731 Summary of contents
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... PolyPhase synchronous step-down , LTC and LT are registered trademarks of Linear Technology Corporation 28V + 0.8µH 0.003Ω 22µF 35V V IN 0.8µH V 0.003Ω OUT 1.35V 55A V IN 0.8µH 0.003Ω OUT 470µF 4V 3731 F01 LTC3731 3731fa 1 ...
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... V Regulated Voltage at IN REGULATED (Note 1) ) ............ 38V to –0. Operating Ambient Temperature Range LTC3731C .................................................... 0°C to 70°C – .... 7V to –0. LTC3731I ................................................. –40°C to 85° ..................... PGOOD Junction Temperature (Note 2) ............................. 125°C Storage Temperature Range ..................–65°C to 150°C Lead Temperature G Package (Soldering, 10sec).. 300° ...
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... Voltage = 1. LTC3731IG 1.2V, Sink/Source 25µA (Note LTC3731IG I = 1.2V (g • Series 1k-100kΩ-1nF LTC3731IG V = 0.65V FCB Measured at FCB Pin V Lowered Until the RUN/SS Pin is Pulled Low CC At UVADJ Threshold (Note RUN/ 1.9V RUN/SS V ...
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... D LTC3731CG/LTC3731IG LTC3731CG/LTC3731IG LTC3731CUH/LTC3731IUH Note 3: The IC is tested in a feedback loop that includes the differential amplifier loaded with 100µA to ground driving the error amplifier and servoing the resultant voltage to the midrange point for the error amplifier (V = 1.2V). ITH ...
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... RUN/SS capacitor controller circuit power as well as the high power pulses supplied to drive the external MOSFET gates in the LTC3731CUH, this pin needs to be very carefully and closely decoupled to the IC’s PGND pin. VDR: (LTC3731G Package Only) Supplies power to the bottom gate drivers only. This pin needs to be very carefully and closely decoupled to the IC’ ...
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... LTC3731 TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs I (Figure 14) OUT 100 V = OPEN 90 FCB FCB FCB www.DataSheet4U.com 0 INDUCTOR CURRENT (A) Reference Voltage vs Temperature 610 605 600 595 590 –50 – TEMPERATURE (°C) Oscillator Frequency vs Temperature 700 ...
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... G14 I Pin Current vs V SENSE PLLFLTR –10 –20 – 100 125 3731 G17 LTC3731 50 75 100 125 3731 G12 ITH 1.2 1.8 2.4 V (V) ITH 3731 G15 OUT (V) OUT 3731 G18 3731fa 7 ...
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... LTC3731 TYPICAL PERFOR A CE CHARACTERISTICS www.DataSheet4U.com Shed Mode at 1 Amp, Light Load Current (Circuit of Figure 14) V OUT AC, 20mV/DIV V SW1 10V/DIV V SW2 10V/DIV V SW3 10V/DIV V = 12V 4µs/DIV 1.5V OUT FCB CC FREQUENCY = 250kHz Continuous Mode at 1 Amp, Light Load Current (Circuit of Figure 14) ...
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... UVADJ – 1.2V + *THE LTC3731CUH USES THE EXPOSED DIE ATTACH PAD FOR THE SGND CONNECTIONS **THE PHASMD AND PGOOD PIN FUNCTIONS ARE TIED TOGETHER IN THE LTC3731CUH PACKAGE ***LTC3731CG/HG ONLY W CLK1 CLK2 CLK3 DUPLICATE FOR SECOND AND THIRD – 0.66V CONTROLLER CHANNELS ...
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... LTC3731 U OPERATIO (Refer to Functional Diagram) Main Control Loop The IC 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 the main current comparator resets each RS latch. The peak inductor ...
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... If the condition lasts for a long enough period, as determined by the size of the RUN/SS capacitor, the controller will be shut down until the RUN/SS pin voltage is recycled. This built-in latchoff LTC3731 will result 3731fa 11 ...
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... LTC3731 U OPERATIO (Refer to Functional Diagram) can be overridden by providing >5µ compliance of 3.8V to the RUN/SS pin. This additional current shortens the soft-start period but prevents net discharge of the RUN/SS capacitor during a severe overcurrent and/or short-circuit condition. Foldback current limiting is acti- vated when the output voltage falls below 70% of its nominal level whether or not the short-circuit latchoff circuit is enabled ...
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... Kool Mµ. Toroids are very space efficient, especially when you can use several layers of wire. Be- cause they lack a bobbin, mounting is more difficult. However, designs for surface mount are available which do not increase the height significantly. Kool Mµ registered trademark of Magnetics, Inc. LTC3731 1.0 1-PHASE 0.9 2-PHASE 3-PHASE ...
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... LTC3731 U U APPLICATIO S I FOR ATIO Power MOSFET and D1, D2, D3 Selection At least two external power MOSFETs must be selected for each of the three output sections: One N-channel MOSFET for the top (main) switch and one or more N-channel MOSFET(s) for the bottom (synchronous) switch. The number, type and “ ...
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... OUT where ..., – – 1 OUT where ..., 0.6 0.5 1-PHASE 2-PHASE 0.4 3-PHASE 4-PHASE 6-PHASE 0.3 12-PHASE 0.2 0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 DUTY FACTOR ( OUT IN 3731 F06 Figure 6. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Output Stages LTC3731 0.9 3731fa 15 ...
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... LTC3731 U U APPLICATIO S I FOR ATIO size or height requirements in the design. Always consult the capacitor manufacturer if there is any question. The Figure 6 graph shows that the peak RMS input current is reduced linearly, inversely proportional to the number N of stages used important to note that the efficiency ...
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... CC of the controller but also to the top and bottom gate drivers on the LTC3731CUH and therefore must be by- passed very carefully to ground with a ceramic capacitor, type X7R or X5R (depending upon the operating tempera- ture environment least 1 µ F imme diately next to the IC and preferably an additional 10µ ...
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... LTC3731 U U APPLICATIO S I FOR ATIO Soft-Start/Run Function The RUN/SS pin provides three functions: 1) ON/OFF, 2) soft-start and 3) a defeatable short-circuit latch off timer. Soft-start reduces the input power sources’ surge currents by gradually increasing the controller’s current limit (pro- portional to an internal buffered and clamped V latchoff timer prevents very short, extreme load transients from tripping the overcurrent latch ...
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... Thus, the voltage on the rises above 4V, the RUN/SS capaci voltage applied ∆f = ±0.5 f ∆ greater than the oscil- PLLIN , current is sourced continuously, OSC , current is sunk continuously, pulling OSC LTC3731 ) 3731fa 19 ...
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... LTC3731 U U APPLICATIO S I FOR ATIO PHASE DETECTOR/ OSCILLATOR EXTERNAL OSC OSC PLLIN DIGITAL PHASE/ FREQUENCY DETECTOR 50k www.DataSheet4U.com Figure 9. Phase-Locked Loop Block Diagram PLLFLTR pin is adjusted until the phase and frequency of the external and internal oscillators are identical. At this stable operating point, the phase comparator output is ...
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... Note that the transient suppressor should not conduct during double-battery operation, but must still clamp the input voltage below breakdown of the LTC3731 , causing a rapid drop regulator can OUT OUT ...
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... LTC3731 U U APPLICATIO S I FOR ATIO LTC3731 www.DataSheet4U.com Figure 10. Automotive Application Protection converter. Although the IC has a maximum input voltage of 32V on the SW pins, most applications will be limited to 30V by the MOSFET BV DSS Design Example As a design example, assume 20V(max 1.3V OUT The inductance value is chosen first based upon a 30% ripple current assumption ...
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... IC. These items are also illustrated graphically in the layout diagram of Figure 11. Check the following in the PC layout: L1 SW1 R SENSE1 D1 L2 SW2 R SENSE2 D2 L3 SW3 R SENSE3 D3 Figure 11. Branch Current Waveforms LTC3731 V OUT + OUT 3731 F11 3731fa 23 ...
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... IC power ground pin (PGND). connect to the drains of the This technique keeps inherent signals generated by high current pulses taking alternate current paths that have fi- nite impedances during the total period of the switching INDUCTOR LTC3731 + SENSE 1000pF – SENSE OUTPUT CAPACITOR Figure 12 ...
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... MOSFET on. The SINGLE PHASE CIN I COUT TRIPLE PHASE V SW1 V SW2 V SW3 CIN I COUT 3731 F13 Figure 13. Single and Polyphase Current Waveforms LTC3731 /L discharge currents OUT – V )/L charging current CC OUT 3731fa 25 ...
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... LTC3731 U U APPLICATIO S I FOR ATIO output ripple current for a 3-phase design is: V OUT ( ) – The ripple frequency is also increased by three, further reducing the required output capacitance when V as illustrated in Figure 6. The addition of more phases by phase locking additional www.DataSheet4U.com ...
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... Main switch’s AC loss (V = 12V) 2.25W 3.75% IN Main switch’s DC loss Synchronous switch AC loss Synchronous switch DC loss Power path loss to better balance the AC MILLER LTC3731 0.87W 1.5% 0.19W 0.3% 7.2W 12% 3.7W 6.1% = 12V 3731fa 27 ...
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... Figure 14. 3-Phase 65A Power Supply V 1µF CC 10Ω CLK PLLIN PGOOD 3 34 PLLFLTR BOOST1 0.1µ FCB TG1 SW1 LTC3731 6 31 – IN BOOST2 0.1µ DIFFOUT TG2 8 29 EAIN SW2 9 28 SGND SENSE1 BG1 1µF 10µ – ...
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... X2 D6 M17,18 + – L6: TOKO FDH1040: 0.56µ 10µF/16V CERAMIC × 270µF/16V SANYO Os-Con 100µF/6.3V/X5R × 330µF/4V × 8 OUT LTC3731 V5 + 10µF 10V V OUT + C OUT 3731 F15 3731fa ...
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... LTC3731 PACKAGE DESCRIPTIO 7.8 – 8.2 www.DataSheet4U.com 0.42 ±0.03 RECOMMENDED SOLDER PAD LAYOUT 5.00 – 5.60** (.197 – .221) 0.09 – 0.25 (.0035 – .010) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE * DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE ** DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH ...
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... 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC3731 BOTTOM VIEW—EXPOSED PAD R = 0.115 ...
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... LTC3731 RELATED PARTS PART NUMBER DESCRIPTION LTC1628/LTC3728 2-Phase, Dual Output Synchronous Step-Down DC/DC Controllers LTC1629/LTC3729 20A to 200A PolyPhase Synchronous Controllers LTC1702 No R SENSE Controller LTC1703 No R SENSE Controller with 5-Bit Mobile VID Control LTC1708-PG 2-Phase, Dual Synchronous Controller with Mobile VID www.DataSheet4U.com ® ...