ltc3787gn Linear Technology Corporation, ltc3787gn Datasheet
ltc3787gn
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ltc3787gn Summary of contents
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FeaTures 2-Phase Operation Reduces Required Input and n Output Capacitance and Power Supply Induced Noise Synchronous Operation for Highest Efficiency and n Reduced Heat Dissipation Wide V Range: 4.5V to 38V (40V Abs Max) and n IN Operates Down to ...
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... EXPOSED PAD (PIN 29) IS GND, MUST BE CONNECTED TO GND PART MARKING* PACKAGE DESCRIPTION 3787 28-Lead (4mm × 5mm) Plastic QFN 3787 28-Lead (4mm × 5mm) Plastic QFN LTC3787GN 28-Lead Plastic SSOP LTC3787GN 28-Lead Plastic SSOP http://www.linear.com/leadfree/ http://www.linear.com/tapeandreel/ – + – , SENSE2 , SENSE2 ... – ...
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T SYMBOL PARAMETER Main Control Loop VBIAS Chip Bias Voltage Operating Range V Regulated Feedback Voltage FB I Feedback Current FB V Reference Line Voltage Regulation REFLNREG V Output Voltage Load ...
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LTC3787 elecTrical characTerisTics junction temperature range, otherwise specifications are at T SYMBOL PARAMETER DF Maximum BG Duty Factor BG1,2(MAX) t Minimum BG On-Time ON(MIN) INTV Linear Regulator CC V Internal V Voltage INTVCC(VIN) CC VLDO INT INTV Load Regulation CC ...
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Typical perForMance characTerisTics Efficiency and Power Loss vs Output Current 100 0.01 0.1 OUTPUT CURRENT (A) BURST EFFICIENCY PULSE-SKIPPING EFFICIENCY FORCED CONTINUOUS MODE EFFICIENCY Efficiency vs Load Current 100 V ...
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LTC3787 Typical perForMance characTerisTics Inductor Current at Light Load FORCED CONTINUOUS MODE Burst Mode OPERATION 5A/DIV PULSE-SKIPPING MODE V = 12V 5µs/DIV 24V OUT I = 200µA LOAD FIGURE 10 CIRCUIT Regulated Feedback Voltage vs Temperature 1.212 ...
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Typical perForMance characTerisTics Quiescent Current vs Temperature 180 V = 12V 1.25V FB 170 RUN = GND 160 150 140 130 120 110 –45 – TEMPERATURE (°C) Undervoltage Lockout Threshold vs Temperature 4.4 4.3 INTV ...
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LTC3787 Typical perForMance characTerisTics Oscillator Frequency vs Temperature 600 FREQ = INTV 550 500 450 400 FREQ = GND 350 300 –45 – TEMPERATURE (°C) Maximum Current Sense Threshold vs I Voltage TH 120 100 PULSE-SKIPPING MODE 80 ...
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Typical perForMance characTerisTics Maximum Current Sense Threshold vs Duty Cycle 120 I = INTV LIM CC 100 I = FLOAT 80 LIM GND LIM ...
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LTC3787 pin FuncTions (QFN/SSOP) SS (Pin 7/Pin 10): Output Soft-Start Input. A capacitor to ground at this pin sets the ramp rate of the output voltage during start-up. – – SENSE2 , SENSE1 (Pin 8, Pin 28/Pin 11, Pin 3): ...
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DiagraM PHASMD CLKOUT 20µA FREQ CLK2 VCO CLK1 PFD PLLIN/ MODE SYNC DET 100k ILIM CURRENT LIMIT VBIAS SHDN EXTV CC 5.4V 5.4V LDO LDO – 4.8V – INTV SGND CC operaTion Main Control Loop The ...
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LTC3787 operaTion INTV /EXTV Power CC CC Power for the top and bottom MOSFET drivers and most other internal circuitry is derived from the INTV When the EXTV pin is tied to a voltage less than 4.8V, CC the VBIAS ...
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In forced continuous operation or when clocked by an external clock source to use the phase-locked loop (see the Frequency Selection and Phase-Locked Loop section), the inductor current is allowed to reverse at light loads or under large transient ...
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LTC3787 operaTion multiple LTC3787s can be configured for 2-, 3 and 12-phase operation. Table 1. V CONTROLLER 2 PHASE (°C) PHASMD GND 180 Floating 180 INTV 240 CC CLKOUT is disabled when the controller is in shutdown ...
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The Typical Application on the first page is a basic LTC3787 application circuit. LTC3787 can be configured to use either inductor DCR (DC resistance) sensing or a discrete sense resistor (R ) for current sensing. The choice between ...
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LTC3787 applicaTions inForMaTion Sense Resistor 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 V . When ...
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To scale the maximum inductor DCR to the desired sense resistor value, use the divider ratio: R SENSE(EQUIV DCR at T MAX L(MAX usually selected the range of 0.1μF to ...
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LTC3787 applicaTions inForMaTion Power MOSFET Selection Two external power MOSFETs must be selected for each controller in the LTC3787: one N-channel MOSFET for the bottom (main) switch, and one N-channel MOSFET for the top (synchronous) switch. The peak-to-peak gate drive ...
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C and C Selection IN OUT The input ripple current in a boost converter is relatively low (compared with the output ripple current), because this current is continuous. The input capacitor C should comfortably exceed the maximum input ...
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LTC3787 applicaTions inForMaTion Tying the PHASMD pin to INTV CC generates a phase difference (between PLLIN/MODE and CLKOUT) of 240°, 60° or 90°, respectively, and a phase difference (between CH1 and CH2) of 120°, 180° V OUT V OUT 0,180 ...
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Setting Output Voltage The LTC3787 output voltage is set by an external feedback resistor divider carefully placed across the output, as shown in Figure 5. The regulated output voltage is determined by: ...
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LTC3787 applicaTions inForMaTion EXTV remains above 4.55V. The EXTV CC to regulate the INTV voltage to 5.4V, so while EXTV CC is less than 5.4V, the LDO is in dropout and the INTV voltage is approximately equal to EXTV is ...
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Phase-Locked Loop and Frequency Synchronization The LTC3787 has an internal phase-locked loop (PLL) comprised of a phase frequency detector, a lowpass filter and a voltage-controlled oscillator (VCO). This allows the turn-on of the bottom MOSFET of channel 1 ...
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LTC3787 applicaTions inForMaTion Minimum On-Time Considerations Minimum on-time the smallest time duration ON(MIN) that the LTC3787 is capable of turning on the bottom MOSFET determined by internal timing delays and the gate charge required to ...
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Checking Transient Response The regulator loop response can be checked by looking at the load current transient response. Switching regulators take several cycles to respond to a step in DC (resistive) load current. When a load step occurs, ...
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LTC3787 applicaTions inForMaTion A 6.8μH inductor will produce a 31% ripple current. The peak inductor current will be the maximum DC value plus one half the ripple current, or 9.25A. The R resistor value can be calculated by using the ...
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Figure 8. Recommended Printed Circuit Layout Diagram BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. – SENSE1 ILIM + SENSE1 PGOOD V PULL-UP SW1 TG1 LTC3787 C B1 ...
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LTC3787 applicaTions inForMaTion PC Board Layout Debugging Start with one controller time helpful to use a DC-50MHz current probe to monitor the current in the inductor while testing the circuit. Monitor the output switching node ...
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Typical applicaTions – SENSE1 + SENSE1 ILIM PHASMD CLKOUT PLLIN/MODE SGND EXTV CC LTC3787 RUN FREQ C , 0.1µ 15nF ITH R , 8.66k ITH ITH C , 220pF ITHA R , 12.1k A VFB + ...
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LTC3787 Typical applicaTions SENSE1 SENSE1 ILIM PHASMD CLKOUT PLLIN/MODE SGND EXTV CC RUN FREQ C , 0.1µ 15nF ITH R , 3.57k ITH ITH C , 220pF ITHA R , 12.1k A VFB SENSE2 SENSE2 R ...
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Typical applicaTions 53. 26.1k 1% SENSE1 C1 0.1µF SENSE1 C3 ILIM 0.1µF PHASMD CLKOUT PLLIN/MODE INTV CC SGND EXTV R , 41.2k RUN FREQ FREQ C , 0.1µ 15nF ITH ...
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LTC3787 Typical applicaTions ILIM PHASMD PLLIN/MODE INTV CC SGND EXTV CC RUN FREQ C , 0.1µ 15nF ITH R , 8.66k ITH ITH C , 220pF ITHA R , 12.1k A VFB R B CLKOUT 232k ...
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DescripTion .254 MIN .0165 ± .0015 RECOMMENDED SOLDER PAD LAYOUT .0075 – .0098 (0.19 – 0.25) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *DIMENSION ...
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LTC3787 package DescripTion 4.50 ± 0.05 3.10 ± 0.05 2.50 REF 2.65 ± 0.05 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED PIN 1 TOP MARK (NOTE 6) 5.00 ...
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... Updated Figures 11, 12, 13 Updated Related Parts 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. and EXTV ...
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... Wide Input Range LTC1871-7 Flyback, Boost and SEPIC Controller LT3757/LT3758 Boost, Flyback, SEPIC and Inverting Controller LTC3789 High Efficiency Synchronous 4-Switch Buck-Boost DC/DC Controller 36 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 12V ...