ltc3716 Linear Technology Corporation, ltc3716 Datasheet
ltc3716
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ltc3716 Summary of contents
Page 1
... SENSE1 TG2 BOOST2 0.47 F SW2 BG2 INTV SENSE2 10 F – SENSE2 Figure 1. High Current Dual Phase Step-Down Converter LTC3716 2-Phase, 5-Bit VID, Switching Regulator U 3716 is a 2-phase, VID programmable, synchro- TM operation for highest efficiency 28V 10 F 35V 4 0.002 ...
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... Measured at V EAIN V Ramping Down 1.2V, Sink/Source 5 A (Note 1.2V, (g • Ext Load) (Note ORDER PART TOP VIEW NUMBER 1 PGOOD 36 2 TG1 35 LTC3716EG 3 SW1 34 4 BOOST1 BG1 31 7 EXTV INTV PGND 28 10 ...
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... Ramping Positive 20mA, EXTV Ramping Negative CC CC (Note 8) V < VID0–VID4 < 7V BIAS V = 1.2V PLLFLTR PLLFLTR V 2.4V PLLFLTR f < f PLLIN OSC f > f PLLIN OSC LTC3716 = 5V unless otherwise noted. MIN TYP MAX UNITS 1 – 0.5 –1.2 1.0 1.5 1.9 4.1 4.5 0 1.6 5 – 85 – 99 ...
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... P according to the following formula: D LTC3716EG • Note 4: The LTC3716 is tested in a feedback loop that servos V specified voltage and measures the resultant V 4 The denotes the specifications which apply over the full operating = 15V 5V BIAS ...
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... CURRENT (mA) 3716 G05 Maximum Current Sense Threshold vs Duty Factor 100 DUTY FACTOR (%) 3716 G08 LTC3716 Efficiency vs Input Voltage (Figure 13) 100 I = 20A OUT V = 1.6V OUT INPUT VOLTAGE (V) 3716 G03 INTV and EXTV ...
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... LTC3716 W U TYPICAL PERFOR A CE CHARACTERISTICS Maximum Current Sense Threshold vs V (Soft-Start) RUN/ 1.6V SENSE(CM (V) RUN/SS 3716 G10 Load Regulation 0.0 FCB = 15V IN FIGURE 1 –0.1 –0.2 –0.3 –0 LOAD CURRENT (A) 3716 G13 ...
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... TEMPERATURE ( C) 3716 G21 V Thresholds vs Temperature 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 100 125 –50 3716 G23 LTC3716 Constant Frequency Mode (Figure 13 15V 1.6V 400mA IN OUT L V OUT(AC) 20mV/DIV I L1 1A/DIV I L2 1A/DIV FCB = INTV R9, R21 = 0. s/DIV 3716 G25 Oscillator Frequency vs Temperature ...
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... LTC3716 CTIO S RUN/SS (Pin 1): Combination of Soft-Start, Run Control Input and Short-Circuit Detection Timer. A capacitor to ground at this pin sets the ramp time to full current output. Forcing this pin below 0.8V causes the IC to shut down all internal circuitry. All functions are disabled in shutdown. ...
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... SLOPE 45k 45k COMP 2.4V – 1.2 A SHDN RUN RST SOFT START FB 5-BIT VID DECODER TYPICAL ALL VID PINS 40k VID1 VID2 VID3 VID4 V BIAS LTC3716 INTV BOOST TOP D1 SW INTV CC LOGIC BG BOT PGND R SENSE INTV ...
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... U OPERATIO (Refer to Functional Diagram) Main Control Loop The LTC3716 uses a constant frequency, current mode step-down architecture with the two output stages oper- ating 180 degrees out of phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, and turned off when the main current comparator resets the RS latch ...
Page 11
... RUN/SS capacitor, the controller will be shut down until the RUN/SS pin voltage is recycled. This built-in latchoff can be overidden by providing a current > compli- ance the RUN/SS pin. This current shortens the LTC3716 pin to bypass the internal resistors and CC 11 ...
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... Foldback current limiting is acti APPLICATIO S I FOR ATIO The basic LTC3716 application circuit is shown in Figure 1 on the first page. External component selection begins with the selection of the inductors based on ripple current requirements and continues with the current sensing resistors using the calculated peak inductor current and/or maximum current limit ...
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... Because they lack a bobbin, mounting is more difficult. However, designs for surface mount are available which do not increase the height significantly. Power MOSFET, D1 and D2 Selection Two external power MOSFETs must be selected for each output stage with the LTC3716: one N-channel MOSFET 0.7 0.8 0 ...
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... Selection criteria for the power MOSFETs include the “ON” resistance R , reverse transfer capacitance C DS(ON) input voltage and maximum output current. When the LTC3716 is operating in continuous mode the duty factors for the top and bottom MOSFETs of each output stage are given by: V OUT ...
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... Sanyo OS-CON, POSCAPs, Panasonic SP caps, Nichicon PL series and Sprague 595D series. Consult the manufac- OUT turer for other specific recommendations. A combination = of capacitors will often result in maximizing performance OUT = combined inductor and minimizing overall cost and size. LTC3716 with I = 0.4I /2 assuming OUT(MAX) ) and SENSE ...
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... MOSFET gate drivers. High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the maxi- mum junction temperature rating for the LTC3716 to be exceeded. The supply current is dominated by the gate charge supply current, in addition to the current drawn from the differential amplifier output ...
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... If the input current does not change then the efficiency has not changed either. Output Voltage The LTC3716 has a true remote voltage sense capablity. The sensing connections should be returned from the load back to the differential amplifier’s inputs through a com- mon, tightly coupled pair of PC traces. The differential amplifier corrects for DC drops in both the power and ground paths ...
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... The time for the output current to ramp up is then: 1 0.950V 0 0.925V 1 0.900V t IRAMP 0 0.875V 1 0.850V By pulling the RUN/SS pin below 0.8V the LTC3716 is put 0 0.825V into low current shutdown (I 1 0.800V can be driven directly from logic as shown in Figure 6. 0 0.775V Diode D1 in Figure 6 reduces the start delay but allows 1 0.750V C to ramp up slowly providing the soft-start function ...
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... F will be sufficient for most applications. SS Phase-Locked Loop and Frequency Synchronization The LTC3716 has a phase-locked loop comprised of an internal voltage controlled oscillator and phase detector. This allows the top MOSFET turn- locked to the rising edge of an external source. The frequency range of ...
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... Minimum On-Time Considerations Minimum on-time the smallest time duration ON(MIN) that the LTC3716 is capable of turning on the top MOSFET determined by internal timing delays and the gate charge required to turn on the top MOSFET. Low duty cycle applications may approach this minimum on-time limit ...
Page 21
... The open-loop DC gain of the control loop is reduced depending upon the maximum load step specifications. Active voltage positioning can easily be added to the LTC3716 by loading the I a resistive divider having a Thevenin equivalent voltage source equal to the midpoint operating voltage of the error amplifier ...
Page 22
... ESR at IN the switching frequency. A 50W supply will typically require a minimum of 200 F to 300 F of output capaci- tance having a maximum of 10m to 20m of ESR. The LTC3716 2-phase architecture typically halves the input and output capacitance requirements over competing solutions ...
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... R SENSE LTC3716 The power dissipation on the topside MOSFET can be easily estimated. Using a Siliconix Si4420DY for example 0.013 , C 3716 F09 DS(ON) voltage with T temperature: LTC3716 . DSS = 5V (nominal 1.2V 20A and f = 300kHz. MAX A pin for 300kHz operation. The minimum CC V ...
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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 LTC3716. Check the following in your layout: 1) Are the signal and power grounds separate? The signal ground traces should return to Pin 9 first. Connect Pin 9 ...
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... PC trace spacing? The filter capacitors between + – SENSE and SENSE pin pairs should be as close as possible to the LTC3716. Ensure accurate current sensing with Kelvin connections at the current sense resistor. See Figure 10. 4) Does the (+) plate of C connect to the drains of the IN topside MOSFETs as closely as possible? This capacitor provides the AC current to the MOSFETs ...
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... LTC3716 U U APPLICATIO S I FOR ATIO of the input capacitor(s) with a short isolated PC trace since very high switched currents are present. A separate isolated path from the negative plate(s) of the input capacitor(s) should be used to tie in the IC power ground pin (PGND) and the signal ground pin (SGND). This ...
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... U TYPICAL APPLICATIO Figure 13 shows a typical application using LTC3716 to power the mobile CPU core. The input can vary from 7V to 24V, the output voltage can be programmed from 0.6V to 1.75V with a maximum current of 30A. This power supply receives three input signals to generate different output voltage offsets based on the operation conditions ...
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... LTC3716 PACKAGE DESCRIPTIO 5.20 – 5.38** (.205 – .212) .13 – .22 .55 – .95 (.005 – .009) (.022 – .037) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 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 ...