ltc3850gn-2 Linear Technology Corporation, ltc3850gn-2 Datasheet
ltc3850gn-2
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ltc3850gn-2 Summary of contents
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FEATURES n Dual, 180° Phased Controllers Reduce Required Input Capacitance and Power Supply Induced Noise n High Effi ciency 95 DCR Current Sensing SENSE ±1% 0.8V Output Voltage Accuracy n n Phase-Lockable Fixed Frequency 250kHz ...
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... For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: 2 PIN CONFIGURATION ) < 500ms, with , CC to –0.3V CC PART MARKING PACKAGE DESCRIPTION LTC3850GN-2 28-Lead Narrow Plastic SSOP http://www.linear.com/leadfree/ http://www.linear.com/tapeandreel/ TOP VIEW 1 28 FREQ/PLLFLTR RUN1 + 2 ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T SYMBOL PARAMETER Main Control Loops V Regulated Feedback Voltage FB1,2 I Feedback Current FB1,2 V Reference Voltage Line Regulation REFLNREG V Output Voltage Load Regulation LOADREG g Transconductance Amplifi er ...
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LTC3850-2 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T SYMBOL PARAMETER Oscillator and Phase-Locked Loop f Nominal Frequency NOM f Lowest Frequency LOW f Highest Frequency HIGH R MODE/PLLIN Input Resistance MODE/PLLIN I Phase Detector Output Current FREQ ...
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TYPICAL PERFORMANCE CHARACTERISTICS Load Step (Burst Mode Operation) I LOAD 2A/DIV 200mA TO 2. 2A/DIV V OUT 100mV/DIV AC COUPLED 40μs/DIV CIRCUIT OF FIGURE 12V 1.8V IN OUT Load Step (Pulse-Skipping Mode) I ...
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LTC3850-2 TYPICAL PERFORMANCE CHARACTERISTICS Tracking Up and Down with External Ramp TK/SS1 TK/SS2 2V/DIV V OUT1 3.3V 3Ω LOAD 1V/DIV V OUT2 1.8V 1.5Ω LOAD 1V/DIV 38502 G10 10ms/DIV Current Sense Threshold vs I Voltage ...
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TYPICAL PERFORMANCE CHARACTERISTICS Shutdown (RUN) Threshold vs Temperature 1.5 1.4 1.3 ON 1.2 OFF 1.1 1.0 –50 – TEMPERATURE (°C) 38502 G18 Undervoltage Lockout Threshold (INTV ) vs Temperature RISING 3 FALLING 2 ...
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LTC3850-2 PIN FUNCTIONS RUN1, RUN2 (Pin 1, Pin 13): Run Control Inputs. A voltage above 1.2V on either pin turns on the IC. However, forcing either of these pins below 1.2V causes the IC to shut down that particular channel. ...
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FUNCTIONAL DIAGRAM FREQ/PLLFLTR MODE/PLLIN MODE/SYNC DETECT PLL-SYNC OSC – I CMP + – SLOPE COMPENSATION INTV CC 1 SLOPE RECOVERY 51k ACTIVE CLAMP I THB SLEEP V IN 0.8V REF EA – – ...
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LTC3850-2 OPERATION Main Control Loop The LTC3850 constant-frequency, current mode step-down controller with two channels operating 180 degrees out-of-phase. During normal operation, each top MOSFET is turned on when the clock for that channel sets the RS latch, ...
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OPERATION mode of operation, tie the MODE/PLLIN pin to INTV select Burst Mode operation, fl oat the MODE/PLLIN pin. When a controller is enabled for Burst Mode operation, the peak current in the inductor is set to approximately one-third of ...
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LTC3850-2 APPLICATIONS INFORMATION The Typical Application on the fi rst page is a basic LTC3850- 2 application circuit. LTC3850-2 can be confi gured to use either DCR (inductor resistance) sensing or low value resis- tor sensing. The choice between the ...
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APPLICATIONS INFORMATION sets the peak of the inductor current, yielding a maximum average output current I equal to the peak value less MAX half the peak-to-peak ripple current, ΔI sense resistor value, use the equation: V SENSE(MAX ΔI ...
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... RLC meter, but the DCR tolerance is not always the same and varies with temperature; consult the manufacturers’ datasheets for detailed information. Using the inductor ripple current value from the Inductor Value Calculation section, the target sense resistor value is: ...
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APPLICATIONS INFORMATION sense resistors. Light load power loss can be modestly higher with a DCR network than with a sense resistor, due to the extra switching losses incurred through R1. However, DCR sensing eliminates a sense resistor, reduces conduc- tion ...
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LTC3850-2 APPLICATIONS INFORMATION Selection criteria for the power MOSFETs include the on-resistance R , Miller capacitance C DS(ON) voltage and maximum output current. Miller capacitance can be approximated from the gate charge curve MILLER usually provided on the ...
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APPLICATIONS INFORMATION to TK/SS = 0.64V. Between TK/SS = 0.64V and 0.74V, it will operate in forced continuous mode and revert to the selected mode once TK/SS > 0.74V. The output ripple is minimized during the 100mV forced continuous mode ...
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LTC3850-2 APPLICATIONS INFORMATION TIME (5a) Coincident Tracking Figure 5. Two Different Modes of Output Voltage Tracking V OUT1 TK/SS2 PIN R4 R2 (6a) Coincident Tracking Setup Figure 6. Setup for Coincident and Ratiometric Tracking 18 V OUT1 ...
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APPLICATIONS INFORMATION High input voltage applications in which large MOSFETs are being driven at high frequencies may cause the maxi- mum junction temperature rating for the LTC3850 exceeded. The INTV current, which is dominated CC by the gate ...
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LTC3850-2 APPLICATIONS INFORMATION Topside MOSFET Driver Supply (C External bootstrap capacitors C connected to the BOOST B pins supply the gate drive voltages for the topside MOSFETs. Capacitor C in the Functional Diagram is charged though B external diode DB ...
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APPLICATIONS INFORMATION both controllers are operating due to the reduced overlap of current pulses required through the input capacitor’s ESR. This is why the input capacitor’s requirement calculated above for the worst-case controller is adequate for the dual controller design. ...
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LTC3850-2 APPLICATIONS INFORMATION of controller 2’s top MOSFET is thus 180 degrees out- of-phase with the external clock. The phase detector is an edge sensitive digital type that provides zero degrees phase shift between the external and internal oscillators. This ...
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APPLICATIONS INFORMATION on the current sense signal. The minimum on-time can be affected by PCB switching noise in the voltage and current loop. As the peak sense voltage decreases the minimum on-time gradually increases to 130ns. This is of particular ...
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LTC3850-2 APPLICATIONS INFORMATION a minimum of 20μF to 40μF of capacitance having a maximum of 20mΩ to 50mΩ of ESR. The LTC3850-2 2-phase architecture typically halves this input capacitance requirement over competing solutions. Other losses including Schottky conduction losses during ...
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APPLICATIONS INFORMATION 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 12. Figure ...
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LTC3850-2 APPLICATIONS INFORMATION f IN Figure 12. Recommended Printed Circuit Layout Diagram BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH. 26 TK/SS1 R PU2 V PULL-UP I PGOOD PGOOD TH1 ...
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APPLICATIONS INFORMATION 4.7μF M1 0.1μF L1 3.3μH 6.19k 1% 1.33k 1% 33pF V OUT1 3.3V 5A 63.4k 1800pF 1% C OUT1 20k 4.75k 100μ L1, L2: COILTRONICS HCP0703 M1, M2: VISHAY SILICONIX Si4816BDY ...
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LTC3850-2 APPLICATIONS INFORMATION Design Example As a design example for a two channel medium current regu- lator, assume V = 12V(nominal 3.3V 1.8V, I OUT1 OUT2 MAX1,2 (see Figure 14). The regulated output voltages ...
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APPLICATIONS INFORMATION The power loss the maximum input voltage is: − • V IN(MAX) OUT P R1= LOSS R1 (20V − 3.3V) • 3.3V = 9mW 6.19k The respective values for Channel 2 are ...
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LTC3850-2 TYPICAL APPLICATIONS 4.7μ 2.2μH 6mΩ 15pF V OUT1 3.3V 5A 63.4k 1% 1000pF + 20k C 10k OUT1 1% 1% 220μF L1: TDK RLF 7030T-2R2M5R4 L2: TDK ULF10045T-3R3N6R9 C : SANYO 4TPE220MF OUT1 C : SANYO 6TPE150MI ...
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TYPICAL APPLICATIONS LTC3850-2 38502f 31 ...
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LTC3850-2 TYPICAL APPLICATIONS 32 38502f ...
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TYPICAL APPLICATIONS 4.7μF M1 0.1μF L1 0.75μH 1.2k 1% 2.94k 1% 47pF V OUT1 1.8V 5A 25.5k 2200pF 1% C 20k 14k OUT1 100μ L1, L2: TOKO FDV0630 0.75μH M1, M2: VISHAY SILICONIX Si4816BDY ...
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LTC3850-2 TYPICAL APPLICATIONS 2.2Ω V IN1 12V 4.7μF 4.7μF M1 0.1μF L1 2.2μH 3.74k 1% 1.40k 1% 47pF V OUT1 2.5V 5A 43.2k 2200pF 1% C OUT1 20k 10k 100μ L1: TOKO FDV0630 2.2μH L2: TOKO FDV0630 ...
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... FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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. ...
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... LT3845 Low I , High Voltage Single Output Synchronous Step-Down Q DC/DC Controller LTC3851 High Effi ciency Synchronous Step-Down Switching Regulator Controller PolyPhase is a registered trademark of Linear Technology Corporation Linear Technology Corporation 36 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 10k RUN 0.1μ ...