LTC3809 Linear Technology, LTC3809 Datasheet
LTC3809
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LTC3809 Summary of contents
Page 1
... MOSFETs using few external components. The constant frequency current mode architecture with MOSFET V sensing eliminates the need for a current sense resistor and improves effi ciency. For noise sensitive applications, the LTC3809 can be exter- nally synchronized from 250kHz to 750kHz. Burst Mode is IN inhibited during synchronization or when the SYNC/MODE pin is pulled low to reduce noise and RF interference ...
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... LTC3809EMSE#PBF LTC3809EMSE#TRPBF LEAD BASED FINISH TAPE AND REEL LTC3809EDD LTC3809EDD#TR LTC3809EMSE LTC3809EMSE#TR Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ...
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... A Note 4: Dynamic supply current is higher due to gate charge being delivered at the switching frequency. Note 5: The LTC3809 is tested in a feedback loop that servos I specifi ed voltage and measures the resultant V Note 6: Peak current sense voltage is reduced dependent on duty cycle to a percentage of value as shown in Figure 1. ...
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... LTC3809 TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency vs Load Current www.datasheet4u.com 100 FIGURE 10 CIRCUIT V = 2.5V OUT 3.3V OUT 1.2V OUT 1.8V OUT SYNC/MODE = 100 1k LOAD CURRENT (mA) Load Step (Burst Mode Operation) V OUT 200mV/DIV AC COUPLED I L 2A/DIV 1.8V OUT I = 300mA TO 3A ...
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... Shutdown Quiescent Current vs Input Voltage INPUT VOLTAGE (V) 3809 G14 LTC3809 T = 25°C unless otherwise noted. A Shutdown (RUN) Threshold vs Temperature 1.20 1.15 1.10 1.05 1. 100 –60 –40 – TEMPERATURE (°C) 3809 G09 Oscillator Frequency vs Temperature ...
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... LTC3809 PIN FUNCTIONS PLLLPF (Pin 1): Frequency Set/PLL Lowpass Filter. When synchronizing to an external clock, this pin serves as the lowpass fi lter point for the phase-locked loop. Normally, www.datasheet4u.com a series RC is connected between this pin and ground. When not synchronizing to an external clock, this pin serves as the frequency select input. Tying this pin to GND selects 300kHz operation ...
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... PLLLPF IPRG SLOPE CLK ICMP R + SENSE – UVSD + V IN SLEEP 0.15V – BURSTDIS 0.3V PHASE + – CLK LTC3809 TG 8 GND SWITCHING SW LOGIC AND ANTI-SHOOT- 10 BLANKING THROUGH CIRCUIT FCB + OV I REV – 0.68V + 0.54V UV – ...
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... IRCMP, or the beginning of the next cycle. Shutdown and Soft-Start (RUN Pin) The LTC3809 is shut down by pulling the RUN pin low. In shutdown, all controller functions are disabled and the chip draws only 9μA. The TG output is held high (off) and the BG output low (off) in shutdown. Releasing the RUN pin allows an internal 0.7μ ...
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... Frequency Selection and Phase-Locked Loop set voltage between 0.4V and several hundred mV below V , the LTC3809 operates in PWM pulse-skipping mode IN at light loads. In this mode, the current comparator ICMP may remain tripped for several cycles and force the external P-channel MOSFET to stay off for the same number of cycles ...
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... SYNC/MODE pin. In this case, a series RC should be connected between the PLLLPF pin and GND to serve as the PLL’s loop fi lter. The LTC3809 phase detector adjusts the voltage on the PLLLPF pin to align the turn-on of the external P-channel MOSFET to the rising edge of the synchronizing signal. The typical capture range of the LTC3809’ ...
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... OPERATION (Refer to Functional Diagram) Peak Current Sense Voltage Selection and Slope Compensation (IPRG Pin) www.datasheet4u.com When the LTC3809 controller is operating below 20% duty cycle, the peak current sense voltage (between the V and SW pins) allowed across the external P-channel IN MOSFET is determined by: V – ITH Δ ...
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... MOSFET ( 2.5V) is required for applications that work close to GS this voltage. When these MOSFETs are used, make sure that the input supply to the LTC3809 is less than the absolute maximum MOSFET V rating, which is typically 8V. GS The P-channel MOSFET’s on-resistance is chosen based on the required load current ...
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... IN The power dissipated in the MOSFET strongly depends on its respective duty cycles and load current. When the LTC3809 is operating in continuous mode, the duty cycles for the MOSFETs are: Top P-Channel Duty Cycle = Bottom N-Channel Duty Cycle = The MOSFET power dissipations at maximum output ...
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... trade-off OSC Burst Mode Operation Considerations The choice of R the load current at which the LTC3809 enters Burst Mode operation. When bursting, the controller clamps the peak inductor current to approximately: I BURST PEAK The corresponding average current depends on the amount of ripple current. Lower inductor values (higher ...
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... The output ripple is highest at maximum input voltage since I increase with input voltage. RIPPLE Setting Output Voltage The LTC3809 output voltage is set by an external feed- back resistor divider carefully placed across the output, as shown in Figure 3. The regulated output voltage is determined by: ⎛ ...
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... R capacitor Run and Soft-Start Functions The LTC3809 has a low power shutdown mode which is controlled by the RUN pin. Pulling the RUN pin below 1.1V puts the LTC3809 into a low quiescent current shutdown mode (I = 9μA). Releasing the RUN pin, an internal 0.7μA ...
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... An external resistor divider from V ⎛ ⎞ ⎜ ⎟ • ⎝ ⎠ drops below this value, the SYNC/MODE voltage is again above its minimum LTC3809 L1 1 SYNC/MODE Figure 7. Auxilliary Output Loop Connection to AUX : AUX(MIN) V AUX + 1μF V OUT + C OUT 3809 F07 ...
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... In this case, there is no current path from input supply (V excessive MOSFET and inductor heating. Low Input Supply Voltage Although the LTC3809 can function down to below 2.4V, the maximum allowable output current is reduced as V decreases below 3V. Figure 9 shows the amount of change 3809 F08b as the supply is reduced down to 2 ...
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... Minimum On-Time Considerations Minimum on-time the smallest amount of time ON(MIN) that the LTC3809 is capable of turning the top P-channel MOSFET on determined by internal timing delays and the gate charge required to turn on the top MOSFET. Low duty cycle and high frequency applications may approach ...
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... The short circuit current is the inductor current rating should be higher than 5.3A. The PLLLPF pin will be left fl oating, so the LTC3809 will operate at its default frequency of 550kHz. For continuous Burst Mode operation with 600mA I minimum inductor value is: L MIN . No regulator can OUT A 6A 2.2μ ...
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... APPLICATIONS INFORMATION PC Board Layout Checklist When laying out the printed circuit board, use the following www.datasheet4u.com checklist to ensure proper operation of the LTC3809. • The power loop (input capacitor, MOSFET, inductor, output capacitor) should be as small as possible and isolated as much as possible from LTC3809. ...
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... LTC3809 TYPICAL APPLICATIONS www.datasheet4u.com 3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES) 0.25 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS TOP MARK (SEE NOTE Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) 0.675 0.05 PACKAGE OUTLINE 0.50 BSC 2.38 0.05 (2 SIDES) 1.65 0.10 3.00 0.10 (2 SIDES) (4 SIDES) PIN 1 0.200 REF 0.75 0.05 0.00 – 0.05 NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). ...
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... MAX DETAIL “A” SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LTC3809 2.06 0.102 (.081 .004) 0.29 REF 1.83 0.102 (.072 .004) 0.05 REF DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE ...
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... No R Synchronous Controller with Output Tracking SENSE PolyPhase is a trademark of Linear Technology Corporation. Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 300k 2 9 SYNCH/MODE V IN 1000pF LTC3809EDD PLLLPF TG Si3447BDV 6 IPRG 10 SW 15k ...