LT3991EMSE#PBF Linear Technology, LT3991EMSE#PBF Datasheet

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... The LT3991 is available in small 10-pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance. L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ...

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... JA JC EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LT3991EDD#PBF LT3991EDD#TRPBF LT3991IDD#PBF LT3991IDD#TRPBF LT3991EMSE#PBF LT3991EMSE#TRPBF LT3991IMSE#PBF LT3991IMSE#TRPBF LT3991EMSE-3.3#PBF LT3991EMSE-3.3#TRPBF LTFRS LT3991IMSE-3.3#PBF LT3991IMSE-3.3#TRPBF LT3991EMSE-5#PBF LT3991EMSE-5#TRPBF LT3991IMSE-5#PBF LT3991IMSE-5#TRPBF Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. ...

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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T PARAMETER Minimum Input Voltage Quiescent Current from V IN LT3991 FB Pin Current Internal Feedback Resistor Divider Feedback Voltage LT3991-3.3 Output Voltage LT3991-5 Output Voltage FB Voltage Line Regulation Switching Frequency ...

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LT3991/LT3991-3.3/LT3991-5 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency OUT 100 V = 12V 24V 36V 48V OUT ...

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TYPICAL PERFORMANCE CHARACTERISTICS Maximum Load Current 3 3.3V OUT 2.5 TYPICAL 2.0 MINIMUM 1.5 1.0 0 INPUT VOLTAGE (V) 3991 G08 Switching Frequency 1000 950 900 850 ...

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LT3991/LT3991-3.3/LT3991-5 TYPICAL PERFORMANCE CHARACTERISTICS LT3991-X Frequency Foldback 900 800 700 600 500 400 300 200 100 REGULATION VOLTAGE) OUT 3991 G30 Minimum Input Voltage 5 3.3V OUT 4.8 4.6 ...

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TYPICAL PERFORMANCE CHARACTERISTICS Transient Load Response, Load Current Stepped from 0. OUT 100mV/ DIV I L 500mA/ DIV 10µs/DIV 3991 G25 V = 48V 3.3V IN OUT C = 47µF OUT PIN FUNCTIONS BD (Pin ...

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LT3991/LT3991-3.3/LT3991-5 PIN FUNCTIONS PG (Pin 9): The PG pin is the open-drain output of an internal comparator. PGOOD remains low until the FB pin is within 9% of the final regulation voltage. PGOOD is valid when the LT3991 is enabled ...

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OPERATION The LT3991 is a constant frequency, current mode step- down regulator. An oscillator, with frequency set by RT, sets an RS flip-flop, turning on the internal power switch. An amplifier and comparator monitor the current flowing between the V ...

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LT3991/LT3991-3.3/LT3991-5 APPLICATIONS INFORMATION performance of the LT3991. The feedback resistors should preferably be on the order of MΩ and the Schottky catch diode should have less than 1µA of typical reverse leak- age at room temperature. These two considerations are ...

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APPLICATIONS INFORMATION Operating Frequency Tradeoffs Selection of the operating frequency is a tradeoff between efficiency, component size, minimum dropout voltage, and maximum input voltage. The advantage of high frequency operation is that smaller inductor and capacitor values may be used. ...

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... For details of maximum output current and discontinuous operation, see Linear Technology’s Application Note 44. Finally, for duty cycles greater than 50% (V TYPE a minimum inductance is required to avoid sub-harmonic Open oscillations ...

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APPLICATIONS INFORMATION Input Capacitor Bypass the input of the LT3991 circuit with a ceramic capacitor of X7R or X5R type. Y5V types have poor performance over temperature and applied voltage, and should not be used. A 4.7μF to 10μF ceramic ...

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LT3991/LT3991-3.3/LT3991-5 APPLICATIONS INFORMATION Table 4. Schottky Diodes. The Reverse Current Values Listed Are Estimates Based Off of Typical Curves for Reverse Current vs Reverse Voltage at 25° AVE F PART NUMBER (V) (A) (mV) ...

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APPLICATIONS INFORMATION while using the internal boost diode. For reliable BOOST pin operation with 2.5V outputs use a good external Schottky diode (such as the ON Semi MBR0540), and a 1μF boost capacitor (Figure 3b). For output voltages below 2.5V, ...

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LT3991/LT3991-3.3/LT3991-5 APPLICATIONS INFORMATION At light loads, the inductor current becomes discontinu- ous and this reduces the minimum input voltage to ap- proximately 400mV above higher load currents, OUT the inductor current is continuous and the duty cycle ...

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APPLICATIONS INFORMATION Soft-Start The SS pin can be used to soft-start the LT3991 by throttling the maximum input current during start-up. An internal 1μA current source charges an external capacitor generating a voltage ramp on the SS pin. The SS ...

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... If the input supply is poorly controlled or the user will be plugging the LT3991 into an energized supply, the input network should be designed to prevent this overshoot. See Linear Technology Application Note 88 for a complete discussion. High Temperature Considerations For higher ambient temperatures, care should be taken in the layout of the PCB to ensure good heat sinking of the LT3991 ...

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... LT3991/LT3991-3.3/LT3991-5 avoid excessive increase in light load supply current at high temperatures. Other Linear Technology Publications Application Notes 19, 35 and 44 contain more detailed descriptions and design information for buck regulators and other switching regulators. The LT1376 data sheet has a more extensive discussion of output ripple, loop compensation and stability testing ...

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LT3991/LT3991-3.3/LT3991-5 TYPICAL APPLICATIONS 4.3V TO 37V 16V TO 55V 3.3V Step-Down Converter with Undervoltage Lockout, Soft-Start, and Power Good 55V 4.7µF 20 1.8V Step-Down Converter BOOST OFF ...

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TYPICAL APPLICATIONS 4V Step-Down Converter with a High Impedance Input Source R + 10M 48V – BULK 432k 100µF 4.7µF Sourcing a Maximum Load Pulse V IN 10V/DIV V OUT 200mV/DIV I L 1A/DIV 500µs/DIV LT3991/LT3991-3.3/LT3991 ...

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LT3991/LT3991-3.3/LT3991-5 PACKAGE DESCRIPTION 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). ...

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... Added 3.3V and 5V fixed voltage options reflected throughout the data sheet. 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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... I <1 µA, OUT(MIN 1.21V 2.5µA, I <1 µA, OUT(MIN 1.21V 2.8µA, I <1 µA, OUT(MIN 0.8V 75µA, I <1 µA, OUT(MIN 0.8V 75µA, OUT(MIN 0.78V 70µA, OUT(MIN 0.78V 85µA, OUT(MIN) Q 3991fa LT 0211 REV A • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2009 ...