LT3685 LINER [Linear Technology], LT3685 Datasheet
LT3685
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LT3685 Summary of contents
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FEATURES Wide Input Range: n – Operation from 3.9V to 36V – Overvoltage Lockout Protects Circuits Through 60V Transients 4A Maximum Output Current n Integrated 30mΩ N-Channel Synchronous Switch n Low Ripple (<15mV ) Burst Mode n P ...
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LT3690 ABSOLUTE MAXIMUM RATINGS (Note 1) EN, UVLO, V Voltage (Note 2) ................................60V IN BST Voltage .............................................................55V BST Voltage Above SW Voltage ...............................30V BIAS, PG Voltage . ....................................................30V FB, RT, SS, SYNC Voltage . .......................6V C CCINT ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T PARAMETER Boost Schottky Diode Drop (V – BIAS BST BST Voltage (Note 5) (V – BST SW BST Pin Current BST Pin Leakage HS Switch Drop (V ...
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LT3690 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T PARAMETER V Source Current C V Sink Current C V Pin to Switch Current Gain C Transconductance V Switching Threshold C V Clamp Voltage C Programmable Switching Frequency Note 1: ...
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TYPICAL PERFORMANCE CHARACTERISTICS Efficiency and Power Loss 100 0.5 1 1.5 2 LOAD CURRENT (A) Efficiency and Power Loss 100 0.5 1 1.5 2 LOAD CURRENT ...
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LT3690 TYPICAL PERFORMANCE CHARACTERISTICS Switch Current Limit vs Duty Cycle > 0.75V DUTY CYCLE (%) 3690 G08 BST Pin Current 120 ...
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TYPICAL PERFORMANCE CHARACTERISTICS EN Pin Current PIN VOLTAGE (V) 3690 G17 UVLO Pin Current vs Temperature (V = 1.33V) UVLO –1.4 –1.6 –1.8 ...
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LT3690 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency vs Temperature 650 R = 32.4k T 630 610 590 570 550 –50 – 100 TEMPERATURE (°C) 3690 G26 CCINT ...
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PIN FUNCTIONS SW (Pins 1-4, 23-26, Exposed Pad Pin 27): The SW pin is the emitter output of the internal highside NPN power switch (HS) and the drain output of the internal lowside power N-channel switch (LS). Connect this pin ...
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LT3690 BLOCK DIAGRAM GND REFERENCE 2µA SLEEP V MONITOR IN TEMPERATURE MONITOR UVLO 12 SYNC OSCILLATOR 5 SYNC 0.17MHz TO 1.5MHz RT 7 SOFT-START/TRACKING ...
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OPERATION The LT3690 is a constant frequency, current mode step- down regulator. An oscillator, with frequency set by R enables an RS flip-flop, turning on the internal high side (HS) power switch. An amplifier and comparator monitor the current flowing ...
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LT3690 APPLICATIONS INFORMATION FB Resistor Network The output voltage is programmed with a resistor divider between the output and the FB pin. Choose the resistor values according to: V ⎛ ⎞ OUT − 1 ⎜ ⎟ 0.8V ...
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APPLICATIONS INFORMATION Input Voltage Range The minimum input voltage is determined by either the LT3690’s minimum operating voltage of 3. its maximum duty cycle (see equation in the Operating Frequency Trade-offs section). The minimum input voltage ...
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LT3690 APPLICATIONS INFORMATION Inductor Selection and Maximum Output Current A good first choice for the inductor value is: 0.67MHz ( ) • OUT LS ƒ SW where V is the voltage drop of the low ...
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APPLICATIONS INFORMATION One approach to choosing the inductor is to start with the simple rule given above, look at the available inductors, and choose one to meet cost or space goals. Then use these equations to check that the LT3690 ...
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LT3690 APPLICATIONS INFORMATION Since the LT3690 operates at a lower current limit during Burst Mode operation, the noise is typically very quiet. If this is unacceptable, use a high performance tantalum or electrolytic capacitor at the output. Frequency Compensation The ...
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APPLICATIONS INFORMATION Low-Ripple Burst Mode and Pulse-Skipping Mode The LT3690 is capable of operating in either low ripple Burst Mode operation or pulse-skipping mode, which is selected using the SYNC pin. See the Synchronization and Mode section for details. To ...
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LT3690 APPLICATIONS INFORMATION The switching will only resume once the low side switch current has fallen below the 5A limit. This way, the com- parator regulates the valley current of the inductor to 5A during short-circuit. With properly chosen external ...
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APPLICATIONS INFORMATION 6.0 TO START 5.5 5.0 4.5 4.0 TO RUN 3.5 3 100 1000 LOAD CURRENT (mA) Figure 6. The Minimum Input Voltage Depends on Output Voltage, Load Current and Boost Circuit is also limited by the ...
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LT3690 APPLICATIONS INFORMATION LT3690 SS OUT1 0.1µF LT3690 SS OUT2 0.047µF LT3690 SS OUT1 0.22µF LT3690 SS OUT2 2V/DIV V OUT1 2V/DIV 3.3V V OUT2 2V/DIV 3690 F08a (8a) Independent Start- 2V/DIV V ...
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APPLICATIONS INFORMATION LT3690 SS OUT1 0.1µF R1 28.7k LT3690 SS OUT2 R2 10k LT3690 SS OUT1 PG1 0.1µF LT3690 SS OUT2 0.047µF 5V 2V/DIV V OUT1 2V/DIV V 3.3V OUT2 2V/DIV 3690 F09a (9a) Coincident Start-Up 5V 2V/DIV V OUT1 ...
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LT3690 APPLICATIONS INFORMATION Output Tracking and Sequencing Output tracking and sequencing between voltage regulators can be implemented using the LT3690’s SS and PG pins. Figures 8 and 9 show several configurations for output tracking and sequencing of the LT3690 and ...
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APPLICATIONS INFORMATION The UVLO circuitry prevents the regulator from operating at source voltages where the problems might occur. An internal comparator will force the part into shutdown below the fixed V UVLO threshold of 3.0V. This feature can be IN ...
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LT3690 APPLICATIONS INFORMATION PCB Layout For proper operation and minimum EMI, care must be taken during printed circuit board layout. Figure 13 shows the recommended component placement with trace, ground plane and via locations. Note that large, switched currents flow ...
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TYPICAL APPLICATIONS V IN 6.3V TO 36V 1nF V IN 4.5V TO 36V 1nF V IN 3.9V TO 36V 1nF 5V Step-Down Converter V BIAS 10µF IN UVLO PG ON OFF EN 0.68µF LT3690 SS BST ...
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LT3690 TYPICAL APPLICATIONS AUXILIARY SUPPLY 3. 3.9V TO 36V 1nF AUXILIARY SUPPLY 3. 3.9V TO 36V 10nF V IN 14V TO 36V 200k 10µF 21k 1nF SLEEP: V < 12.3V IN WAKE ...
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PACKAGE DESCRIPTION 4.50 ± 0.05 3.10 ± 0.05 4.00 ± 0.10 PIN 1 TOP MARK (NOTE 6) 6.00 ± 0.10 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS ...
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