LTC3703 Linear Technology, LTC3703 Datasheet
LTC3703
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LTC3703 Summary of contents
Page 1
... Current limit is programmable with an external resistor and utilizes the voltage drop across the synchronous MOSFET to eliminate the need for a current sense resistor. Soft- start is provided by an external capacitor. Pulling the soft-start pin low shuts down the LTC3703, reducing supply current ...
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... DRV = BOOST = 25k, unless otherwise specified. CONDITIONS RUN/ (Note 5) RUN/ (Note 5) RUN/ Voltages ............................... –0. ORDER PART TOP VIEW NUMBER 28 BOOST LTC3703EG DRV ...
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... D LTC3703 • 100 C/W) G Package Note 4: The LTC3703 is tested in a feedback loop that servos V reference voltage with the COMP pin forced to a voltage between 1V and 2V. The denotes the specifications which apply over the full operating = DRV = ...
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... LTC3703 W U TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs Input Voltage 100 OUT 0.5A OUT 12V 75 OUT f = 300kHz PULSE SKIP DISABLED INPUT VOLTAGE (V) 3703 G01 V Current vs V Voltage CC CC 3.5 3.0 COMP = 1.5V 2.5 2 1.5 1.0 0 VOLTAGE (V) ...
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... GATE CAPACITANCE (pF) 3703 G14 RUN/SS Sink Current vs SW Voltage 0.3V MAX –5 –10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 |SW| VOLTAGE (V) 3703 G17 LTC3703 Driver Peak Source Current vs Supply Voltage 3.0 2.5 2.0 1.5 1.0 0 DRV /BOOST VOLTAGE (V) CC 3703 G12 RUN/SS Pull-Up Current vs ...
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... LTC3703 W U TYPICAL PERFOR A CE CHARACTERISTICS I Current vs Temperature MAX –60 –40 – 100 TEMPERATURE ( C) 3703 G19 Shutdown Threshold vs Temperature 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –60 –40 – Duty Cycle vs COMP Voltage 100 V = 10V 75V 50V 25V 0.5 1.00 1.25 1.50 1.75 2.00 0.75 COMP (V) 3703 G20 ...
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... V be connected to a low noise power supply voltage between 9V and 15V and should be bypassed to GND (pin 8) with at least a 0.1 F capacitor in close proximity to the LTC3703. pin sets the MAX SW (Pin 13): Switch Node Connection to Inductor and Bootstrap Capacitor ...
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... N-channel MOSFETs. Its high operating volt- age capability allows it to directly step down input voltages up to 100V without the need for a step-down transformer. For circuit operation, please refer to the Functional Dia- gram of the IC and Figure 1. The LTC3703 uses voltage 8 W RSET ...
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... Fast Transient Response The LTC3703 uses a fast 25MHz op amp as an error amplifier. This allows the compensation network to be optimized for better load transient response. The high bandwidth of the amplifier, along with high switching frequencies and low value inductors, allow very high loop crossover frequencies ...
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... This soft-start scheme smoothly ramps the output voltage to its regulated value, with no overshoot. The RUN/SS voltage will continue ramping until it reaches an internal 4V clamp. Then the MIN feedback comparator is enabled and the LTC3703 is in full operation. When the RUN/SS is low, the supply current is reduced ...
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... Pulse Skip Mode The LTC3703 can operate in one of two modes selectable with the MODE/SYNC pin—Pulse Skip Mode or forced continuous mode. Pulse Skip Mode is selected when increased efficiency at light loads is desired. In this mode, the bottom MOSFET is turned off when inductor current reverses to minimize the efficiency loss due to reverse current flow ...
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... With the INV pin grounded, the LTC3703 oper- ates in buck mode with TG driving the main (top side) switch and BG driving the synchronous (bottom side) switch. If the INV pin is pulled above 2V, the LTC3703 operates in boost mode with BG driving the main (bottom side) switch and TG driving the synchronous (top side) switch ...
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... Figure 8. MODE/SYNC Clock Input and Switching Waveforms for Synchronous Operation Inductor The inductor in a typical LTC3703 circuit is chosen for a specific ripple current and saturation current. Given an input voltage range and an output voltage, the inductor value and operating frequency directly determine the ripple current ...
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... U APPLICATIO S I FOR ATIO appropriate breakdown specification. Since many high voltage MOSFETs have higher threshold voltages (typi- cally, V 6V), the LTC3703 is designed to be used GS(MIN) with 15V gate drive supply (DRV For maximum efficiency, on-resistance R capacitance should be minimized. Low R conduction losses and low input capacitance minimizes transition losses ...
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... APPLICATIO S I FOR ATIO Multiple MOSFETs can be used in parallel to lower R and meet the current and thermal requirements if desired. The LTC3703 contains large low impedance drivers ca- pable of driving large gate capacitances without signifi- cantly slowing transition times. In fact, when driving MOSFETs with very low gate charge sometimes ...
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... ESR, but can be used in cost-driven applications providing that consideration is given to ripple current ratings and long term reliability. Other capacitor types include Panasonic SP and Sanyo POSCAPs. Output Voltage The LTC3703 output voltage is set by a resistor divider according to the following formula ...
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... For best results, use an ultrafast recovery silicon diode such as the BAS21. , must internal undervoltage lockout (UVLO) monitors the voltage on DRV cient gate drive voltage. If the DRV the UVLO threshold, the LTC3703 shuts down and the gate drive outputs remain low. LTC3703 ...
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... BGRTN is 15V. If, floating the I FEEDBACK LOOP/COMPENSATION Feedback Loop Types In a typical LTC3703 circuit, the feedback loop consists of the modulator, the external inductor, the output capacitor and the feedback amplifier with its compensation network. All of these components affect loop behavior and must be accounted for in the loop compensation ...
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... So far, the AC response of the loop is pretty well out of the user’s control. The modulator is a fundamental piece of the LTC3703 design and the external L and C are usually chosen based on the regulation and load current require- ments without considering the AC loop response. The feedback amplifier, on the other hand, gives us a handle with which to adjust the AC response ...
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... To measure the modulator gain and phase directly, wire up a breadboard with an LTC3703 and the actual MOSFETs, inductor and input and output capacitors that the final design will use. This breadboard ...
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... V OUT REF Boost Converter Design The following sections discuss the use of the LTC3703 as a step-up (boost) converter. In boost mode, the LTC3703 can step-up output voltages as high as 80V. These sec- tions discuss only the design steps specific to a boost converter. For the design steps common to both a buck ...
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... MAX input of the converter and solid tantalum capacitors can fail catastrophically under these conditions. Be sure to specify surge-tested capacitors! Boost Converter: Current Limit Programming The LTC3703 provides current limiting in boost mode by RINGING DUE TO monitoring the V TOTAL INDUCTANCE (BOARD + CAP) and comparing it to the voltage at I ...
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... Soft-start reduces the input supply’s surge current by gradually increasing the duty cycle and can also be used for power supply sequencing. Pulling RUN/SS below 1V puts the LTC3703 into a low quiescent current shutdown (I driven directly from logic as shown in Figure 17. Releasing the RUN/SS pin allows an internal 4 A current source to ...
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... SS V SEC MIN ( where R1 and R2 are shown in Figure 10c. If the LTC3703 is operating in Pulse Skip Mode and the RUN/SS auxiliary output voltage drops below V SYNC pin will trip and the LTC3703 will resume continu ous operation regardless of the load on the main output. ...
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... Minimum on-time t is the smallest amount of time ON(MIN) that the LTC3703 is capable of turning the top MOSFET on and off again determined by internal timing delays and the amount of gate charge required to turn on the top MOSFET. Low duty cycle applications may approach this ...
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... Optimizing Loop Compensation Loop compensation has a fundamental impact on tran- sient recovery time, the time it takes the LTC3703 to recover after the output voltage has dropped due to a load step. Optimizing loop compensation entails maintaining the highest possible loop bandwidth while ensuring loop stability ...
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... LTC3703 circuits. Solder the MOSFET and the resistor(s) as close to the output of the LTC3703 circuit as possible and set up the signal generator to pulse at a 100Hz rate with a 5% duty cycle. This pulses the LTC3703 with 500 s transients10ms ...
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... Place the divider resistors near the LTC3703 in order to keep the high impedance FB node short and connect the source of the bottom side IN ...
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... For applications with multiple switching power convert- ers connected to the same input supply, make sure that the input filter capacitor for the LTC3703 is not shared with other converters. AC input current from another converter could cause substantial input voltage ripple, and this could ...
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... DRV RUN/ DRVCC GND BGRTN C VCC 1 F FZT600 + 22 F 25V 1 16 MODE/SYNC V IN 25k 2 15 FSET BOOST LTC3703 3 14 COMP 20k MAX INV DRV RUN/ DRVCC ...
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... DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE ** DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE LTC3703 .189 – .196* (4.801 – 4.978) .009 (0.229 REF .150 – ...
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... McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com 5V to 12V/5A Synchronous Boost Converter V CC 9.3V TO 15V + CMDSH-3 25V 1 16 MODE/SYNC FSET BOOST LTC3703 3 14 COMP 0 MAX INV ...