LTC1702ACGN#TR-SMI Linear Technology, LTC1702ACGN#TR-SMI Datasheet

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... Distributed Power Applications ■ High Efficiency Power Conversion , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6144194. U TYPICAL APPLICATIO ...

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LTC1702A ABSOLUTE MAXIMUM (Note 1) Supply Voltage V CC ........................................................................................... BOOST n ............................................................... 15V BOOST n – .................................................... 7V Input Voltage SW n .......................................................... – All Other Inputs ......................... – 0.3V to ...

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ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are 25° unless otherwise specified. (Note 3) CC SYMBOL PARAMETER V FCB Threshold FCB ∆V FCB Feedback Hysteresis ...

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LTC1702A W U TYPICAL PERFOR A CE CHARACTERISTICS Efficiency vs Load Current 100 3.3V OUT V = 2.5V OUT 1.6V OUT LOAD CURRENT (A) 1702A ...

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PIN FUNCTIONS PV (Pin 1): Driver Power Supply Input power to the two BG n output drivers. PV connected to a voltage high enough to fully turn on the external MOSFETs QB1 and QB2. PV ...

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LTC1702A PIN FUNCTIONS FB1 (Pin 12): Controller 1 Feedback Input. FB1 should be connected through a resistor network to V output voltage. The loop compensation network for con- troller 1 also connects to FB1. V (Pin 13): ...

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TEST CIRCUIT f OSC MEASURED 10k V PGOOD1 V FB1 U U APPLICATIONS INFORMATION OVERVIEW The LTC1702A is a dual, step-down (buck), voltage mode feedback switching regulator controller designed to be used in a synchronous ...

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LTC1702A U U APPLICATIONS INFORMATION 2-Step Conversion “2-step” architectures use a primary regulator to convert the input power source (batteries or AC line voltage intermediate supply voltage, often 5V. This intermediate voltage is then converted to the low ...

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U U APPLICATIONS INFORMATION remember that the power losses are proportional to I meaning that the actual power wasted is reduced by a factor of 3.75. The reduced input ripple voltage also means less power is lost in the input ...

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LTC1702A U U APPLICATIONS INFORMATION amp of continuous current with peak currents slew large MOSFET gates quickly. The external MOSFETs are connected with the drain of QT attached to the input supply and the source of ...

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U U APPLICATIONS INFORMATION Feedback Amplifier Each side of the LTC1702A senses the output voltage at V with an internal feedback op amp (see Block Dia- OUT gram). This is a real op amp with a low impedance output, 85dB ...

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LTC1702A U U APPLICATIONS INFORMATION SHUTDOWN/SOFT-START Each half of the LTC1702A has a RUN/SS pin. The RUN/SS pins perform two functions: when pulled to ground, each shuts down its half of the LTC1702A, and each acts as a conventional soft-start ...

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U U APPLICATIONS INFORMATION Any time and the current flowing to the output is reasonably large, the SW node at the drain of QB will be somewhat negative with respect to PGND. The LTC1702A senses this voltage ...

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LTC1702A U U APPLICATIONS INFORMATION LTC1702A remains in continuous mode. See the Inductor Selection section for a detailed description of ripple current. As the output load current decreases in continuous mode, the average current in the inductor will reach a ...

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U U APPLICATIONS INFORMATION Burst Mode Operation Discontinuous mode removes the resistive loss drop term in QB, but the LTC1702A is still switching QT and QB on and off once a cycle. Each time an external MOSFET is turned on, ...

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LTC1702A U U APPLICATIONS INFORMATION remains in this state until both RUN/SS pins are pulled low simultaneously, the power supply is recycled, or the FAULT pin is pulled low externally. This behavior is in- tended to protect a potentially expensive ...

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U U APPLICATIONS INFORMATION where the charge is going, the fact remains that it all has to come out turn the MOSFET gate on, and when CC the MOSFET is turned back off, that charge all ends ...

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LTC1702A U U APPLICATIONS INFORMATION implies a duty cycle of 32%, which means 32% of each switching cycle. During QT’s on-time, the current drawn from the input equals the load current and during the rest of the ...

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U U APPLICATIONS INFORMATION from C (time point A). 50% of the way through, TG2 IN turns on and the total current is 13A (time point B). Shortly thereafter, TG1 turns off and the current drops to 10A (time point ...

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LTC1702A U U APPLICATIONS INFORMATION 32% 10A 68% 0 32% 6.8A 68% 0 –3.2A 32% 18% 32% 18% 10A 0 32% 18% 32% 18% 3.6A 0 –6.4A Figure 7. RMS Input Current current that the LTC1702A will draw. If the ...

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U U APPLICATIONS INFORMATION output, with the attendant 180° phase shift. This roll-off is what filters the PWM waveform, resulting in the desired DC output voltage, but the phase shift complicates the loop compensation if the gain is still higher ...

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LTC1702A U U APPLICATIONS INFORMATION Type 2 loops work well in systems where the ESR zero in the LC roll-off happens close to the LC pole, limiting the total phase shift due to the LC. The additional phase compensation in ...

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... OUT V(OUT) in degrees. Refer to your SPICE manual for details of how to generate this plot. *1702A modulator gain/phase © * 2001 Linear Technology *this file written to run with PSpice 8.0 *may require modifications for other SPICE simulators *MOSFETs rfet mod sw 0.02 ;MOSFET rdson ...

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LTC1702A U U APPLICATIONS INFORMATION Type 3 Loop: ⎛ ⎞ BOOST = + ° Tan 45 ⎜ ⎟ ⎝ ⎠ πƒ – ...

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U U APPLICATIONS INFORMATION LTC1702A QB BG FCB Figure 13. Regulating an Auxiliary Output with the FCB Pin be added, either unregulated or with additional external circuitry at the FCB pin. The extra ...

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LTC1702A U U APPLICATIONS INFORMATION OPTIMIZING PERFORMANCE 2-Step Conversion The LTC1702A is ideally suited for use in 2-step conver- sion systems. 2-step systems use a primary regulator to convert the input power source (batteries or AC line voltage ...

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U U APPLICATIONS INFORMATION 2-Step Efficiency Calculation Calculating the efficiency of a 2-step converter system involves some subtleties. Simply multiplying the effi- ciency of the primary 5V or 3.3V supply by the efficiency of the 1.8V or 1.5V supply underestimates ...

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LTC1702A U U APPLICATIONS INFORMATION Maximizing Low Load Current Efficiency Low load current efficiency depends strongly on proper operation in discontinuous and Burst Mode operations ideally optimized system, discontinuous mode reduces conduction losses but not switching losses, since ...

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U U APPLICATIONS INFORMATION cycles. Over just a few cycles, however, the external components conspire to limit the speed that the output can move. Consider our typical 5V to 1.6V circuit, sub- jected load transient. ...

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LTC1702A U U APPLICATIONS INFORMATION Making L smaller than this optimum value yields little or no improvement in transient response. As the output voltage recovers, the inductor current will briefly rise above the level of the output current to replenish ...

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U U APPLICATIONS INFORMATION it goes out of spec. Similarly, at full load, the output current can only decrease, causing a positive shift in the output voltage; the initial low value allows it to rise further before the spec is ...

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LTC1702A U U APPLICATIONS INFORMATION FAULT BEHAVIOR Changing the Output Voltage on the Fly Some applications use a switching scheme attached to the feedback resistors to allow the system to adjust the LTC1702A output voltage. The voltage can be changed ...

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U TYPICAL APPLICATIONS LTC1702A 1702afa 33 ...

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LTC1702A U TYPICAL APPLICATIONS 34 1702afa ...

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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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...

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... V LTC1876 , High Power, 2-Phase, Dual Output, Synchronous IN Step-Down Controller LTC1929 2-Phase, Synchronous High Efficiency Converter trademark of Linear Technology Corporation. Pentium is a registered trademark of Intel Corporation. SENSE Linear Technology Corporation 36 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● ...