Ordering number : ENA0476A LA5779 Monolithic Linear IC Separately-excited Step-down Switching Regulator (Variable Type) http://onsemi.com Overview The LA5779 is a Separately-excited step-down switching regulator (variable type). Functions • High efficiency. • Six external parts. • Time-base generator (160kHz) incorporated. • Current limiter incorporated. • Thermal shutdown circuit incorporated. • ON/OFF function. Specifications Absolute Maximum Ratings at Ta = 25°C Parameter Symbol Maximum Input voltage VIN max 30 V IO max 3 A VSW -1 V 7.5 W Maximum Output current SW pin application reverse voltage Allowable power dissipation Conditions Pd max1 Infinitely large heat sink. Pd max2 Independent IC. Ratings Unit 1.75 W Operating temperature Topr -30 to +125 °C Storage temperature Tstg -40 to +150 °C Junction temperature Tj max 150 °C Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. Recommended Operating Conditions at Ta = 25°C Parameter Input voltage range Symbol VIN Semiconductor Components Industries, LLC, 2013 August, 2013 Conditions Ratings Unit 4.5 to 28 V 62707 MS PC 20070619-S00001 / N1306 MS PC 20060606-S00001 No.A0476-1/4 LA5779 Electrical Characteristics at Ta = 25°C, VO = 3.3V Parameter Symbol Ratings Conditions min Reference voltage VOS 1.20 max 1.23 1.26 V η VIN = 15V, IO = 1.0A, Set VO = 5V f VIN = 15V, IO = 1.0A 128 160 192 kHz fshort VIN = 15V, VOS = 0V 15 30 45 kHz 40 100 mV 10 30 Efficiency Switching frequency Switching frequency when VIN = 15V, IO = 1.0A Unit typ 84 % short-circuit protection is active Line regulation ΔVOLINE VIN = 8 to 20V, IO = 1.0A Load regulation ΔVOLOAD VIN = 15V, IO = 0.5 to 1.5A ΔVO/ΔTa Output voltage temperature ±0.5 Designed target value. * mV mV/°C coefficient Ripple attenuation factor RREJ f = 100 to 120Hz Output leak current IOleak VIN = 15V, SWOUT = -0.4V Current limiter operating voltage IS Operating current 45 VIN = 15V IVIN dB μA 50 3.1 A VIN = 15V 5.6 mA VIN = 15V, ENA = 5V 200 μA 0.6 V Standby current ISTBY ENA pin LOW voltage range VENAL ENA pin HIGH voltage range VENAH Thermal shutdown operating TSD Designed target value. * 165 °C ΔTSD Designed target value. * 15 °C 2.4 VIN V temperature Thermal shutdown Hysteresis width * Design target value: No measurement made. Package Dimensions unit : mm (typ) 3079A Pd max -- Ta 4.5 2.7 10.4max 10.0 2.7 0.9 5 1 0.8 (1.6) 17.8 21.3 23.0 15.0 1.3 (8.8) 3.6 Allowable pwer dissipation, Pd max -- W 10.0 1.7 0.45 4.5 8.0 7.5 100×100×1.5mm3 6.0 5.6 50×50×1.5mm3 4.0 3.3 2.0 1.75 Al heat sink plate tightening torque 39N.cm With silicone grease applied. 30×30×1.5mm3 No heat sink 0 --30 8.4 Infinitely large heat sink θjc=5°C/W 0 20 40 60 80 100 120 Ambient temperature, Ta -- °C 140 160 PCA00833 SANYO : TO-220-5H Pin Assignment (1) VIN (2) SWOUT (3) GND (4) VOS (5) ENA No.A0476-2/4 LA5779 Block Diagram VIN 1 2 SWOUT Reg. OCP Reset OSC Drive Comp. THD 4 VOS Amp. VREF 5 3 ENA GND Application Circuit Example L1 47μH VIN SWOUT LA5779 C2 390μF D1 SBD C1 470μF /50V VOS ENA GND R2 R1 No.A0476-3/4 LA5779 Description of Functional Settings Calculation equation to set the output voltage This IC controls the switching output so that the VOS pin voltage becomes 1.23V (typ). The equation to set the output voltage is as follows: R2 VO = 1+ × 1.23V(typ) R1 The VOS pin has the inrush current of 1μA (typ). Therefore, the error becomes larger when R1 and R2 resistance values are large. ON Semiconductor and the ON logo are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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This literature is subject to all applicable copyright laws and is not for resale in any manner. PS No.A0476-4/4