Ordering number : ENA0717C LA5744 Monolithic Linear IC Separately-Excited Step-Down Switching Regulator (Variable Type) http://onsemi.com Overview The LA5744 is a separately-excited step-down switching regulator (variable type). Functions • High efficiency. • Time-base generator (300kHz) incorporated. • Current limiter incorporated. • Thermal shutdown circuit incorporated. • Soft start circuit incorporated. Specifications Maximum Ratings at Ta = 25°C Parameter Input voltage Maximum output current SW pin application reverse voltage Allowable power dissipation Symbol Conditions Ratings Unit VIN 30 IO max 3 A VSW -1 V 1.75 W Pd max1 No heat sink Pd max2 Infinite heat sink V 7.5 W Topr -30 to +125 °C Storage temperature Tstg -40 to +150 °C Junction temperature Tj max 150 °C Operating temperature * Specified circuit board : 76.1×114.3×1.6mm3 : Copper foil ratio 60% FR4 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 52307 MS PC 20070522-S00004 / 42507 MS PC / 31407 MS PC / 30707 MS PC No.A0717-1/5 LA5744 Electrical Characteristics at Ta = 25°C, VO = 5V Parameter Symbol Ratings Conditions min Reference voltage VOS VIN = 15V, IO = 1.0A η VIN = 15V, IO = 1.0A Efficiency Switching frequency f typ 1.20 Unit max 1.23 1.26 V 83 VIN = 15V, IO = 1.0A 300 360 kHz Line regulation ΔVOLINE VIN = 8 to 20V, IO = 1.0A 40 100 mV Load regulation ΔVOLOAD VIN = 20V, IO = 0.5 to 1.5A 10 30 ΔVO/ΔTa Output voltage temperature 240 % ±0.5 Designed target value. * mV mV/°C coefficient Ripple attenuation factor RREJ Current limiter operating voltage f = 100 to 120Hz IS Thermal shutdown operating 45 VIN = 15V dB 3.1 A TSD Designed target value. * 165 °C ΔTSD Designed target value. * 15 °C temperature Thermal shutdown Hysteresis width * Design target value : No measurement made. Package Dimensions unit : mm (typ) 3343 Pd max -- Ta 4.5 10.4MAX 10.0 1.3 21.7 23.0 15.3 (8.8) 15.0 2.7 3.6 0.9 2.7 1 0.8 (1.6) 8.0 7.5 100×100×1.5mm3 6.0 5.6 50×50×1.5mm3 4.0 3.3 2.0 1.75 1.7 0.4 4.5 Infinite heat sink θjc=5°C Al heat sink mounting torque 39N⋅cm silicone grease applied 30×30×1.5mm3 No heat sink 0 -30 -20 5 2 Allowable power dissipation, Pd max -- W 10.0 0 20 40 60 80 100 Ambient temperature, Ta -- °C 120 140 160 MSG07021 8.4 SANYO : 220-5HK Pin Assignment (1) VIN (2) SWOUT (3) GND (4) VOS (5) SS No.A0717-2/5 LA5744 Block Diagram VIN 1 2 SWOUT Constant current circuit Reg. OCP Reset OSC Drive Comp. TSD 4 VOS Amp. ON/OFF Comp. 0.4V VREF 5 3 SS GND Application Circuit Example L1 22μH VIN SWOUT LA5744 C2 390μF D1 SBD C1 470μF /50V VOS SS GND R2 R1 C3 1μF Notes : 1. C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft start function is not necessary. 2. In some cases, the output may not turn on if power is applied when a load is connected. If this is a problem, increase the value of the inductor. No.A0717-3/5 LA5744 Protection Circuit Functional Descriptions 1. Overcurrent protection function The overcurrent protection function detects, on a cycle-by-cycle basis, the output transistor current and turns off that output transistor current if it exceeds 3.1A. Limit current Inductor current SWOUT voltage 2. Short circuit protection function This IC prevents the current from increasing when the outputs are shorted by setting the switching frequency to 30kHz if the VOS pin voltage falls below 0.8V. Note 3 : If the soft start function is not used, the IC will start up with the overcurrent protection function operating. At this time, the switching frequency will be cut in half. This means that the switching frequency will be 15kHz at startup. Note 4 : Since the switching frequency becomes 30kHz when the VOS pin voltage falls under 0.8V, the current capacity is reduced. If a load is applied with the VOS pin voltage over 0.8V, the inductance value operates at 22μH. If a load is to be applied when this voltage is under 0.8V, the inductance value must be increased. Description of Functional Settings 1. 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. 2. Startup Delay Function The output voltage rises when the internal voltage reaches 0.4V (typical). Until that point, a capacitor is charged from an internal 10μA (typical) constant-current supply. The startup delay time can be calculated as shown below Example : Assume a 1μF capacitor is used. Td = C × V 1μF × 0.4 = = 40 ms i 10μA No.A0717-4/5 LA5744 Timing Chart VIN voltage 30kHz 300kHz SWOUT voltage 1.23V 0.8V VOS voltage 0V Td 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. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner. PS No.A0717-5/5