Ordering number : EN8273A LA5771MP Monolithic Linear IC Separately-excited Step-down Switching Regulator (3.3V) http://onsemi.com Overview The LA5771MP is a separately-excited step-down switching regulator (3.3V). Features • High efficiency • Four external parts • Time-base generator (160kHz) incorporated • Current limiter incorporated • Thermal shutdown circuit incorporated • Soft start circuit incorporated Specifications Absolute Maximum Ratings at Ta = 25°C Parameter Symbol Conditions Ratings Unit Input voltage VIN max 30 Output current IO max SW pin application reverse voltage Vsw Allowable power dissipation Pd max 3.9 W Operating temperature Topr -30 to +125 °C Storage temperature Tstg -40 to +150 °C Mounted on the specified board * V 3 A -1 V * Mounted on a specified board: 114.3mm×76.1mm×1.6mm, 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 5.5 to 28 Unit V 13107 MS IM B8-8794 No.8273-1/5 LA5771MP Electrical Characteristics at Ta = 25°C Parameter Symbol Ratings Conditions min Output voltage VO VIN=15V, IO=1.0A Efficiency η VIN=15V, IO=1.0A Unit typ 3.17 max 3.30 3.43 V 79 128 % Switching frequency f VIN=15V, IO=1.0A 160 192 kHz Line regulation ΔVOLINE VIN=8 to 20V, IO=1.0A 25 80 mV Load regulation ΔVOLOAD VIN=15V, IO=0.5 to 1.5A 10 30 mV Output voltage temperature coefficient ΔVO/ΔTa Designeed target value* Ripple attenuation factor RREJ F=100 to 120Hz Current limiter operating voltage IS VIN=15V ±0.5 mV/°C 45 dB 3.1 A Thermal shutdown operating temperature TSD Designed target value* 165 °C Thermal shutdown hysteresis width ΔTSD Designed target value* 15 °C * Designed target value: No measurement made. Package Dimensions unit : mm (typ) 3275 Pd max - Ta 4.5 1.5 9.9 1.3 4.5 (8.8) 1.2 10.0 (1.6) 0.9 1.7 0.2 0.4 1 5 2.7 SANYO : SMP5 Allowable power dissipation, Pd max - W 4.5 Mounted on a specified board: 114.3mm×76.1mm×1.6mm, Copper foil ratio 60% FR4 4.0 3.90 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -30 0 20 40 60 80 100 120 Ambient temperature, Ta - °C 140 160 ILA07131 Pin Assignment cVIN dSWOUT eGND fVOS gSS No.8273-2/5 LA5771MP Block Diagram VIN 1 2 SWOUT Reg. + - OSC OCP Reset Drive Comp. TSD 4 VOS Amp. VREF 3 GND 5 SS Application Circuit Example L1 SWOUT VIN LA5771MP C1 D1 VOS SS GND C2 C1: 220μF/35V C2: 1000μF/6.3V C3: 1μF/50V D1: SBD L1: 68μH C3 Notes: C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft function is not necessary. No.8273-3/5 LA5771MP Description of Functional Settings 1.Start delay function The SS pin has the internally-connected 22μA (typ) constant-current supply. When the voltage of SS pin exceeds the threshold voltage, the regulator starts operation. As the threshold is 0.62V(typ), the start delay time can be calculated as follows: ex. For setting at 1μF C × V 1μΑ × 0.62V = Td = = 28.2ms i 22μΑ 2.Soft start function The internal PWM waveform has the voltage value as shown in the right. If down-conversion from the voltage of VIN=15V to 3.3V output is to be made, for example, the PWM-ON duty has the value as shown below. 1.5V 0.62V PWM wave PWMduty = VOUT = 23% VIN - Vsat + VF (Note that calculation is made with Vsat=1V and VF=0.2V) The output voltage of error amplifier, which is 3.3V, is the value with PWM=23%, as calculated in the above equation, so that this voltage is determined as follows: Ver=(ΔVPWM)×PWMduty+VPWML=0.88V×0.23+0.62V=0.82V (ΔVPWM is the PWM amplitude value or 0.88V(typ) while VPWML is the lower limit voltage of PWM waveform or 0.62V(typ)) SS pin and error amplifier output voltages are designed to prefer the lower voltages, so that VOUT will reach the designed regulation voltage in timing when the SS pin voltage exceeds the error amplifier output. Therefore, the soft strt time is calculated as follows: Tss = C × ΔVPWM × PWMduty C × 0.88V × PWMduty = i 22μA For the set conditions of C=1μF and PWMduty=23%: Tss = 1μΑ × 0.88V × 0.23 = 9.2ms 22μA No.8273-4/5 LA5771MP Timing Chart VIN SWOUT VOUT Td Tss 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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