L4971 1.5A STEP DOWN SWITCHING REGULATOR UP TO 1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 3.3V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO 50V SWITCHING FREQUENCY ADJUSTABLE UP TO 500KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE-BYPULSE AND HICCUP MODE) INHIBIT FOR ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION DESCRIPTION The L4971 is a step down monolithic power switching regulator delivering 1.5A at a voltage between 3.3V and 50V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdson of 0.25Ω) to obtain very high efficency and high switching speed. Minidip SO16W ORDERING NUMBERS: L4971 (Minidip) L4971D (SO16) A switching frequency up to 500KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 50V cover the majority of today’s applications. Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16W for SMD assembly. TYPICAL APPLICATION CIRCUIT Vi=8V to 55V 5 8 R1 20K L4971 3 C1 220µF 63V C7 220nF C2 2.7nF C5 100nF 2 4 7 1 R2 9.1K C4 22nF L1 126µH (77120) 6 C6 100nF D1 GI SB360 VO=3.3V/1.5A C8 330µF D97IN748A May 2000 1/12 L4971 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH 2 INHIBIT SOFTSTART 3.3V COMP FB INTERNAL REFERENCE INTERNAL SUPPLY 5.1V 7 6 E/A 8 PWM 3.3V R Q S CBOOT CHARGE AT LIGHT LOADS DRIVE OSCILLATOR 1 3 OSC BOOT 4 GND OUT D97IN594 PIN CONNECTIONS GND 1 8 FB SS_INH 2 7 COMP OSC 3 6 BOOT OUT 4 5 VCC N.C. 1 16 N.C. GND 2 15 N.C. SS_INH 3 14 FB OSC 4 13 COMP OUT 5 12 BOOT OUT 6 11 VCC N.C. 7 10 N.C. N.C. 8 9 N.C. D97IN595 D97IN596 Minidip SO16W PIN FUNCTIONS DIP 1 2 SO (*) 2 3 Name GND SS_INH 3 4 OSC 4 5 6 5, 6 11 12 OUT VCC BOOT 7 8 13 14 COMP FB Function Ground A logic signal (active low) disables the device (sleep mode operation). A capacitor connected between this pin and ground determines the soft start time. When this pin is grounded disables the device (driven by open collector/drain). An external resistor connected between the unregulated input voltage and this pin and a capacitor connected from this pin to ground fix the switching frequency. (Line feed forward is automatically obtained) Stepdown regulator output Unregulated DC input voltage A capacitor connected between this pin and OUT allows to drive the internal DMOS Transistor E/A output to be used for frequency compensation Stepdown feedback input. Connecting directly to this pin results in an output voltage of 3.3V. An external resistive divider is required for higher output voltages. (*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 2/12 L4971 THERMAL DATA Symbol Parameter Thermal Resistance Junction to ambient R th(j-amb) Max. Minidip SO16 Unit 90 (*) 110 (*) °C/W (*) Package mounted on board. ABSOLUTE MAXIMUM RATINGS Symbol Minidip S016 V5 V11 V4 V5,V6 Parameter Value Unit Input voltage 58 V Output DC voltage Output peak voltage at t = 0.1µs f=200KHz -1 -5 V V I4 I5,I6 V6-V5 V12-V11 V6 V12 Bootstrap voltage 70 V V7 V13 Analogs input voltage (VCC = 24V) 12 V V2 V3 Analogs input voltage (VCC = 24V) 13 V V8 V14 (VCC = 20V) 6 -0.3 V V Minidip 1 W SO16 0.8 W -40 to 150 °C Ptot Tj,Tstg Maximum output current int. limit. 14 Power dissipation a Tamb ≤ 60°C Junction and storage temperature V ELECTRICAL CHARACTERISTICS (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ, VCC = 24V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125°C Symbol Parameter Test Condition Min. Typ. Max. Unit 55 3.39 3.427 3.5 0.55 0.88 3 V V V V V V A % KHz dB DYNAMIC CHARACTERISTIC VI Vo Vd Il fs SVRR Operating input voltage range Output voltage Dropout voltage Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency Vo = 3.3 to 50V; Io = 1.5A Io = 0.5A Io = 0.2 to 1.5A Vcc = 8 to 55V Vcc = 10V; Io = 1.5A Vcc = 8 to 55V Vo = 3.3V; Io = 1.5A * * 8 3.33 3.292 3.22 * * 2 * Vi = Vcc+2VRMS; Vo = Vref; Io = 1.5A; f ripple = 100Hz Vcc = 8 to 55V 90 60 3.36 3.36 3.36 0.44 2.5 85 100 3 Tj = 0 to 125°C 110 6 4 % % Soft Start Soft start charge current Soft start discharge current 30 6 40 10 50 14 µA µA 5 0.9 15 V µA Inhibit VLL IsLL Low level voltage Isource Low level * * 3/12 L4971 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Test Condition Min. Typ. Max. Unit 4 6 mA 2.5 100 150 3.5 200 300 mA µA µA 3.36 5 0.4 3.39 10 V mV mV/°C DC Characteristics Iqop Iq Iqst-by Total operating quiescent current Quiescent current Total stand-by quiescent current Duty Cycle = 0; VFB = 3.8V Vinh <0.9V Vcc = 55V; Vinh <0.9V Error Amplifier VFB RL VoH VoL Io source Io sink Ib SVRR E/A gm Voltage Feedback Input Line regulation Ref. voltage stability vs temperature High level output voltage Low level output voltage Source output current Sink output current Source bias current Supply voltage ripple rejection DC open loop gain Transconductance 3.33 Vcc = 8 to 55V * VFB = 2.5V VFB = 3.8V Vcomp = 6V; V FB = 2.5V Vcomp = 6V; V FB = 3.8V Vcomp = Vfb; Vcc = 8 to 55V RL = ∞ Icomp = -0.1 to 0.1mA Vcomp = 6V 10.3 0.65 200 200 60 50 300 300 2 80 57 2.5 3 V V µA µA µA dB dB ms Oscillator Section Ramp Valley Ramp peak Maximum duty cycle Maximum Frequency 4/12 Vcc = 8V Vcc = 55V Duty Cycle = 0% Rosc = 13kΩ, Cosc = 820pF 0.78 2 9 95 0.85 2.15 9.6 97 0.92 2.3 10.2 500 V V V % kHz L4971 Typical Performance (Using Evaluation Board) fsw = 100kHz Output Voltage Output Ripple Efficiency VCC =35V IO = 1.5A Line Regulation Io = 1.5A VCC = 8 to 55V Load Regulation VCC =35V IO = 0.5 to 1.5A 3.3V 10mV 84 (%) 3mV 6mV 5.1V 10mV 86 (%) 3mV 6mV 12V 12mV 93 (%) 3mV (VCC =15 to 55V) 4mV Figure 1. Test and valuation board circuit. Vi=8V to 55V 5 8 R1 20K L4971 3 C1 220µF 63V C7 220nF C2 2.7nF 7 2 C5 100nF VO=3.3V/1.5A 4 1 R2 9.1K L1 126µH (77120) 6 C6 100nF C4 22nF D1 GI SB360 R3 C8 330µF R4 D97IN749A C1=220µF/63V EKE C2=2.7nF C5=100nF C6=100nF C7=220nF/63V C8=330µF/35V CG Sanyo L1=126µH KoolMu 77120 - 65 Turns - 0.5mm R1=20K R2=9.1K D1=GI SB360 L4971 VO(V) R3(KΩ) 3.3 0 R4(KΩ) 5.1 2.7 4.7 12 12 4.7 15 16 4.7 18 20 4.7 24 30 4.7 Figure 2. PCB and component layout of the figure 1. 5/12 L4971 Figure 3. Quiescent drain current vs. input voltage. Iq (mA) D97IN724 200KHz R 1=22K C 2=1.2nF 5 Figure 4. Quiescent current vs. junction temperature D97IN731 Iq (mA) 200KHz R1=22K C2=1.2nF 5 4 100KHz R 1=20K C 2=2.7nF 4 3 0Hz 3 100KHz R1 =20K C2 =2.7nF 0Hz VCC=35V 0% DC 2 2 Tamb=25°C 0% DC 1 1 0 5 10 15 20 25 30 35 40 45 50 Figure 5. Stand-by drain current vs. input voltage Ibias (µA) D97IN732 VO (V) D97IN733 Tj=125°C Tj=25°C 140 Figure 6. Line Regulation 3.377 Vss=GND 150 -50 -30 -10 10 30 50 70 90 110 Tj(°C) Vcc(V) 3.376 130 3.375 120 Tj=25°C 3.374 110 3.373 Tj=125°C 100 90 3.372 80 3.371 70 60 3.370 0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 8. Switching frquency vs. R1 and C2 Figure 7. Load regulation VO (V) 3.378 5 10 15 20 25 30 35 40 45 50 VCC(V) D97IN734 V CC=35V fsw (KHz) D97IN784 500 Tamb=25°C 3.376 0.8 2nF 200 3.374 Tj=25°C 3.372 1.2 nF 100 3.370 2.2 nF Tj=125°C 50 3.368 3.3n F 3.366 4.7n F 20 5.6n 3.364 F 10 3.362 3.360 5 0 6/12 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 0 20 40 60 80 R1(KΩ) L4971 Figure 9. Switching Frequency vs. input voltage. fsw (KHz) D97IN735 Figure 10. Switching frequency vs. junction temperature. fsw (KHz) D97IN785 107.5 105.0 105 102.5 Tj=25°C 100.0 100 97.5 95.0 95 92.5 90.0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 11. Dropout voltage between pin 5 and 4. ∆V (V) D97IN736 Tj=125°C 0.5 90 -50 0 50 C 5° =2 Tj Tj(°C) Figure 12. Efficiency vs output voltage. η (%) D97IN737 100KHz 96 94 0.4 100 200KHz 92 90 0.3 Tj=-25°C 0.2 VCC=35V IO=1.5A 88 86 0.1 84 82 0.0 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 13. Efficiencyvs. output current. η (%) D97IN738 VCC=8V VCC=12V 90 15 η (%) 20 25 VO(V) D97IN739 VCC=8V 85 VCC =12V VCC=24V VCC=24V 80 80 70 10 Figure 14. Efficiencyvs. output current. 90 85 75 5 VCC=48V VCC=48V 75 fsw=100KHz VO=5.1V 70 65 65 60 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 60 fsw=100KHz VO=3.36V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 7/12 L4971 Figure 15. Efficiencyvs. output current. D97IN740 η (%) V CC=8V 90 η (%) D97IN741 VCC=8V 90 VCC=12V 85 VCC=24V 85 Figure 16. Efficiencyvs. output current. VCC=12V 80 80 VCC=48V VCC=24V 75 75 70 VCC=48V 70 fsw=200KHz VO=5.1V 65 60 65 fsw=200KHz VO=3.36V 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 17. Efficiencyvs. Vcc. 55 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 18. Power dissipation vs. Vcc. η (%) D97IN742 Pdiss (mW) D97IN743 V0 =5 .1V-f SW =1 V0 = 85 VO=5.1V fsw=100KHz 00KH z 800 5.1 V-f SW = 20 V0 = 0K Hz 80 IO=1A V-f SW = V 0 =3 .36 100 KHz V- fS W= 400 IO=0.5A 12 0 0K 75 70 IO=1.5A 600 3.36 Hz IO=1.5A 0 10 20 30 40 200 50 VCC(V) 0 0 10 20 30 40 50 VCC(V) Figure 20. Pulse by pulse limiting current vs. junction temperature. Figure 19. Efficiencyvs. Vo. Pdiss (mW) D97IN744 VCC=35V fsw=100KHz Ilim (A) D97IN747 fsw=100KHz VCC=35V 2.9 800 2.8 IO=1.5A 600 2.7 IO=1A 400 IO=0.5A 2.6 2.5 200 2.4 0 8/12 0 5 10 15 20 25 30 V0(V) 2.3 -50 -25 0 25 50 75 100 125 Tj(°C) L4971 Figure 22. Line transient. Figure 21. Load transient. VCC (V) D97IN786 30 20 10 VO (mV) 1 IO = 1A fsw = 100KHz 100 2 0 -100 1ms/DIV Figure 23. Soft start capacitor selection Vs inductor and Vccmax. L (µH) D97IN745 L (µH) Figure 24. Soft start capacitor selection vs. Inductor and Vccmax. 680nF D97IN746 fsw=200KHz 470nF fsw=100KHz 400 56nF 300 47nF 200 33nF 330nF 300 220nF 200 22nF 100 100 100nF 0 15 20 25 30 35 40 45 50 VCCmax(V) 0 15 20 25 30 35 40 45 50 VCCmax(V) Figure 25. Open loop frequency and phase of error amplifier GAIN (dB) D97IN787 Phase 50 GAIN 0 0 -50 45 90 -100 Phase 135 -150 -200 10 10 2 103 104 105 106 10 7 108 f(Hz) 9/12 L4971 mm DIM. MIN. A TYP. inch MAX. MIN. 3.32 TYP. MAX. 0.131 a1 0.51 B 1.15 1.65 0.045 0.065 b 0.356 0.55 0.014 0.022 b1 0.204 0.304 0.008 0.012 0.020 D E 10.92 7.95 9.75 0.430 0.313 0.384 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 F 6.6 0.260 I 5.08 0.200 L Z 10/12 3.18 OUTLINE AND MECHANICAL DATA 3.81 1.52 0.125 0.150 0.060 Minidip L4971 mm DIM. MIN. TYP. inch MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.1 0.3 0.004 0.012 B 0.33 0.51 0.013 0.020 C 0.23 0.32 0.009 0.013 D 10.1 10.5 0.398 0.413 E 7.4 7.6 0.291 0.299 e 1.27 0.050 H 10 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 L 0.4 1.27 0.016 0.050 K OUTLINE AND MECHANICAL DATA SO16 Wide 0° (min.)8° (max.) L h x 45 A B e K A1 C H D 16 9 E 1 8 11/12 L4971 Information furnished is believed to be accurate and reliable. However, STMicroelectroni cs assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. 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