L5971 1.5A STEP DOWN SWITCHING REGULATOR UP TO 1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 6.5V TO 28V PRECISE 1.26V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 1.26V TO 20V 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 Minidip SO16W ORDERING NUMBERS: L5971 (Minidip) L5971D (SO16) A switching frequency up to 500KHz is achievable (the maximum power dissipation of the packages must be observed). 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 SO16 for SMD assembly. Typical Applications: - High efficiency step-down converter - Portable computers - Battery charger - Distributed power - PDAs and Mobile Comminicators DESCRIPTION The L5971 is a step down monolithic power switching regulator delivering 1.5A at a voltage between 1.26V and 20V (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. TYPICAL APPLICATION CIRCUIT Vi=6V to 28V 5(11) R1 22K 3(4) C1 47µF 30V 2(3) C2 1.2nF 8(14) L5971 7(13) VO=2.5V/1.5A 4(5,6) L1 30µH 1(2) 6(12) R3 C5 47nF R2 9.1K C4 22nF C6 100nF D1 STPS 3L40U C8 330µF R4 D98IN832C May 2000 1/11 L5971 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH 2 INHIBIT SOFTSTART 1.26V COMP FB INTERNAL REFERENCE INTERNAL SUPPLY 5.1V 7 6 E/A 8 PWM 1.26V R Q S CBOOT CHARGE AT LIGHT LOADS DRIVE OSCILLATOR 1 3 OSC BOOT 4 GND OUT D98IN833 PIN CONNECTIONS GND 1 8 FB SS_INH 2 7 COMP OSC 3 6 BOOT OUT 4 5 VCC D97IN595 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. D97IN596 Minidip SO16W PIN FUNCTIONS DIP 1 2 SO (*) 2 3 Name GND SS_INH 3 4 OSC 4 5 6 7 8 5, 6 11 12 13 14 OUT VCC BOOT 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 Not regulated DC input voltage A capacitor connected between this pin and OUT allows to drive the internal VDMOS E/A output to be used for frequency compensation Stepdown feedback input. Connecting directly this pin to the output 1.26V is obtained; a voltage divider is requested for higher output voltages (*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 2/11 L5971 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, V3 V11, V4 V4 V5,V6 Parameter I4 I5,I6 V6-V5 V12-V11 V6 V12 V7,V2 V13,V3 V8 V14 Ptot Tj,Tstg Value Unit Input voltage 30 V Output DC voltage Output peak voltage at t = 0.1µs f=200KHz -1 -5 V V Maximum output current int. limit. 14 V Bootstrap voltage 45 V Analogs input voltage (VCC = 12V) 10 V 6 -0.3 V V Minidip 1 W SO16 0.8 W -40 to 150 °C (VCC = 20V) Power dissipation a Tamb ≤ 60°C Junction and storage temperature ELECTRICAL CHARACTERISTICS (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ, VCC = 12V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125°C Symbol Parameter Test Condition Min. Typ. Max. Unit 28 1.273 1.285 1.31 0.55 0.88 3 V V V V V V A % KHz dB DYNAMIC CHARACTERISTIC VI Vo Operating input voltage range Output voltage Vd Dropout voltage Il fs SVRR Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency * Io = 0.5A Io = 0.2 to 1.5A Vcc = 6.5 to 25V Vcc = 10V; Io = 1.5A Vcc = 6.5 to 25V Vo = 3.3V; Io = 1.5A * 6.5 1.247 1.235 1.21 * * 2 * Vi = Vcc+2VRMS; Vo = Vref; Io = 1.5A; f ripple = 100Hz Vcc = 6.5 to 25V 90 60 1.26 1.26 1.26 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 * * 3/11 L5971 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Test Condition Min. Typ. Max. Unit 3 4.5 mA 2.8 100 150 3.5 200 300 mA µA µA 1.26 5 0.4 1.273 10 V mV mV/°C DC Characteristics Iqop Iq Iqst-by Total operating quiescent current Quiescent current Total stand-by quiescent current Pin 5 (Pin 11) Duty Cycle = 0; VFB = 1.7V Vinh <0.9V Vcc = 25V; 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 1.247 Vcc = 6.5 to 25V * VFB = 0.8V VFB = 1.7V Vcomp = 3V; V FB = 0.8V Vcomp = 3V; V FB = 1.7V Vcomp = Vfb; Vcc = 6.5 to 25V RL = ∞ Icomp = -0.1 to 0.1mA Vcomp = 6V 8.7 0.65 180 200 60 50 250 300 2 80 57 4.3 3 V V µA µA µA dB dB mS Oscillator Section Ramp Valley Ramp peak Maximum duty cycle Maximum Frequency 4/11 Vcc = 6.5V Vcc = 25V Duty Cycle = 0% Rosc = 13kΩ, Cosc = 820pF 0.74 1.80 4.72 95 0.81 1.87 4.79 97 0.88 1.94 4.86 500 V V V % kHz L5971 Figure 1. Test and valutation board circuit. Vi=6V to 28V 5(11) R1 22K 3(4) C1 47µF 30V 2(3) 8(14) L5971 VO (V) V O=2.5V/1.5A 4(5,6) L1 30µH 1(2) 6(12) 7(13) R3 C2 1.2nF C5 47nF R2 9.1K C4 22nF C6 100nF D1 STPS 3L40U C8 330µF R4 R3 (KΩ) R4 (KΩ) 1.8 1 2 1.5 0.5 2 2.5 2 2 3.3 8.2 4.7 5.1 12 3.6 12 27 3 15 23 2 D98IN832C Figure 2. PCB and component layout of the figure 1. SOLDER SIDE COMPONENT SIDE 5/11 L5971 Figure 3. Quiescent drain current vs. input voltage. Iq (mA) D98IN942 Figure 4. Quiescent current vs. junction temperature D98IN943 Iq (mA) VCC=20V 0% DC 5 5 200KHz R1=22K C2=1.2nF 4 4 200KHz; R1=22K; C2=1.2nF 100KHz; R =2 1 0K; C2=2.7nF 3 3 100KHz; R1=20K C2=2.7nF 0Hz 0Hz 2 2 Tamb=25°C 0% DC 1 1 0 5 10 15 20 25 Vcc(V) Figure 5. Stand-by drain current vs. input voltage Ibias (µA) D98IN944 -50 -30 -10 10 30 50 70 90 110 Tj(°C) Figure 6. Line Regulation VO (V) D98IN945 3.377 150 Vss=GND 140 3.376 130 3.375 Tj=125°C 120 3.374 110 Tj=25°C 3.373 100 90 Tj=25°C 3.372 Tj=125°C 80 3.371 70 60 3.370 0 5 10 15 20 Figure 7. Switching frquency vs. R1 and C2 fsw (KHz) D97IN784 500 2nF 1.2 15 20 25 VCC(V) Figure 8. Switching Frequency vs. input voltage. fsw (KHz) D98IN947 102.5 nF Tj=25°C 2.2 100.0 nF 50 10 105.0 0.8 100 5 107.5 Tamb=25°C 200 0 25 VCC(V) 3.3n F 97.5 4.7n F 20 95.0 5.6n F 10 5 6/11 92.5 90.0 0 20 40 60 80 R1(KΩ) 0 5 10 15 20 25 VCC(V) L5971 Figure 9. Switching frequency vs. junction temperature. fsw (KHz) D97IN785 Figure 10. Dropout voltage between pin 5 and 4. ∆V (V) D97IN736 Tj=125°C 0.5 105 0.4 C 5° =2 Tj 0.3 100 Tj=-25°C 0.2 95 0.1 0.0 90 -50 0 50 100 Figure 11. Efficiency vs output voltage. η (%) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Tj(°C) D98IN948 Figure 12. Efficiency vs. output current. D98IN949 η (%) 100KHz 96 V CC=8V 94 90 200KHz VCC=12V 92 VCC=18V 90 85 VCC=20V IO=1.5A 88 86 80 fsw=200KHz VO=5.1V 84 82 0 5 10 15 20 25 VO(V) Figure 13. Efficiency vs output current. η (%) D98IN950 75 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 14. Efficiency vs. output current. η (%) D98IN941 90 90 Vcc=8V 85 VCC=8V Vcc=12V 80 85 VCC=12V 75 VCC =18V 80 Vcc=18V 70 fsw=200KHz VO=3.36V 75 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Fsw=200KHz Vo=2.5V 65 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Io(A) 7/11 L5971 Figure 15. Load transient. Figure 16. Soft start capacitor selection vs. Inductor and Vccmax D98IN952 L (µH) fsw=100KHz 160 120 680nF 80 470nF nF 330 40 220nF 100nF 0 Figure 17. Soft start capacitor selection vs. Inductor and Vccmax L (µH) D98IN953 fsw=200KHz 20 22 24 26 28 V CCmax(V) Figure 18. Open loop frequency and phase of error amplifier. GAIN (dB) D97IN787 Phase 50 150 GAIN 100 56nF -50 45 90 -100 Phase 22nF 0 20 8/11 0 F 47n 33nF 50 0 22 24 26 28 VCCmax(V) -150 -200 10 135 102 103 104 10 5 10 6 107 108 f(Hz) L5971 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 3.18 OUTLINE AND MECHANICAL DATA 3.81 1.52 0.125 0.150 Minidip 0.060 9/11 L5971 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 H D 16 9 E 1 10/11 8 C L5971 Information furnished is believed to be accurate and reliable. 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