L4976 1A STEP DOWN SWITCHING REGULATOR UP TO 1A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 5.1V 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) PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN Minidip SO16W ORDERING NUMBERS: L4976 (Minidip) L4976D (SO16) ages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 40V 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, protection against feedback loop disconnection and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16W for SMD assembly. DESCRIPTION The L4976 is a step down monolithic power switching regulator delivering 1A 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. A switching frequency up to 250KHz is achievable (the maximum power dissipation of the packTYPICAL APPLICATION CIRCUIT Vi=8V to 55V 5 8 R1 20K L4976 3 C1 220µF 63V C7 220nF C2 2.7nF 2 4 1 7 R2 9.1K C4 22nF May 2000 L1 260µH (77120) 6 C6 100nF D1 GI SB360 VO=3.3V/1A C8 330µF 1/11 L4976 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V COMP FB INTERNAL REFERENCE 7 6 3.3V E/A 8 PWM 3.3V R Q S CBOOT CHARGE AT LIGHT LOADS DRIVE OSCILLATOR 1 3 OSC BOOT 4 GND OUT PIN CONNECTIONS GND 1 8 FB VREF 2 7 COMP OSC 3 6 BOOT OUT 4 5 VCC N.C. 1 16 N.C. GND 2 15 N.C. VREF 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. Minidip SO16W PIN FUNCTIONS DIP 1 2 3 SO (*) 2 3 4 Name GND VREF OSC 4 5 6 7 8 5, 6 11 12 13 14 OUT VCC BOOT COMP FB Function Ground 5.1V Reference voltage with 20mA current capability. 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 VDMOS 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. 2/11 L4976 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. OPERATING TEMPERATURE RATING Symbol Parameter Junction Temperature Range TJ Value Unit -40 to 150 °C ABSOLUTE MAXIMUM RATINGS Symbol Minidip Parameter S016 Value Unit V5 V11 V4 V5,V6 I4 I5,I6 V6-V5 V12-V11 V6 V12 Bootstrap voltage 70 V V7 V13 Analogs input voltage (VCC = 24V) 12 V V8 V14 (VCC = 20V) 6 -0.3 V V Minidip 1 W SO16 0.8 W -40 to 150 °C Ptot Tj,Tstg Input voltage 58 V Output DC voltage Output peak voltage at t = 0.1µs f=200KHz -1 -5 V V 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 2.5 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 = 1A Io = 0.5A Io = 0.2 to 1A Vcc = 8 to 55V Vcc = 10V; Io = 1A Vcc = 8 to 55V Vo = 3.3V; Io = 1A * * 8 3.33 3.292 3.22 * * 1.5 * Vi = Vcc+2VRMS; Vo = Vref; Io = 1.A; f ripple = 100Hz Vcc = 8 to 55V Tj = 0 to 125°C 90 60 3.36 3.36 3.36 0.44 2 85 100 3 4 110 6 % % 3/11 L4976 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Reference Section Reference Voltage Line Regulation Load Regulation Test Condition Iref = 0 to 10mA; VCC = 8 to 55V Iref = 0mA; VCC = 8 to 55V Vref = 0 to 5mA; VCC = 0 to 20mA * Short Circuit Current Min. Typ. Max. Unit 5.0 4.950 5.1 5.1 5.2 5.250 V V 5 10 mV 2 6 65 10 25 100 mV mV mA 4 6 mA 2.5 3.5 mA 3.36 5 0.4 3.39 10 V mV mV/°C 30 DC Characteristics Iqop Iq Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 3.8V 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 0.65 180 200 60 50 220 300 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 4/11 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 L4976 Figure 1. Quiescent drain current vs. input voltage. Iq (mA) D97IN724 200KHz R 1=22K C 2=1.2nF 5 Figure 2. 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 Vcc(V) Figure 3. Line Regulation -50 -30 -10 10 30 50 70 90 110 Tj(°C) Figure 4. Load regulation VO (V) D97IN733 3.377 Tj=125°C VO (V) 3.378 D97IN734 VCC=35V 3.376 3.376 3.374 Tj=25°C 3.375 3.372 Tj=25°C 3.374 3.370 3.373 3.368 Tj=125°C 3.366 3.372 3.364 3.371 3.362 3.370 3.360 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 5. Switching frquency vs. R1 and C2 fsw (KHz) D97IN784 500 Tamb=25°C 2nF Figure 6. Switching Frequency vs. input voltage. fsw (KHz) D97IN735 105.0 1.2 nF 100 0.2 0.4 0.6 0.8 1.0 1.2 1.4 I O(A) 107.5 0.8 200 0 102.5 Tj=25°C 2.2 nF 50 100.0 3.3n F 97.5 4.7n F 20 95.0 5.6n F 10 5 92.5 0 20 40 60 80 R1(KΩ) 90.0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) 5/11 L4976 Figure 7. Switching frequency vs. junction temperature. fsw (KHz) D97IN785 Figure 8. 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 9. Efficiency vs output voltage. η (%) D97IN737 100KHz 96 94 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Tj(°C) Figure 10. Efficiencyvs. output current. η (%) D97IN738 VCC=8V VCC=12V 90 200KHz 85 92 VCC=24V 80 90 86 70 84 65 82 0 5 10 15 20 25 VO(V) Figure 11. Efficiencyvs. output current. η (%) D97IN739 VCC=8V 90 85 VCC =48V 75 VCC=35V IO=1.5A 88 fsw=100KHz VO=5.1V 60 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 12. Efficiencyvs. output current. D97IN740 η (%) VCC=8V 90 VCC =12V V CC=12V VCC=24V 85 VCC=24V 80 80 V CC=48V VCC=48V 75 70 75 fsw=100KHz VO=3.36V 65 60 6/11 70 fsw=200KHz V O=5.1V 65 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) L4976 Figure 13. Efficiencyvs. output current. η (%) D97IN741 Figure 14. Efficiencyvs. Vcc. η (%) D97IN742 V0 =5 .1V-f VCC=8V 90 85 SW =10 V0 = 85 VCC=12V 0KHz 5.1 V-f SW 80 VCC=24V =2 00 V0 = 75 KH 3.36 80 z V-f V SW = 0= 3.3 100 KHz 6V 70 -fS VCC=48V W= 65 fsw=200KHz VO=3.36V 12 0 0K 75 Hz IO=1.5A 60 55 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 15. Power dissipation vs. Vcc. Pdiss (mW) D97IN743 70 0 10 20 30 40 50 VCC(V) Figure 16. Efficiencyvs. Vo. Pdiss (mW) D97IN744 V O=5.1V fsw=100KHz VCC=35V fsw=100KHz 800 800 IO=1.5A IO=1.5A 600 600 IO=1A 400 IO=1A 400 IO=0.5A 200 0 IO=0.5A 200 0 10 20 30 40 50 VCC(V) Figure 17. Pulse by pulse limiting current vs. junction temperature. Ilim (A) 0 0 5 10 15 20 25 30 V0(V) Figure 18. Load transient. D97IN747 fsw=100KHz VCC=35V 2.9 2.8 2.7 2.6 2.5 2.4 2.3 -50 -25 0 25 50 75 100 125 Tj(°C) 7/11 L4976 Figure 19. Line transient. VCC (V) Figure 20. Open loop frequency and phase of error amplifier D97IN786 GAIN (dB) D97IN787 Phase 30 50 20 GAIN 10 VO (mV) 1 I O = 1A f sw = 100KHz 2 0 0 -50 45 -100 90 100 0 -100 Phase -150 135 1ms/DIV -200 10 8/11 102 103 104 10 5 10 6 10 7 108 f(Hz) L4976 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 L4976 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 L4976 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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