L4976D

® 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 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 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. Vi=8V to 55V 5 R1 20K 3 C1 220µF 63V C7 220nF C2 2.7nF 2 7 8 L4976 4 1 6 L1 260µH (77120) D1 GI SB360 C8 330µF VO=3.3V/1A R2 9.1K C4 22nF C6 100nF May 2000 1/11 L4976 BLOCK DIAGRAM VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V COMP FB 7 8 E/A 3.3V PWM R S Q DRIVE OSCILLATOR CBOOT CHARGE AT LIGHT LOADS INTERNAL REFERENCE 6 BOOT 3.3V 3 OSC 1 GND 4 OUT PIN CONNECTIONS N.C. GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 N.C. N.C. FB COMP BOOT VCC N.C. N.C. GND VREF OSC OUT 1 2 3 4 8 7 6 5 FB COMP BOOT VCC VREF OSC OUT OUT N.C. N.C. Minidip SO16W PIN FUNCTIONS DIP 1 2 3 SO (*) 2 3 4 Name GND VREF OSC 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. 4 5 6 7 8 5, 6 11 12 13 14 OUT VCC BOOT COMP FB (*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 2/11 L4976 THERMAL DATA Symbol R th(j-amb) Parameter Thermal Resistance Junction to ambient Max. Minidip 90 (*) SO16 110 (*) Unit °C/W (*) Package mounted on board. OPERATING TEMPERATURE RATING Symbol TJ Parameter Junction Temperature Range Value -40 to 150 Unit °C ABSOLUTE MAXIMUM RATINGS Symbol Minidip V5 V4 I4 V6-V5 V6 V7 V8 Ptot Tj,Tstg S016 V11 V5,V6 I5,I6 V12-V11 V12 V13 V14 Bootstrap voltage Analogs input voltage (VCC = 24V) (VCC = 20V) Power dissipation a Tamb ≤ 60°C Junction and storage temperature Minidip SO16 Input voltage Output DC voltage Output peak voltage at t = 0.1µs f=200KHz Maximum output current Parameter Value 58 -1 -5 int. limit. 14 70 12 6 -0.3 1 0.8 -40 to 150 V V V V V W W °C Unit V V 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 VI Vo Parameter Operating input voltage range Output voltage Test Condition 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 Vi = Vcc+2VRMS; Vo = Vref; Io = 1.A; f ripple = 100Hz Vcc = 8 to 55V Tj = 0 to 125°C * Min. 8 3.33 3.292 3.22 Typ. Max. 55 3.39 3.427 3.5 0.55 0.88 2.5 110 Unit V V V V V V A % KHz dB % % DYNAMIC CHARACTERISTIC 3.36 3.36 3.36 0.44 2 85 100 * * * * Vd Il fs SVRR Dropout voltage Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency 1.5 90 60 3 4 6 3/11 L4976 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Reference Section Reference Voltage Test Condition Min. 5.0 4.950 Typ. 5.1 5.1 5 2 6 65 Max. 5.2 5.250 10 10 25 100 Unit V V mV mV mV mA Line Regulation Load Regulation Short Circuit Current Iref = 0 to 10mA; VCC = 8 to 55V Iref = 0mA; VCC = 8 to 55V Vref = 0 to 5mA; VCC = 0 to 20mA * 30 DC Characteristics Iqop Iq VFB RL Total operating quiescent current Quiescent current 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 4 Duty Cycle = 0; VFB = 3.8V 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 2.5 3.36 5 0.4 6 3.5 3.39 10 mA mA V mV mV/°C V V µA µA µA dB dB ms Error Amplifier VoH VoL Io source Io sink Ib SVRR E/A gm 3 Oscillator Section Ramp Valley Ramp peak Maximum duty cycle Maximum Frequency 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 4/11 L4976 Figure 1. Quiescent drain current vs. input voltage. Iq (mA) 200KHz R 1=22K C 2=1.2nF 100KHz R 1=20K C 2=2.7nF D97IN724 Figure 2. Quiescent current vs. junction temperature Iq (mA) 5 D97IN731 5 200KHz R1=22K C2=1.2nF 100KHz R1 =20K C2 =2.7nF 0Hz 4 4 3 0Hz 3 VCC=35V 0% DC 2 Tamb=25°C 0% DC 2 1 0 5 10 15 20 25 30 35 40 45 50 Vcc(V) 1 -50 -30 -10 10 30 50 70 90 110 Tj( °C) Figure 3. Line Regulation VO (V) 3.377 3.376 3.375 Tj=25°C Tj=125°C D97IN733 Figure 4. Load regulation VO (V) 3.378 3.376 3.374 3.372 3.370 3.368 3.366 3.364 Tj=125°C Tj=25°C D97IN734 VCC=35V 3.374 3.373 3.372 3.371 3.370 0 5 10 15 20 25 30 35 40 45 50 VCC(V) 3.362 3.360 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 I O(A) Figure 5. Switching frquency vs. R1 and C2 fsw (KHz) 500 0.8 Figure 6. Switching Frequency vs. input voltage. fsw (KHz) 107.5 105.0 D97IN735 D97IN784 Tamb=25°C 200 100 50 20 2nF 1.2 nF 102.5 nF F Tj=25°C 2.2 100.0 97.5 4.7n F 3.3n 5.6n F 95.0 92.5 10 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) 0.5 Tj=125°C D97IN736 105 0.4 Tj =2 C 5° 100 0.3 0.2 Tj=-25°C 95 0.1 0.0 90 -50 0 50 100 Tj( °C) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 9. Efficiency vs output voltage. η (%) 96 94 92 100KHz D97IN737 Figure 10. Efficiencyvs. output current. η (%) 90 85 VCC=24V VCC=12V D97IN738 VCC=8V 200KHz 80 90 88 86 84 82 0 5 10 15 20 25 VO(V) VCC=35V IO=1.5A 75 70 65 VCC =48V 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 11. Efficiencyvs. output current. η (%) 90 85 80 75 70 65 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) VCC=48V VCC =12V VCC=24V VCC=8V D97IN739 Figure 12. Efficiencyvs. output current. η (%) 90 85 80 V CC=48V V CC=12V VCC=24V D97IN740 VCC=8V 75 fsw=100KHz VO=3.36V 70 65 60 fsw=200KHz V O=5.1V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 6/11 L4976 Figure 13. Efficiencyvs. output current. η (%) 90 85 80 75 70 65 60 55 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 70 0 10 20 30 40 50 VCC(V) VCC=48V fsw=200KHz VO=3.36V VCC=8V VCC=12V VCC=24V V0 = D97IN741 Figure 14. Efficiencyvs. Vcc. η (%) V0 =5 .1V-f SW =10 D97IN742 0KHz 85 V0 = 5.1 V-f SW =2 00 KH z 100 80 3.36 -fS V V-f 0= 3.3 SW = 6V KHz W= 75 12 0 0K IO=1.5A Hz Figure 15. Power dissipation vs. Vcc. Pdiss (mW) V O=5.1V fsw=100KHz D97IN743 Figure 16. Efficiencyvs. Vo. Pdiss (mW) VCC=35V fsw=100KHz D97IN744 800 800 IO=1.5A IO=1.5A IO=1A 600 600 IO=1A 400 IO=0.5A 400 IO=0.5A 200 200 0 0 10 20 30 40 50 VCC(V) 0 0 5 10 15 20 25 30 V0(V) Figure 17. Pulse by pulse limiting current vs. junction temperature. Ilim (A) 2.9 2.8 2.7 2.6 2.5 2.4 2.3 -50 -25 0 25 50 fsw=100KHz VCC=35V D97IN747 Figure 18. Load transient. 75 100 125 Tj(°C) 7/11 L4976 Figure 19. Line transient. VCC (V) 30 D97IN786 Figure 20. Open loop frequency and phase of error amplifier GAIN (dB) 50 D97IN787 Phase 20 10 1 I O = 1A f sw = 100KHz GAIN 0 0 45 90 Phase VO (mV) 100 -50 -100 2 0 -100 1ms/DIV -150 -200 10 135 102 103 104 10 5 10 6 10 7 108 f(Hz) 8/11 L4976 DIM. MIN. A a1 B b b1 D E e e3 e4 F I L Z 3.18 7.95 0.51 1.15 0.356 0.204 mm TYP. 3.32 0.020 1.65 0.55 0.304 10.92 9.75 2.54 7.62 7.62 6.6 5.08 3.81 1.52 0.125 0.313 0.045 0.014 0.008 MAX. MIN. inch TYP. 0.131 MAX. OUTLINE AND MECHANICAL DATA 0.065 0.022 0.012 0.430 0.384 0.100 0.300 0.300 0.260 0.200 0.150 0.060 Minidip 9/11 L4976 DIM. MIN. A A1 B C D E e H h L K 10 0.25 0.4 2.35 0.1 0.33 0.23 10.1 7.4 mm TYP. MAX. 2.65 0.3 0.51 0.32 10.5 7.6 1.27 10.65 0.75 1.27 0.394 0.010 0.016 MIN. 0.093 0.004 0.013 0.009 0.398 0.291 inch TYP. MAX. 0.104 0.012 0.020 0.013 0.413 0.299 0.050 0.419 0.030 0.050 OUTLINE AND MECHANICAL DATA 0° (min.)8° (max.) SO16 Wide L h x 45 A B e K H D A1 C 16 9 E 1 8 10/11 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. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. 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