L4976 1A step down switching regulator Features ■ Up to 1A step down converter ■ Operating input voltage from 8v to 55v ■ Precise 5.1V reference voltage ■ Output voltage adjustable from 0.5V to 50V ■ Switching frequency adjustable up to 300kHz ■ Voltage feedforward ■ Zero load current operation ■ Internal current limiting (pulse-bypulse ■ and hiccup mode) ■ Protection against feedback disconnection ■ Thermal shutdown Figure 1. DIP8 SO16W 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 DMOS transistor (with a typical Rds(ON) of 0.25Ω) to obtain very high efficency and high switching speed. A switching frequency up to 300KHz 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 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. Typical 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 April 2007 Rev 7 L1 260µH (77120) 6 C6 100nF D1 GI SB360 VO=3.3V/1A C8 330µF 1/17 www.st.com 17 Contents L4976 Contents 1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 2.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.3 Operating temperature rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Typical charcteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2/17 L4976 1 Block diagram Block diagram Figure 2. Block diagram VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V COMP FB INTERNAL REFERENCE 7 8 6 3.3V E/A PWM R Q S 3.3V CBOOT CHARGE AT LIGHT LOADS DRIVE OSCILLATOR 3 OSC 1 GND BOOT 4 OUT 3/17 Pin settings L4976 2 Pin settings 2.1 Pin connection Figure 3. Pin connection (top view) 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. SO16 DIP8 2.2 Pin description Table 1. Pin description N° Pin Name Description DIP8 SO16W (1) 1 2 GND Ground 2 3 VREF 5.1V Reference voltage with 20mA current capability. 3 4 OSC 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) 4 5, 6 OUT Stepdown regulator output. 5 11 VCC Unregulated DC input voltage. 6 12 BOOT A capacitor connected between this pin and OUT allows to drive the internal VDMOS. 7 13 COMP E/A output to be used for frequency compensation. 8 14 FB 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. 1. Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 4/17 L4976 Electrical data 3 Electrical data 3.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Parameter DIP8 S016W V5 V11 V4 V5, V6 I4 I5, I6 V6-V5 V12-V11 V6 V12 V7 V8 Unit Input voltage 58 V Output DC voltage -1 V Output peak voltage at t = 0.1µs, f = 200kHz -5 V Maximum output current internal limit 14 V Bootstrap voltage 70 V V13 Analogs input voltage (VCC = 24V) 12 V (VCC = 20V) 6 V V14 -0.3 V DIP8 1 W SO16 0.8 W -40 to 150 °C PTOT TJ,TSTG 3.2 Value Power dissipation a TA ≤ 60°C Junction and storage temperature Thermal data Table 3. Thermal data Symbol Parameter DIP8 S016W Unit RthJA Maximum thermal resistance junction-ambient 90 (1) 110 (1) °C/W 1. Package mounted on board 3.3 Operating temperature rating Table 4. Operating temperature rating Symbol TJ Parameter Junction temperature range Value Unit -40 to 150 °C 5/17 Electrical characteristics 4 L4976 Electrical characteristics Table 5. Electrical characteristics (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol Parameter Test condition Min Typ Max Unit 55 V Dynamic characteristic VI VO Vd Operating input voltage range Output voltage Dropout voltage VO = 3.3 to 50V; IO = 1A (1) 8 IO = 0.5A 3.33 3.36 3.39 V IO = 0.2 to 1A 3.292 3.36 3.427 V VCC = 8 to 55V (1) 3.22 3.36 3.5 V 0.29 0.367 V 0.587 V 2.5 A VCC = 10V; IO = 1A (1) Il fs SVRR Maximum limiting current VCC = 8 to 55V (1) Efficiency VO = 3.3V; IO = 1A Switching frequency (1) 1.5 2 85 90 100 Supply voltage ripple rejection VI = VCC + 2VRMS; VO = Vref; IO = 1.A; fripple = 100Hz Voltage stability of switching frequency VCC = 8 to 55V 3 Temp. stability of switching frequency TJ = 0 to 125°C 4 % 110 60 KHz dB 6 % % Reference section Reference voltage Iref = 0 to 10mA; (1) 5.0 5.1 5.2 V 4.950 5.1 5.250 V 5 10 VCC = 8 to 55V Line regulation Iref = 0mA; mV VCC = 8 to 55V Load regulation Short circuit current 6/17 Vref = 0 to 5mA; 2 10 mV VCC = 0 to 20mA 6 25 mV 65 100 mA 30 L4976 Electrical characteristics Table 5. Electrical characteristics (continued) (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol Parameter Test condition Min Typ Max Unit 4 6 mA 2.5 3.5 mA 3.36 3.39 V 5 10 mV DC Characteristics Iqop Iq Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 3.8V Error Amplifier VFB Voltage feedback input RL Line regulation Ref. voltage stability vs temperature 3.33 VCC = 8 to 55V (1) mV/° C 0.4 VoH High level output voltage VFB = 2.5V VoL Low level output voltage VFB = 3.8V Source output current Vcomp = 6V; VFB = 2.5V 180 220 µA IO sink Sink output current Vcomp = 6V; VFB = 3.8V 200 300 µA Ib Source bias current IO source SVRR E/A gm 10.3 V 0.65 2 3 V µA Supply voltage ripple rejection Vcomp = Vfb; VCC = 8 to 55V 60 80 dB DC open loop gain RL = ∞ 50 57 dB Transconductance Icomp = -0.1 to 0.1mA Vcomp = 6V 2.5 ms Oscillator section Ramp valley Ramp peak 0.78 0.85 0.92 V VCC = 8V 2 2.15 2.3 V VCC = 55V 9 9.6 10.2 V 95 97 Maximum duty cycle Maximum frequency Duty cycle = 0% Rosc = 13kW, Cosc = 820pF % 300 kHz 1. Specification refered to Tj from 0 to 125°C 7/17 Typical charcteristics 5 L4976 Typical charcteristics Figure 4. Quiescent drain current vs. input voltage Iq (mA) D97IN724 200KHz R1=22K C2=1.2nF 5 Line regulation VO (V) 3.378 D97IN734 VCC=35V 3.376 3.374 100KHz R1=20K C2=2.7nF 4 Figure 5. Tj=25˚C 3.372 3.370 3 Tj=125˚C 3.368 0Hz 3.366 3.364 2 Tamb=25˚C 0% DC 3.362 3.360 1 0 Figure 6. 0 Vcc(V) 5 10 15 20 25 30 35 40 45 50 Quiescent current vs. junction Figure 7. temperature D97IN731 Iq (mA) 4 Switching frquency vs. R1 and C2 fsw (KHz) D97IN784 500 200KHz R1=22K C2=1.2nF 5 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Tamb=25˚C 0.8 2nF 200 1.2 100KHz R1=20K C2=2.7nF nF 100 2.2 nF 50 3 3.3n F 0Hz 2 4.7n F 20 VCC=35V 0% DC 5.6n F 10 5 1 -50 -30 -10 10 30 50 70 90 110 8/17 Tj(˚C) 0 20 40 60 80 R1(KΩ) L4976 Typical charcteristics Figure 8. Load regulation Figure 9. VO (V) D97IN733 3.377 Switching frequency vs. input voltage fsw (KHz) D97IN735 107.5 Tj=125˚C 105.0 3.376 102.5 3.375 Tj=25˚C Tj=25˚C 3.374 100.0 3.373 97.5 3.372 95.0 3.371 92.5 90.0 3.370 0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 10. Switching frequency vs. junction temperature fsw (KHz) 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 11. Efficiency vs. output current D97IN785 ∆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 Tj(˚C) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 12. Dropout voltage between pin 5 Figure 13. Efficiency vs. output current and 4 ∆V (V) 0.5 D97IN736 Tj=125˚C η (%) D97IN739 VCC=8V 90 85 0.4 =2 Tj VCC=12V C 5˚ VCC=24V 80 0.3 VCC=48V 75 0.2 Tj=-25˚C 70 0.1 fsw=100KHz VO=3.36V 65 60 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 9/17 Typical charcteristics L4976 Figure 14. Efficiency vs output voltage η (%) D97IN737 100KHz 96 94 Figure 15. Efficiency vs. output current D97IN740 η (%) VCC=8V 90 200KHz VCC=12V VCC=24V 85 92 80 VCC=48V 90 75 VCC=35V IO=1.5A 88 86 70 84 65 82 0 5 10 15 20 25 VO(V) Figure 16. Efficiency vs. output current η (%) D97IN741 fsw=200KHz VO=5.1V 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 17. Efficiency vs. Vo Pdiss (mW) D97IN744 VCC=35V fsw=100KHz VCC=8V 90 800 85 VCC=12V 80 IO=1.5A 600 VCC=24V 75 IO=1A 400 70 VCC=48V IO=0.5A 65 fsw=200KHz VO=3.36V 200 60 55 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 18. Efficiency vs. VCC 0 0 5 10 D97IN742 Ilim (A) V0 85 25 30 V0(V) D97IN747 V0 =5 SW =1 20 Figure 19. Pulse by pulse limiting current vs. junction temperature. η (%) .1V-f 15 fsw=100KHz VCC=35V 2.9 00KH z =5 .1V 2.8 -fS W= 20 V0 = 0K Hz 2.7 3.36 80 V-f SW = V 0 =3 .36 100 V- fS KHz W= 20 2.5 0K 75 2.6 Hz IO=1.5A 2.4 70 10/17 2.3 0 10 20 30 40 50 VCC(V) -50 -25 0 25 50 75 100 125 Tj(˚C) L4976 Typical charcteristics Figure 20. Power dissipation vs. VCC Pdiss (mW) Figure 21. Load transient D97IN743 VO=5.1V fsw=100KHz 800 IO=1.5A 600 IO=1A 400 IO=0.5A 200 0 0 10 20 30 40 50 VCC(V) Figure 22. Line transient VCC (V) Figure 23. Open loop frequency and phase of error amplifier GAIN (dB) D97IN786 D97IN787 Phase 30 50 GAIN 20 0 0 VO (mV) -50 45 100 -100 10 1 IO = 1A fsw = 100KHz 2 90 Phase 0 135 -150 -100 1ms/DIV -200 10 102 103 104 105 106 107 108 f(Hz) 11/17 Package mechanical data 6 L4976 Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com 12/17 L4976 Package mechanical data Figure 24. DIP8 mechanical data & package dimensions mm inch DIM. MIN. A TYP. 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 DIP-8 0.060 13/17 Package mechanical data L4976 Figure 25. SO16Wide mechanical data & package dimensions mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.10 0.30 0.004 0.012 B 0.33 0.51 0.013 0.200 C 0.23 0.32 0.009 0.013 D (1) 10.10 10.50 0.398 0.413 E 7.40 7.60 0.291 0.299 e 1.27 0.050 H 10.0 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 L 0.40 1.27 0.016 0.050 k ddd OUTLINE AND MECHANICAL DATA 0˚ (min.), 8˚ (max.) 0.10 0.004 (1) “D” dimension does not include mold flash, protusions or gate burrs. Mold flash, protusions or gate burrs shall not exceed 0.15mm per side. SO16 (Wide) 0016021 C 14/17 L4976 7 Order code Order code Table 6. Order code Part number Package Packaging L4976 DIP8 Tube L4976D SO16W Tube L4976D013TR SO16W Tape and reel 15/17 Revision history 8 L4976 Revision history Table 7. Revision history 16/17 Date Revision Changes 5-Aug-2001 6 First Issue 3-Apr-2007 7 Document reformatted, updated dropout voltage values in Table 5 on page 6 L4976 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. 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