L4976

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 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. Figure 1. Typical application circuit 5 R1 20K 3 C1 220µF 63V C7 220nF C2 2.7nF 2 7 Vi=8V to 55V 8 L4976 4 1 6 L1 260µH (77120) D1 GI SB360 C8 330µF VO=3.3V/1A R2 9.1K C4 22nF C6 100nF April 2007 Rev 7 1/17 www.st.com 17 Contents L4976 Contents 1 2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 2.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 3.2 3.3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Operating temperature rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 5 6 7 8 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Typical charcteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2/17 L4976 Block diagram 1 Block diagram Figure 2. 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 1 GND CBOOT CHARGE AT LIGHT LOADS INTERNAL REFERENCE 6 BOOT 3.3V 3 OSC 4 OUT 3/17 Pin settings L4976 2 2.1 Pin settings Pin connection Figure 3. Pin connection (top view) N.C. 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 GND VREF OSC OUT OUT N.C. N.C. DIP8 SO16 2.2 Pin description Table 1. Pin description N° Pin DIP8 1 2 SO16W (1) 2 3 Name GND VREF 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. Description 3 4 OSC 4 5 6 7 8 5, 6 11 12 13 14 OUT VCC BOOT COMP FB 1. Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. 4/17 L4976 Electrical data 3 3.1 Electrical data Maximum ratings Table 2. Absolute maximum ratings Symbol Parameter DIP8 V5 V4 I4 V6-V5 V6 V7 V8 S016W V11 V5, V6 I5, I6 V12-V11 V12 V13 V14 Bootstrap voltage Analogs input voltage (VCC = 24V) (VCC = 20V) Power dissipation a TA ≤ 60°C Junction and storage temperature DIP8 SO16 Input voltage Output DC voltage Output peak voltage at t = 0.1µs, f = 200kHz Maximum output current 58 -1 -5 internal limit 14 70 12 6 -0.3 1 0.8 -40 to 150 V V V V V W W °C V V V Value Unit PTOT TJ,TSTG 3.2 Thermal data Table 3. Thermal data Symbol RthJA Parameter Maximum thermal resistance junction-ambient DIP8 90 (1) S016W 110 (1) Unit °C/W 1. Package mounted on board 3.3 Operating temperature rating Table 4. Operating temperature rating Symbol TJ Parameter Junction temperature range Value -40 to 150 Unit °C 5/17 Electrical characteristics L4976 4 Electrical characteristics Table 5. Electrical characteristics (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol Dynamic characteristic VI Operating input voltage range VO = 3.3 to 50V; IO = 1A (1) IO = 0.5A VO Output voltage IO = 0.2 to 1A VCC = 8 to 55V (1) Vd Il Parameter Test condition Min Typ Max Unit 8 3.33 3.292 3.22 3.36 3.36 3.36 0.29 55 3.39 3.427 3.5 0.367 0.587 V V V V V V A % Dropout voltage Maximum limiting current Efficiency VCC = 10V; IO = 1A (1) VCC = 8 to 55V (1) VO = 3.3V; IO = 1A (1) 1.5 2 85 2.5 fs Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency 90 60 100 110 KHz dB SVRR VI = VCC + 2VRMS; VO = Vref; IO = 1.A; fripple = 100Hz VCC = 8 to 55V TJ = 0 to 125°C 3 4 6 % % Reference section Reference voltage Iref = 0 to 10mA; (1) VCC = 8 to 55V Line regulation Iref = 0mA; VCC = 8 to 55V Load regulation Short circuit current Vref = 0 to 5mA; VCC = 0 to 20mA 30 2 6 65 10 25 100 mV mV mA 5 10 mV 5.0 4.950 5.1 5.1 5.2 5.250 V V 6/17 L4976 Electrical characteristics Table 5. Electrical characteristics (continued) (TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.) Symbol DC Characteristics Iqop Iq Parameter Test condition Min Typ Max Unit Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 3.8V 4 2.5 6 3.5 mA mA Error Amplifier VFB RL Voltage feedback input Line regulation Ref. voltage stability vs temperature VoH VoL IO source IO sink Ib 3.33 VCC = 8 to 55V (1) 3.36 5 0.4 3.39 10 V mV mV/° C V 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 VFB = 2.5V VFB = 3.8V Vcomp = 6V; VFB = 2.5V Vcomp = 6V; VFB = 3.8V 10.3 0.65 180 200 220 300 2 3 V µA µA µA dB dB ms SVRR E/A Vcomp = Vfb; VCC = 8 to 55V RL = ∞ Icomp = -0.1 to 0.1mA Vcomp = 6V 60 50 80 57 2.5 gm Transconductance Oscillator section Ramp valley Ramp peak Maximum duty cycle Maximum frequency 1. Specification refered to Tj from 0 to 125°C 0.78 VCC = 8V VCC = 55V 2 9 95 Duty cycle = 0% Rosc = 13kW, Cosc = 820pF 0.85 2.15 9.6 97 0.92 2.3 10.2 V V V % 300 kHz 7/17 Typical charcteristics L4976 5 Typical charcteristics Figure 4. Iq (mA) 200KHz R1=22K C2=1.2nF 100KHz R1=20K C2=2.7nF Quiescent drain current vs. input voltage D97IN724 Figure 5. VO (V) 3.378 3.376 3.374 Line regulation D97IN734 VCC=35V 5 Tj=25˚C 4 3.372 3.370 Tj=125˚C 3 0Hz 3.368 3.366 2 Tamb=25˚C 0% DC 3.364 3.362 3.360 0 5 10 15 20 25 30 35 40 45 50 Vcc(V) 1 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 6. Quiescent current vs. junction Figure 7. temperature D97IN731 Switching frquency vs. R1 and C2 D97IN784 Iq (mA) 5 fsw (KHz) 500 0.8 200KHz R1=22K C2=1.2nF 100KHz R1=20K C2=2.7nF 0Hz Tamb=25˚C 200 100 50 20 2nF 1.2 nF 2.2 nF 4 3 VCC=35V 0% DC 3.3n F 4.7n F 2 5.6n F 10 1 -50 -30 -10 10 30 50 70 90 110 Tj(˚C) 5 0 20 40 60 80 R1(KΩ) 8/17 L4976 Figure 8. VO (V) 3.377 Tj=125˚C Typical charcteristics Load regulation D97IN733 Figure 9. fsw (KHz) 107.5 105.0 102.5 Tj=25˚C Switching frequency vs. input voltage D97IN735 3.376 3.375 3.374 3.373 3.372 3.371 3.370 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Tj=25˚C 100.0 97.5 95.0 92.5 90.0 0 5 10 15 20 25 30 35 40 45 50 VCC(V) Figure 10. Switching frequency vs. junction temperature fsw (KHz) D97IN785 Figure 11. Efficiency vs. output current ∆V (V) 0.5 Tj=125˚C D97IN736 105 0.4 Tj =2 5˚ C 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 12. Dropout voltage between pin 5 Figure 13. Efficiency vs. output current and 4 ∆V (V) 0.5 0.4 Tj =2 Tj=125˚C D97IN736 η (%) 90 85 VCC=12V VCC=24V VCC=8V D97IN739 C 5˚ 80 75 VCC=48V 0.3 0.2 0.1 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Tj=-25˚C 70 65 60 fsw=100KHz VO=3.36V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 9/17 Typical charcteristics Figure 14. Efficiency vs output voltage η (%) 96 94 92 100KHz 200KHz D97IN737 L4976 Figure 15. Efficiency vs. output current η (%) 90 85 80 VCC=12V VCC=24V D97IN740 VCC=8V 90 88 86 84 82 0 5 10 15 20 25 VO(V) VCC=35V IO=1.5A VCC=48V 75 70 65 60 fsw=200KHz VO=5.1V 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) Figure 16. Efficiency vs. 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) VCC=8V D97IN741 Figure 17. Efficiency vs. Vo Pdiss (mW) VCC=35V fsw=100KHz D97IN744 800 VCC=12V VCC=24V IO=1.5A 600 IO=1A 400 VCC=48V fsw=200KHz VO=3.36V IO=0.5A 200 0 0 5 10 15 20 25 30 V0(V) Figure 18. Efficiency vs. VCC Figure 19. Pulse by pulse limiting current vs. junction temperature. D97IN742 η (%) V0 =5 .1V-f SW =1 Ilim (A) 2.9 2.8 fsw=100KHz VCC=35V D97IN747 00KH z 85 V0 =5 .1V -fS W= 20 0K V0 = Hz 100 2.7 KHz 80 3.36 V V-f 0 =3 SW = .36 2.6 2.5 V- fS W= 75 20 0K IO=1.5A Hz 2.4 70 2.3 0 10 20 30 40 50 VCC(V) -50 -25 0 25 50 75 100 125 Tj(˚C) 10/17 L4976 Figure 20. Power dissipation vs. VCC Pdiss (mW) VO=5.1V fsw=100KHz D97IN743 Typical charcteristics Figure 21. Load transient 800 600 IO=1.5A IO=1A 400 IO=0.5A 200 0 0 10 20 30 40 50 VCC(V) Figure 22. Line transient VCC (V) 30 D97IN786 Figure 23. Open loop frequency and phase of error amplifier GAIN (dB) 50 D97IN787 Phase 20 0 GAIN 0 45 90 Phase 10 1 IO = 1A fsw = 100KHz VO (mV) 100 0 -50 -100 -150 2 135 -100 1ms/DIV -200 10 102 103 104 105 106 107 108 f(Hz) 11/17 Package mechanical data L4976 6 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 Figure 24. DIP8 mechanical data & package dimensions mm DIM. MIN. A a1 B b b1 D E e e3 e4 F I L Z 3.18 7.95 2.54 7.62 7.62 6.6 5.08 3.81 1.52 0.125 0.51 1.15 0.356 0.204 1.65 0.55 0.304 10.92 9.75 0.313 0.100 0.300 0.300 0.260 0.200 0.150 0.060 TYP. 3.32 0.020 0.045 0.014 0.008 0.065 0.022 0.012 0.430 0.384 MAX. MIN. TYP. 0.131 MAX. inch Package mechanical data OUTLINE AND MECHANICAL DATA DIP-8 13/17 Package mechanical data Figure 25. SO16Wide mechanical data & package dimensions mm DIM. MIN. A A1 B C D (1) E e H h L k ddd 10.0 0.25 0.40 2.35 0.10 0.33 0.23 10.10 7.40 1.27 10.65 0.75 1.27 0.394 0.010 0.016 TYP. MAX. 2.65 0.30 0.51 0.32 10.50 7.60 MIN. 0.093 0.004 0.013 0.009 0.398 0.291 0.050 0.419 0.030 0.050 TYP. MAX. 0.104 0.012 0.200 0.013 0.413 0.299 inch L4976 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 Order code 7 Order code Table 6. Order code Part number L4976 L4976D L4976D013TR Package DIP8 SO16W SO16W Packaging Tube Tube Tape and reel 15/17 Revision history L4976 8 Revision history Table 7. Revision history Date 5-Aug-2001 3-Apr-2007 Revision 6 7 First Issue Document reformatted, updated dropout voltage values in Table 5 on page 6 Changes 16/17 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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