L4960 ® 2.5A POWER SWITCHING REGULATOR 2.5A OUTPUT CURRENT 5.1V TO 40V OPUTPUT VOLTAGE RANGE PRECISE (± 2%) ON-CHIP REFERENCE HIGH SWITCHING FREQUENCY VERY HIGH EFFICIENCY (UP TO 90%) VERY FEW EXTERNAL COMPONENTS SOFT START INTERNAL LIMITING CURRENT THERMAL SHUTDOWN DESCRIPTION The L4960 is a monolithic power switching regulator delivering 2.5A at a voltage variable from 5V to 40V in step down configuration. Features of the device include current limiting, soft start, thermal protection and 0 to 100% duty cycle for continuous operation mode. HEPTAWATT ORDERING NUMBERS: L4960 (Vertical) L4960H (Horizontal) The L4960 is mounted in a Heptawatt plastic power package and requires very few external components. Efficient operation at switching frequencies up to 150KHz allows a reduction in the size and cost of external filter components. BLOCK DIAGRAM June 2000 1/16 L4960 PIN CONNECTION (Top view) ABSOLUTE MAXIMUM RATINGS Symbol V1 V1 - V7 V7 V3, V6 V2 I3 I5 Ptot Tj, Tstg Parameter Input voltage Input to output voltage difference Negative output DC voltage Negative output peak voltage at t = 0.1µs; f = 100KHz Voltage at pin 3 and 6 Voltage at pin 2 Pin 3 sink current Pin 5 source current Power dissipation at Tcase ≤ 90°C Junction and storage temperature Value 50 50 -1 -5 5.5 7 1 20 15 -40 to 150 Unit V V V V V V mA mA W °C PIN FUNCTIONS FUNCTION N° NAME 1 SUPPLY VOLTAGE Unregulated voltage input. An internal regulator powers the internal logic. 2 FEEDBACK INPUT The feedback terminal of the regulation loop. The output is connected directly to this terminal for 5.1V operation; it is connected via a divider for higher voltages. 3 FREQUENCY COMPENSATION A series RC network connected between this terminal and ground determines the regulation loop gain characteristics. 4 GROUND Common ground terminal. 5 OSCILLATOR A parallel RC network connected to this terminal determines the switching frequency. 6 SOFT START Soft start time constant. A capacitor is connected between this terminal and ground to define the soft start time constant. This capacitor also determines the average short circuit output current. 7 OUTPUT Regulator output. 2/16 L4960 THERMAL DATA Symbol Parameter Value Unit Rth j-case Thermal resistance junction-case max 4 °C/W Rth j-amb Thermal resistance junction-ambient max 50 °C/W ELECTRICAL CHARACTERISTICS (Refer to the test circuit, Tj = 25 °C, Vi = 35V, unless otherwise specified) Symbol Parameter Test Conditions Min. Typ. Max. Unit Vref 40 V 9 46 V DYNAMIC CHARACTERISTICS Vo Output voltage range Vi = 46V Io = 1A Vi Input voltage range Vo = Vref to 36V Io = 2.5A ∆ Vo Line regulation Vi = 10V to 40V ∆ Vo Load regulation Vref ∆ Vref ∆T Io = 1A 15 50 mV Vo = Vref Io = 0.5A to 2A 10 30 mV Internal reference voltage (pin 2) Vi = 9V to 46V Io = 1A 5.1 5.2 V Average temperature coefficient of refer voltage Tj = 0°C to 125°C Io = 1A 0.4 Vd Dropout voltage Io = 2A 1.4 Iom Maximum operating load current Vi = 9V to 46V Vo = Vref to 36V I7L Current limiting threshold (pin 7) Vi = 9V to 46V Vo = Vref to 36V ISH Input average current Vi = 46V; Efficiency η SVR Supply voltage ripple rejection Vo = Vref 5 mV/°C 3 2.5 V A 3 4.5 A 60 mA output short-circuit 30 f = 100KHz Vo = Vref 75 % Io = 2A Vo = 12V 85 % 50 56 dB 85 100 ∆ Vi = 2Vrms fripple = 100Hz Vo = Vref f Switching frequency ∆f ∆ Vi Voltage stability of switching frequency Vi = 9V to 46V ∆f ∆ Tj Temperature stability of switching frequency Tj = 0°C to 125°C fmax Maximum operating switching frequency Vo = Vref Tsd Thermal shutdown junction temperature Io = 1A Io = 2A 120 115 KHz 0.5 % 1 % 150 KHz 150 °C 3/16 L4960 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Test Conditions Min. Typ. Max. Unit 30 40 mA 15 20 mA 1 mA DC CHARACTERISTICS I1Q Quiescent drain current 100% duty cycle pins 5 and 7 open Vi = 46V 0% duty cycle -I7L Output leakage current 0% duty cycle SOFT START I6SO Source current 100 140 180 µA I6SI Sink current 50 70 120 µA ERROR AMPLIFIER V3H High level output voltage V2 = 4.7V I3 = 100µA V3L Low level output voltage V2 = 5.3V I3 = 100µA I3SI Sink output current V2 = 5.3V 100 150 µA Source output current V2 = 4.7V 100 150 µA I2 Input bias current V2 = 5.2V Gv DC open loop gain V3 = 1V to 3V -I3SO 3.5 V 0.5 2 46 55 10 V µA dB OSCILLATOR -I5 4/16 Oscillator source current 5 mA L4960 CIRCUIT OPERATION (refer to the block diagram) The L4960 is a monolithic stepdown switching regulator providing output voltages from 5.1V to 40V and delivering 2.5A. The regulation loop consists of a sawtooth oscillator, error amplifier, comparator and the output stage. An error signal is produced by comparing the output voltage with a precise 5.1V on-chip reference (zener zap trimmed to ± 2%). This error signal is then compared with the sawtooth signal to generate the fixed frequency pulse width modulated pulses which drive the output stage. The gain and frequency stability of the loop can be adjusted by an external RC network connected to pin 3. Closing the loop directly gives an output voltage of 5.1V. Higher voltages are obtained by inserting a voltage divider. Output overcurrents at switch on are prevented by the soft start function. The error amplifier output is initially clamped by the external capacitor Css and allowed to rise, linearly, as this capacitor is charged by a constant current source. Output overload protection is provided in the form of a current limiter. The load current is sensed by an internal metal resistor connected to a comparator. When the load current exceeds a preset threshold this comparator sets a flip flop which disables the output stage and discharges the soft start capacitor. A second comparator resets the flip flop when the voltage across the soft start capacitor has fallen to 0.4V. The output stage is thus re-enabled and the output voltage rises under control of the soft start network. If the overload condition is still present the limiter will trigger again when the threshold current is reached. The average short circuit current is limited to a safe value by the dead time introduced by the soft start network. The thermal overload circuit disables circuit operation when the junction temperature reaches about 150°C and has hysteresis to prevent unstable conditions. Figure 1. Soft start waveforms Figure 2. Current limiter waveforms 5/16 L4960 Figure 3. Test and application circuit C6, C7: EKR (ROE) L1 = 150µH at 5A (COGEMA 946042) CORE TYPE: MAGNETICS 58206-A2 MPP N° TURNS 45, WIRE GAUGE: 0.8mm (20 AWG) Figure 4. Quiescent drain current vs. supply voltage (0% duty cycle) 6/16 Figure 5. Quiescent drain current vs. supply voltage (100% duty cycle) Figure 6. Quiescent drain current vs. junction temperature (0% duty cycle) L4960 Figure 7. Quiescent drain current vs. junction temperature (100% duty cycle) Figure 8. Reference voltage (pin 2) vs. Vi Figure 9. Reference voltage versus junction temperature (pin 2) Figure 10. Open loop frequency and phase responde of error amplifier Figure 11. Switching frequency vs. input voltage Figure 12. Switching frequency vs. junction temperature Figure 13. Switching frequency vs. R2 (see test circuit) Figure 14. Line transient response Figure 15. Load transient response 7/16 L4960 Figure 16. Supply voltage ripple rejection vs. frequency Figure 17. Dropout voltage between pin 1 and pin 7 vs. current at pin 7 Figure 18. Dropout voltage between pin 1 and 7 vs. junction temperature Figure 19. Power dissipation derating curve Fi gure 20. Effici ency vs. output current Fi gure 21 . Effi ciency vs. output current F igu re 22. Effi ciency vs. output current 8/16 Fi gure 2 3. Effi ciency vs. output voltage L4960 APPLICATION INFORMATION Figure 24. Typical application circuit C1, C6, C7: EKR (ROE) D1: BYW80 OR 5A SCHOTTKY DIODE SUGGESTED INDUCTOR: L1 = 150µH at 5A CORE TYPE: MAGNETICS 58206 - A2 - MPP N° TURNS: 45, WIRE GAUGE: 0.8mm (20 AWG), COGEMA 946042 U15/GUP15: N° TURNS: 60, WIRE GAUGE: 0.8mm (20 AWG), AIR GAP: 1mm, COGEMA 969051. Figure 25. P.C. board and component layout of the Fig. 24 (1 : 1 scale) Resistor values for standard output voltages Vo 12V 15V 18V 24V R3 4.7KΩ 4.7KΩ 4.7KΩ 4.7KΩ R4 6.2KΩ 9.1KΩ 12KΩ 18KΩ 9/16 L4960 APPLICATION INFORMATION Figure 26. A minimal 5.1V fixed regulator; Very few component are required * COGEMA 946042 (TOROID CORE) 969051 (U15 CORE) ** EKR (ROE) Figure 27. Programmable power supply Vo = 5.1V to 15V Io = 2.5A max Load regulation (1A to 2A) = 10mV (Vo = 5.1V) 10/16 L4960 APPLICATION INFORMATION (continued) Figure 28. Microcomputer supply with + 5.1V, -5V, +12V and -12V outputs 11/16 L4960 APPLICATION INFORMATION (continued) Figure 29. DC-DC converter 5.1V/4A, ± 12V/2.5A; a suggestion how to synchronize a negative output L1, L3 = COGEMA 946042 (969051) L2 = COGEMA 946044 (946045) D1, D2, D3 = BYW80 Figure 30. - In multiple supplies several L4960s can be synchronized as shown 12/16 L4960 APPLICATION INFORMATION (continued) Figure 31. Regulator for distributed supplies MOUNTING INSTRUCTION The power dissipated in the circuit must be removed by adding an external heatsink. Thanks to the Heptawatt package attaching the hetsink is very simple, a screw or a compression spring (clip) being sufficient. Between the heatsink and the package it is better to insert a layer of silicon grease, to optimize the thermal contact, no electrical isolation is needed between the two surfaces. Figure 32. Mounting example 13/16 L4960 DIM. A C D D1 E E1 F F1 G G1 G2 H2 H3 L L1 L2 L3 L4 L5 L6 L7 L9 M M1 V4 Dia MIN. mm TYP. 2.4 1.2 0.35 0.7 0.6 2.34 4.88 7.42 10.05 16.7 21.24 22.27 2.6 15.1 6 2.55 4.83 2.54 5.08 7.62 16.9 14.92 21.54 22.52 2.8 15.5 6.35 0.2 2.8 5.08 3.65 MAX. 4.8 1.37 2.8 1.35 0.55 0.97 0.8 0.9 2.74 5.28 7.82 10.4 10.4 17.1 21.84 22.77 1.29 3 15.8 6.6 inch TYP. MIN. 0.094 0.047 0.014 0.028 0.024 0.095 0.193 0.295 0.396 0.657 0.386 0.877 0.102 0.594 0.236 3.05 0.100 5.33 0.190 40˚ (typ.) 3.85 0.144 0.100 0.200 0.300 0.668 0.587 0.848 0.891 0.110 0.610 0.250 0.008 0.110 0.200 OUTLINE AND MECHANICAL DATA MAX. 0.189 0.054 0.110 0.053 0.022 0.038 0.031 0.035 0.105 0.205 0.307 0.409 0.409 0.673 0.860 0.896 0.051 0.118 0.622 0.260 0.120 0.210 Heptawatt V 0.152 V L V E L1 M1 A M D C D1 H2 L2 L5 L3 F E E1 V4 L9 H3 G H1 G1 G2 Dia. F L4 L7 L6 14/16 H2 F1 HEPTAMEC L4960 mm DIM. MIN. TYP. inch MAX. MIN. TYP. MAX. A 4.8 0.189 C 1.37 0.054 D 2.4 2.8 0.094 0.110 D1 1.2 1.35 0.047 0.053 E 0.35 0.55 0.014 0.022 F 0.6 0.8 0.024 0.031 F1 0.9 0.035 G 2.41 2.54 2.67 0.095 0.100 0.105 G1 4.91 5.08 5.21 0.193 0.200 0.205 G2 7.49 7.62 7.8 0.295 0.300 0.307 H2 H3 10.4 10.05 L 10.4 0.409 0.396 0.409 14.2 0.559 L1 4.4 0.173 L2 15.8 0.622 L3 5.1 0.201 L5 2.6 3 0.102 0.118 L6 15.1 15.8 0.594 0.622 L7 6 6.6 0.236 L9 Dia 4.44 3.65 OUTLINE AND MECHANICAL DATA 0.260 Heptawatt H 0.175 3.85 0.144 0.152 15/16 L4960 Information furnished is believed to be accurate and reliable. However, STMicroelectronics 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. The ST logo is a registered trademark of STMicroelectronics © 2000 STMicroelectronics – Printed in Italy – All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com 16/16