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
HEPTAWATT
ORDERING NUMBERS: L4960 (Vertical) L4960H (Horizontal)
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.
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
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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 = 0.1s; f = 100KHz Voltage at pin 3 and 6 Voltage at pin 2 Pin 3 sink current Pin 5 source current Power dissipation at Tcase 90C 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
N 1 NAME SUPPLY VOLTAGE FUNCTION Unregulated voltage input. An internal regulator powers the internal logic. 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. A series RC network connected between this terminal and ground determines the regulation loop gain characteristics. Common ground terminal. A parallel RC network connected to this terminal determines the switching frequency. 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. Regulator output.
2
FEEDBACK INPUT
3
FREQUENCY COMPENSATION GROUND OSCILLATOR
4 5
6
SOFT START
7
OUTPUT
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L4960
THERMAL DATA
Symbol Rth j-case Rth j-amb Thermal resistance junction-case Thermal resistance junction-ambient Parameter max max Value 4 50 Unit C/W 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
DYNAMIC CHARACTERISTICS
Vo Vi Vo Vo Vref Vref T Vd Iom I7L ISH Output voltage range Input voltage range Line regulation Load regulation Internal reference voltage (pin 2) Average temperature coefficient of refer voltage Dropout voltage Maximum operating load current Current limiting threshold (pin 7) Input average current Efficiency Vi = 46V Vo = Vref to 36V Vi = 10V to 40V Vo = Vref Vi = 9V to 46V Io = 1A Io = 2.5A Vo = Vref Io = 1A Vref 9 15 10 5 5.1 40 46 50 30 5.2 V V mV mV V
Io = 0.5A to 2A Io = 1A
Tj = 0C to 125C Io = 1A Io = 2A Vi = 9V to 46V Vo = Vref to 36V Vi = 9V to 46V Vo = Vref to 36V Vi = 46V; f = 100KHz Io = 2A output short-circuit Vo = Vref Vo = 12V 50 Io = 1A 85 Vi = 9V to 46V 2.5 3
0.4
mV/C
1.4
3
V A
4.5
A
30 75 85 56
60
mA % % dB
SVR
Supply voltage ripple rejection
Vi = 2Vrms fripple = 100Hz Vo = Vref
f f Vi f Tj fmax Tsd
Switching frequency Voltage stability of switching frequency Temperature stability of switching frequency Maximum operating switching frequency Thermal shutdown junction temperature
100 0.5
115
KHz %
Tj = 0C to 125C
1
%
Vo = Vref
Io = 2A
120
150
KHz C
150
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L4960
ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Test Conditions Min. Typ. Max. Unit
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 15 20 1 mA mA 30 40 mA
SOFT START
I6SO I6SI Source current Sink current 100 50 140 70 180 120 A A
ERROR AMPLIFIER
V3H V3L I3SI -I3SO I2 Gv High level output voltage Low level output voltage Sink output current Source output current Input bias current DC open loop gain V2 = 4.7V V2 = 5.3V V2 = 5.3V V2 = 4.7V V2 = 5.2V V3 = 1V to 3V 46 I3 = 100A I3 = 100A 100 100 150 150 2 55 10 3.5 0.5 V V A A A dB
OSCILLATOR
-I5 Oscillator source current 5 mA
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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 150C and has hysteresis to prevent unstable conditions.
Figure 1. Soft start waveforms
Figure 2. Current limiter waveforms
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L4960
Figure 3. Test and application circuit
C6, C7: EKR (ROE) L1 = 150H at 5A (COGEMA 946042) CORE TYPE: MAGNETICS 58206-A2 MPP N TURNS 45, WIRE GAUGE: 0.8mm (20 AWG)
F i g u r e 4. Quiescent drain current vs. supply voltage (0% duty cycle)
F i g u r e 5. Quiescent drain c u rr e n t vs. supply voltage (100% duty cycle)
F i g u r e 6. Quiescent drain c u r r e n t vs. junction temperature (0% duty cycle)
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L4960
Figure 7. Quiescent drain c u r r e n t vs. junction temperature (100% duty cycle) Figure 8. Reference voltage (pin 2) vs. Vi Figure 9. Reference voltage ve rsus junction temperature (p in 2)
F i g u r e 10. Open loop frequency and phase responde of error amplifier
F i g u r e 11. Switching frequency vs. input voltage
F i g u r e 12. Switching freq u e n c y vs. junction temperature
F i g u r e 13. Switching frequency vs. R2 (see test circuit)
F i g u r e 14. Line transient response
F i g u r e 15. Load transient response
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L4960
F i g u r e 16. Supply voltage ripple rejection vs. frequency F i g u re 17. Dropout voltage between pin 1 and pin 7 vs. current at pin 7 F i g ur e 18. Dropout voltage b e t w e e n pin 1 and 7 vs. junction temperature
Figure 19. Power dissipation derating curve
F i g u r e 20. Effici e n c y vs. output current
F i g u r e 21 . Effi c i e n c y vs. output current
F i g u r e 22. Effi c i e n c y vs. output current
F i g u r e 2 3 . Effi c i e n c y vs. output voltage
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L4960
APPLICATION INFORMATION
Figure 24. Typical application circuit
C1, C6, C7: EKR (ROE) D1: BYW80 OR 5A SCHOTTKY DIODE SUGGESTED INDUCTOR: L1 = 150H 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 4.7K 4.7K 4.7K 4.7K R4 6.2K 9.1K 12K 18K
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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)
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L4960
APPLICATION INFORMATION (continued) Figure 28. Microcomputer supply with + 5.1V, -5V, +12V and -12V outputs
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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
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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
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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 mm TYP. inch TYP.
MIN.
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 3.65 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
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
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 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
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 0.152
OUTLINE AND MECHANICAL DATA
3.05 0.100 5.33 0.190 40 (typ.) 3.85 0.144
Heptawatt V
L E L1 M1 A C D1 L2 L5 L3
E E1 F
V
V
D
M H2
V4 L9
H3
H1 Dia.
G
G1
G2
F L7 L6 L4 H2 F1
HEPTAMEC
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L4960
mm MIN. A C D D1 E F F1 G G1 G2 H2 H3 L L1 L2 L3 L5 L6 L7 L9 Dia 3.65 2.6 15.1 6 4.44 3.85 0.144 10.05 14.2 4.4 15.8 5.1 3 15.8 6.6 0.102 0.594 0.236 0.175 0.152 2.41 4.91 7.49 2.54 5.08 7.62 2.4 1.2 0.35 0.6 TYP. MAX. 4.8 1.37 2.8 1.35 0.55 0.8 0.9 2.67 5.21 7.8 10.4 10.4 0.396 0.559 0.173 0.622 0.201 0.118 0.622 0.260 0.095 0.193 0.295 0.100 0.200 0.300 0.094 0.047 0.014 0.024 MIN. inch TYP. MAX. 0.189 0.054 0.110 0.053 0.022 0.031 0.035 0.105 0.205 0.307 0.409 0.409
DIM.
OUTLINE AND MECHANICAL DATA
Heptawatt H
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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
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