L4945
5V VERY LOW DROP VOLTAGE REGULATOR
5V 4% PRECISE OUTPUT VOLTAGE OVER FULL TEMPERATURE RANGE ( 40 / 125 C) VERY LOW VOLTAGE DROP (0.75Vmax) OVER FULL TEMPERATURE RANGE OUTPUT CURRENT UP TO 500mA OVERVOLTAGE AND REVERSE VOLTAGE PROTECTIONS REVERSE VOLTAGE PROTECTION SHORT CIRCUIT PROTECTION AND THERMAL SHUT-DOWN (with hysteresis) LOW START UP CURRENT DESCRIPTION The L4945 is a monolithic integrated circuit in Versawatt package specially designed to provide a stabilized supply voltage for automotive and industrial electronic systems. Thanks to their very low voltage drop, in automotive applications the devices can work correctly even during the crankBLOCK DIAGRAM
TO220 ORDERING NUMBER: L4945
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ing phase, when the battery voltage could fall as low as 6V. Furthermore, they incorporate a complete range of protection circuits against the dangerous overvoltages always present on the battery rail of the car.
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This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
March 1999
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L4945
ABSOLUTE MAXIMUM RATINGS
Symbol Vi Parameter DC Input Voltage DC Reverse Input Voltage Transient Input Overvoltages : Load Dump : 5ms trise 10ms f Fall Time Constant = 100ms RSOURCE 0.5 Field Decay : 5ms tfall 10ms, RSOURCE 10 r Rise Time Constant = 33ms Low Energy Spike : trise = 1s, tfall = 500s, RSOURCE 10 fr Repetition Frequency = 5Hz Junction Temperature Range Operating Temperature Range Storage Temperature Range Value 35 18 80 Unit V V V
80 100
V V
TJ TOP Tstg
40 to 150 40 to 125 55 to 150
C C C
Note: The circuit is ESD protected according to MIL-STD-883C.
PIN CONNECTION (Top view)
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THERMAL DATA
Symbol Rth j-case Parameter Thermal Resistance Junction-case Max Value 3 Unit C/W
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TEST CIRCUIT
ELECTRICAL CHARACTERISTICS (refer to the test circuit, Vi = 14. 4V, Co = 47F, ESR < 10, Rp = 1K, RL = 1K, 40C TJ 125C, unless otherwise specified)
Symbol Vo Parameter Output Voltage Test Conditions Io = 0mA to 500mA Over Full T Range Tj = 25C Vi Vo Vo Vi Vo Iq Vo Operating Input Voltage Line Regulation Load Regulation Dropout Voltage Quiescent Current Io = 0mA to (*) 500mA Vi = 6V to 26V ; Io = 5mA Io = 5mA to 500mA Io = 500mA, TJ = 25C Over Full T Range Min. 4.80 4.90 6 Typ. 5.00 5.00 Max. 5.20 Unit V V
Io = 0mA, TJ = 25C Io = 0mA Over Full T Io = 500mA Over Full T
T
SVR
Temperature Output Voltage Drift Supply Volt. Rej.
Isc
Output Short Circuit Current
(*) For a DC voltage 26 < Vi < 37V the device is not operating
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FUNCTIONAL DESCRIPTION The block diagram shows the basic structure of the devices : the reference, the error amplifier, the driver, the power PNP, the protection and reset functions. The power stage is a Lateral PNP transistor which allows a very low dropout voltage (typ. 400mV at TJ = 25C, max. 750mV over the full temperature range @ IO = 500mA). The typical curve of the dropout voltage as a function of the junction temperature is shown in Fig. 1 : that is the worst case, where IO = 500mA. The current consumption of the devices (quiescent current) are maximum 10mA - over full T -
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2 15 0.40 5 6.5 110 0.5
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V mV mV V V mA mA mA mV/C dB
10 60 0.55 0.75 10 13 180
Io = 350mA ; f = 120Hz Co = 100F ; Vi = 12V 5Vpp
50
60
0.50
0.80
1.50
A
when no load current is required. The internal antisaturation circuit allows a drastic reduction in the current peak which takes place during the start up. The three gain stages (operational amplifier, driver and power PNP) require the external capacitor (Comin = 20F) to guarantee the global stability of the system. Load dump and field decay protections ( 80V, t = 300ms), reverse voltage ( 18V) and short circuit protection, thermal shutdown are the main features that make the devices specially suitable for applications in the automotive enviroment.
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Figure 1: Typical Dropout Voltage vs. Tj (Io = 500mA). ous poles present in the loop. To avoid this instability dominant pole compensation is used to reduce phase shift due to other poles at the unity gain frequency. The lower the frequency of these others poles at the unity gain frequency. The lower the frequency of these other poles, the greater must be capacitor esed to create the dominant pole for the same DC gain. Where the output transistor is a lateral PNP type there is a pole in the regulation loop at a frequencybtoo low to be compensated by a capacitor which can be integrated. An external compensation is therefore necessary so a very high value capacitor must be connected from the output to ground. The paeassitic equivalent series resistance of the capacitor used adds a zero to the regulation loop. This zero may compromise the stability of the system since its effect tends to cancel the effect of the pole added. In regulators this ESR must be less than 3 and the minimum capacitor value is 47F.
EXTERNAL COMPENSATION Since the purpose of a voltage regulator is to supply and load variations, the open loop gain of the regulators must be very high at low frequencies. This may cause instability as a result of the vari-
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mm MIN. A C D E F F1 F2 G G1 H2 L2 L4 L5 L6 L7 L9 M Dia 3.75 13.0 2.65 15.25 6.20 3.50 2.6 3.85 0.147 4.40 1.23 2.40 0.49 0.61 1.14 1.14 4.95 2.40 10.0 16.4 14.0 2.95 15.75 6.60 3.93 0.511 0.104 0.600 0.244 0.137 0.102 0.151 TYP. MAX. 4.60 1.32 2.72 0.70 0.88 1.70 1.70 5.15 2.70 10.4 MIN. 0.173 0.048 0.094 0.019 0.024 0.044 0.044 0.194 0.094 0.393 0.645 0.551 0.116 0.620 0.260 0.154 inch TYP. MAX. 0.181 0.051 0.107 0.027 0.034 0.067 0.067 0.203 0.106 0.409
DIM.
OUTLINE AND MECHANICAL DATA
Versawatt (TO220)
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TO220MEC
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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 1999 STMicroelectronics Printed in Italy All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com
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