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 ther- mal 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 in- dustrial electronic systems. thanks to their very low voltage drop, in automotive applications the devices can work correctly even during the crank- ing phase, when the battery voltage could fall as low as 6v. furthermore, they incorporate a com- plete range of protection circuits against the dan- gerous overvoltages always present on the bat- tery rail of the car. this is advanced information on a new product now in development or undergoing evaluation. details are subject to change without notice. march 1999 ? block diagram to220 ordering number: L4945 1/6
absolute maximum ratings symbol parameter value unit v i dc input voltage dc reverse input voltage transient input overvoltages : load dump : 5ms t rise 10ms t f fall time constant = 100ms r source 0.5 w field decay : 5ms t fall 10ms, r source 10 w t r rise time constant = 33ms low energy spike : t rise =1 m s, t fall = 500 m s, r source 10 w f r repetition frequency = 5hz 35 18 80 80 100 v v v v v t j junction temperature range 40 to 150 c t op operating temperature range 40 to 125 c t stg storage temperature range 55 to 150 c note: the circuit is esd protected according to mil-std-883c. thermal data symbol parameter value unit r th j-case thermal resistance junction-case max 3 c/w pin connection (top view) L4945 2/6
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 t j =25 c, max. 750mv over the full temperature range @ i o = 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 i o = 500ma. the current consumption of the devices (quies- cent current) are maximum 10ma - over full t - 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 ca- pacitor (c omin =20 m f) 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 fea- tures that make the devices specially suitable for applications in the automotive enviroment. electrical characteristics (refer to the test circuit, v i = 14. 4v, c o =47 m f, esr < 10 w , r p =1k w ,r l =1k w , 40 c t j 125 c, unless otherwise specified) symbol parameter test conditions min. typ. max. unit v o output voltage i o = 0ma to 500ma over full t range 4.80 5.00 5.20 v t j =25 c 4.90 5.00 5.10 v v i operating input voltage i o = 0ma to (*) 500ma 6 26 v d v o line regulation v i = 6v to 26v ; i o = 5ma 210mv d v o load regulation i o = 5ma to 500ma 15 60 mv v i v o dropout voltage i o = 500ma, t j =25 c over full t range 0.40 0.55 0.75 v v i q quiescent current i o = 0ma, t j =25 c i o = 0ma over full t i o = 500ma over full t 5 6.5 110 10 13 180 ma ma ma temperature output voltage drift 0.5 mv/ c svr supply volt. rej. i o = 350ma ; f = 120hz c o = 100 m f; v i = 12v 5v pp 50 60 db i sc output short circuit current 0.50 0.80 1.50 a (*) for a dc voltage 26 < v i < 37v the device is not operating d v o t test circuit L4945 3/6
external compensation since the purpose of a voltage regulator is to sup- ply 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- ous poles present in the loop. to avoid this insta- bility dominant pole compensation is used to re- duce 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 fre- quencybtoo low to be compensated by a capaci- tor which can be integrated. an external compen- sation 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 w and the minimum capacitor value is 47 m f. figure 1: typical dropout voltage vs. t j (i o = 500ma). L4945 4/6
versawatt (to220) dim. mm inch min. typ. max. min. typ. max. a 4.40 4.60 0.173 0.181 c 1.23 1.32 0.048 0.051 d 2.40 2.72 0.094 0.107 e 0.49 0.70 0.019 0.027 f 0.61 0.88 0.024 0.034 f1 1.14 1.70 0.044 0.067 f2 1.14 1.70 0.044 0.067 g 4.95 5.15 0.194 0.203 g1 2.40 2.70 0.094 0.106 h2 10.0 10.4 0.393 0.409 l2 16.4 0.645 l4 13.0 14.0 0.511 0.551 l5 2.65 2.95 0.104 0.116 l6 15.25 15.75 0.600 0.620 l7 6.20 6.60 0.244 0.260 l9 3.50 3.93 0.137 0.154 m 2.6 0.102 dia 3.75 3.85 0.147 0.151 m to220mec outline and mechanical data L4945 5/6
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 L4945 6/6
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