L4947 L4947r 5v-0.5a very low drop regulator with reset precise output voltage (5v 4%) over full temperature range (C 40 / 125 c) very low voltage drop (0.75vmax) over full t range output current up to 500ma reset function power-on reset delay pulse de- fined by the external capacitor + 80v load dump protection C 80v load dump protection reverse voltage protection short circuit protection and ther- mal shut-down (with hysteresis) low start up current description the L4947/L4947r is a monolithic integrated cir- cuit in pentawatt package specially designed to provide a stabilized supply voltage for automotive and industrial electronic systems. thanks to its very low voltage drop, in automotive applications the L4947/L4947r can work correctly even during the cranking phase, when the battery voltage could fall as low as 6v. furthermore, it incorpo- rates a complete range of protection circuits against the dangerous overvoltages always pre- sent on the battery rail of the car. the reset func- tion makes the device particularly suited to supply microprocessor based systems : a signal is avail- able (after an externally programmable delay) to reset the microprocessor at power-on phase ; at power-off, this signal becomes low inhibiting the microprocessor. this is advanced information on a new product now in development or undergoing evaluation. details are subject to change withou t notice. june 2000 ? block diagram pentawatt ordering numbers: L4947 L4947r 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 3 0.5 w field decay : 5ms t fall 10ms, r source 3 10 w t r rise time constant = 33ms low energy spike : t rise = 1 m s, t fall = 500 m s, r source 3 10 w f r repetition frequency = 5hz 35 C 18 80 C 80 100 v v v v v v r reset output voltage 35 v t j , t stg junction and storage temperature range C 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 3.5 c/w pin connection (top view) test circuit (*) min. 20 m f, esr < 10 w over full temperature range r p (pull up resistor) and r l (load) are both equal to 1k w . L4947 - L4947r 2/6
functional description the L4947/L4947r is a very low drop 5v/0.5a voltage regulator provided with a reset function and therefore particularly suited to meet the re- quirements of supplying the microprocessor sys- tems used in automotive and industrial applica- tions. the block diagram shows the basic structure of the device : 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. 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 , C40 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 t j = 25 c 4.80 4.90 5.00 5.00 5.20 5.10 v 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 Cv 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 C 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 v r reset output saturation voltage 1.5v < v o < v rt (off) , i r = 1.6ma 3.0v < v o < v rt (off) , i r = 8ma 0.40 0.40 v v i r reset output leakage current v o in regulation, v r = 5v 50 m a v rt peak power on-off reset out peak voltage 1k w reset pull-up to v o , t j = 25 c 0.50 0.80 v v rt (off) power off v o threshold t j = 25 c L4947: v o @ reset out h to l transition 4.70 4.75 vo C0.15 v v L4947r: v o @ reset out h to l transition 4.55 vo C0.30 v v rt (on) power on v o threshold v o @ reset out l to h transition v rt (off) + 0.05 v o C 0.04 v v hyst power on-off hysteresis v rt (on) Cv rt (off) 0.05 v v d delay comparator threshold v d @ reset out l to h transition 3.65 4.00 4.35 v v d @ reset out h to l transition 3.20 3.55 3.90 v v dh delay comparator hysteresis 0.45 v i d delay capacitor charging current v d = 3v, t j = 25 c20/ m a v disch delay capacitor discharge voltage v o < v rt (off) 0.55 1.20 v t d power on reset delay time c d = 100nf, t j = 25 c 102030ms (*) for a dc voltage 26 < v i < 37v the device is not operating d v o t L4947 - L4947r 3/6
the current consumption of the device (quiescent current) is maximum 13ma - 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 reset function supervises the regulator output voltage inhibiting the microprocessor when the device is out of regulation and resetting it at the power-on after a settable delay. the reset is low when the output voltage value is lower than the reset threshold voltage. at the power-on phase the output voltage increases (see fig. 2) and - when it reaches the power-on v o threshold v rt (on) - the reset output becomes high after a de- lay time set by the external capacitor c d . at the power-off the output voltage decreases : at the v rt(off) threshold value (v o -0.15v typ. for L4947 and v o -0.3v typ. for L4947r value) the reset out- put instantaneously goes down (low status) in- hibiting the microprocessor. the typical power on- off hysteresis is 50mv. 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), reverse voltage (C 18v) and short circuit protec- tion, thermal shutdown are the main features that make the L4947/L4947r specially suitable for ap- plications in the automotive enviroment. external compensation since the purpose of a voltage regulator is to sup- ply and load variations, the open loop gain of the regulator 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). figure 2: reset waveforms: (1) without external capacitor c d . (2) with external capacitor c d . L4947 - L4947r 4/6
pentawatt v dim. mm inch min. typ. 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 e1 0.76 1.19 0.030 0.047 f 0.8 1.05 0.031 0.041 f1 1 1.4 0.039 0.055 g 3.2 3.4 3.6 0.126 0.134 0.142 g1 6.6 6.8 7 0.260 0.268 0.276 h2 10.4 0.409 h3 10.05 10.4 0.396 0.409 l 17.55 17.85 18.15 0.691 0.703 0.715 l1 15.55 15.75 15.95 0.612 0.620 0.628 l2 21.2 21.4 21.6 0.831 0.843 0.850 l3 22.3 22.5 22.7 0.878 0.886 0.894 l4 1.29 0.051 l5 2.6 3 0.102 0.118 l6 15.1 15.8 0.594 0.622 l7 6 6.6 0.236 0.260 l9 0.2 0.008 m 4.23 4.5 4.75 0.167 0.177 0.187 m1 3.75 4 4.25 0.148 0.157 0.167 v4 40? (typ.) l l1 a c l5 d1 l2 l3 e m1 m d h3 dia. l7 l6 f1 h2 f gg1 e1 f e l9 v4 r r r resin between leads h1 v3 h2 l8 vv v1 b vv v4 v4 outline and mechanical data L4947 - L4947r 5/6
information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsib ility for the cons equences 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 pu blication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectron ics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicr oelectronics. the st logo is a registered trademark of stmicroelectronics ? 2000 stmicroelectronics C printed in italy C 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 L4947 - L4947r 6/6
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