L4947L ,5V-0.5A VERY LOW DROP REGULATOR WITH RESETABSOLUTE MAXIMUM RATINGSSymbol Parameter Value UnitV DC Input Voltage 35 ViDC Reverse Input Voltage ..
L4947PD ,5V-0.5A VERY LOW DROP REGULATOR WITH RESETABSOLUTE MAXIMUM RATINGSSymbol Parameter Value UnitV DC Input Voltage 35 ViDC Reverse Input Voltage ..
L4947PD ,5V-0.5A VERY LOW DROP REGULATOR WITH RESETELECTRICAL CHARACTERISTICS (refer to the test circuit, V = 14. 4V, C = 47μF, ESR < 10Ω,i oR = 1K ..
L4947R ,5V-0.5A VERY LOW DROP REGULATOR WITH RESETL4947L4947R®5V-0.5A VERY LOW DROP REGULATOR WITH RESETPRECISE OUTPUT VOLTAGE (5V ± 4%)OVER FULL TEM ..
L4949 ,MULTIFUNCTION VERY LOW DROP VOLTAGE REGULATOROrder this document from L4949/D* * ** ** * MULTIFUNCTIONThe L4949 is a monolithic integrated 5. ..
L4949D ,MULTIFUNCTION VERY LOW DROPOUT VOLTAGE REGULATORMAXIMUM RATINGSRating Symbol Value UnitDC Operating Supply Voltage V 28 VCCTransient Supply Voltage ..
LBAT54HT1G , Schottky Barrier Diodes Device Marking: JV
LBAT54LT1G , Dual Series Schottky Barrier Diodes Extremely Fast Switching Speed
LBAV99WT1G , Dual Serise Switching Diodes
LBAV99WT1G , Dual Serise Switching Diodes
LBAW56LT1G , Monolithic Dual Switching Diode Common Anode
LBAW56LT1G , Monolithic Dual Switching Diode Common Anode
L4947H-L4947L
5V-0.5A VERY LOW DROP REGULATOR WITH RESET
L4947
L4947R5V-0.5A VERY LOW DROP REGULATOR WITH RESET
PRECISE OUTPUT VOLTAGE (5V ± 4%)
OVER FULL TEMPERATURE RANGE
(– 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
– 80V LOAD DUMP PROTECTION
REVERSE VOLTAGE PROTECTION
SHORT CIRCUIT PROTECTION AND THER-
MAL SHUT-DOWN (with hysteresis)
LOW START UP CURRENT
DESCRIPTIONThe 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.
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Note: The circuit is ESD protected according to MIL-STD-883C.
THERMAL DATA
PIN CONNECTION (Top view)
TEST CIRCUIT
L4947 - L4947R2/6
FUNCTIONAL DESCRIPTIONThe 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 TJ = 25°C, 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.
ELECTRICAL CHARACTERISTICS (refer to the test circuit, Vi = 14. 4V, Co = 47μF, ESR < 10Ω,Rp = 1KΩ, RL = 1KΩ, –40°C ≤ TJ ≤ 125°C, unless otherwise specified)
(*) For a DC voltage 26 < Vi < 37V the device is not operating
L4947 - L4947R3/6
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 VO threshold VRT
(On) - the reset output becomes HIGH after a de-
lay time set by the external capacitor Cd. At the
power-off the output voltage decreases : at the
VRT(Off) threshold value (VO-0.15V typ. for L4947
and VO-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 (Comin = 20μF) to guarantee the global
stability of the system.
Load dump and field decay protections (± 80V),
reverse voltage (– 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 3Ω and the minimum capacitor value is
47μF.
Figure 1: Typical Dropout Voltage vs. Tj(Io = 500mA).
Figure 2: Reset Waveforms:(1) Without External Capacitor Cd.
(2) With External Capacitor Cd.
L4947 - L4947R4/6
L4947 - L4947R5/6
. 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.
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L4947 - L4947R6/6
