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. ..
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L4947PD
5V-0.5A VERY LOW DROP REGULATOR WITH RESET
L4947PD5V-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 L4947PD is a monolithic integrated circuit in
HiPSO package specially designed to provide a
stabilized supply voltage for automotive and in-
dustrial electronic systems. Thanks to its very low
voltage drop, in automotive applications the
L4947PD can work correctly even during the
cranking phase, when the battery voltage could
fall as low as 6V. Furthermore, it incorporates a
complete range of protection circuits against the
dangerous overvoltages always present on the
battery rail of the car. The reset function makes
the device particularly suited to supply microproc-
essor based systems : a signal is available (after
an externally programmable delay) to reset the
microprocessor at power-on phase ; at power-off,
this signal becomes low inhibiting the microproc-
essor.
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Note: The circuit is ESD protected according to MIL-STD-883C.
THERMAL DATA
PIN CONNECTION (Top view)
TEST CIRCUIT
L4947PD2/6
FUNCTIONAL DESCRIPTIONThe L4947PD is a very low drop 5V/0.5A voltage
regulator provided with a reset function and there-
fore particularly suited to meet the requirements
of supplying the microprocessor systems used in
automotive and industrial applications.
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.
The current consumption of the device (quiescent
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
L4947PD3/6
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. value) the
reset output instantaneously goes down (LOW
status) inhibiting 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 L4947PD specially suitable for applica-
tions 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.
L4947PD4/6
(1) "D and F" do not include mold flash or protrusions.
- Mold flash or protrusions shall not exceed 0.15 mm (0.006").
- Critical dimensions: "E", "G" and "a3"
L4947PD5/6
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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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L4947PD6/6
