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
µ
F, ESR < 10
Ω
,
R
p
= 1K
Ω
, R
L
= 1K
Ω
, –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
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
∆V
o
Line Regulation V
i
= 6V to 26V ;
I
o
= 5mA
210mV
∆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
= 100µF ;
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 µA
V
RT peak
Power On-Off Reset out Peak
Voltage
1KΩ 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 –0.15
V
V
L4947R:
V
o
@ Reset Out H to
L Transition
4.55 Vo –0.30 V
V
RT (on)
Power ON V
o
Threshold V
o
@ Reset Out L to H
Transition
V
RT (off)
+ 0.05
V
o
–
0.04
V
V
Hyst
Power ON-Off Hysteresis V
RT (on)
–V
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/µA
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
∆V
o
T
L4947 - L4947R
3/6
