ChipFind - документация

Электронный компонент: L4947

Скачать:  PDF   ZIP
L4947
L4947R
5V-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
DESCRIPTION
The L4947/L494 7R 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 without 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
f
Fall Time Constant = 100ms
R
SOURCE
0.5
Field Decay :
5ms
t
fall
10ms, R
SOURCE
10
r
Rise Time Constant = 33ms
Low Energy Spike :
t
rise
= 1
s, t
fall
= 500
s, R
SOURCE
10
f
r
Repetition Frequency = 5Hz
35
18
80
80
100
V
V
V
V
V
V
R
Reset Output Voltage
35
V
T
J
, T
stg
Junction and 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
3.5
C/W
PIN CONNECTION (Top view)
TEST CIRCUIT
(*) Min. 20
F, ESR < 10
over full temperature range R
P
(pull up resistor) and R
L
(load) are both equal to 1K
.
L4947 - L4947R
2/6
FUNCTIONAL DESCRIPTION
The L4947/L494 7R 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
F, ESR < 10
,
R
p
= 1K
, R
L
= 1K
, 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
2
10
mV
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
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
A
V
RT peak
Power On-Off Reset out Peak
Voltage
1K
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
Vo0.15
V
V
L4947R: V
o
@ Reset Out H to
L Transition
4.55
Vo0.30
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
C
20
/
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
10
20
30
ms
(*) For a DC voltage 26 < V
i
< 37V the device is not operating
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
F) 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/L4947Rspecially 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
and the minimum capacitor value is
47
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
G G1
E1
F
E
L9
V4
R
R
R
RESIN BETWEEN
LEADS
H1
V3
H2
L8
V
V
V1
B
V
V
V4
V4
OUTLINE AND
MECHANICAL DATA
L4947 - L4947R
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 parti es 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
2000 STMicroelectronics Printed in Italy 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