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PDF L4909 Data sheet ( Hoja de datos )
| Número de pieza | L4909 | |
| Descripción | EXTERNALLY ADJUSTABLE MULTIFUNCTION REGULATOR | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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L4909
EXTERNALLY ADJUSTABLE MULTIFUNCTION REGULATOR
s 3 OUTPUTS
- Vo1 : output voltage variable from 5 to 12 V;
limit current : 1.2 A.
- Vo2 : output voltage variable from 5 to 12 V;
limit current : 1.2 A.
- Vo3 : output voltage variable from 5 to 12 V;
limit current : 1.2 A.
s ENABLE INPUT FOR EACH REGULATOR
s FEEDBACK INPUT FOR EACH REGULATOR
s SHORT CIRCUIT PROTECTION TO GROUND
s OVERCURRENT WARNING
s DRIVER FOR EXTERNAL SCR (CROWBAR
PROTECTION)
s THERMAL SHUTDOWN
DESCRIPTION
It is a monolithic Multifunction Voltage Regulator; it
contains 3 regulators, (REG1, REG2, REG3) each
one with an enable input and a feedback input, to al-
low the voltage setting via external resistive divider.
BLOCK DIAGRAM
MULTIWATT 15
Each regulator is current limited and furthermore an
OR-ed warning signal is output (open collector, ac-
tive low output) when the current in a regulator goes
above an over-current threshold (1 A typ for any reg-
ulator).
When one output voltage is higher than 20% typ of its
nominal value (for instance in case of input-to-output
short circuit), the crowbar output pin is activated, trig-
gering an external SCR (connected between input
and ground) that blows the input line fuse.
EN1
EN2
EN3
6
7
9
+
THERMAL
SHUTDOWN
ENABLE
CONTROL
REFERENCE
GENERATOR
REF
REF+20%
REG1
REG2
REG3
+
-
+
5
OC
4
TRIG
8
GND
OVER
CURRENT
CHECK
-
+
-
+
May 2000
+
REG1
-
+
REG2
-
+
REG3
-
+
3,13
+
VINA, VINB
2
1
+
VO1
FB1
14
15
+
VO2
FB2
11
VO3
10
FB3
D00AU1171
1/7
1 page  
L4909
The current protection is a function of the Vce, i.e. the drop between input and output voltages (Vin-Vo). The
shape of that relationship is shown in following figure 1.
Figure 1.
Figure 2. REGULATOR TYPICAL APPLICATION
FROM
RECTIFIER
ULTRAFAST FUSE
+5V
330nF
4.7K
PULL-UP
RESISTOR
SCR
VINA
(*)EN1
3
6
VINB
13
2
(*)EN2
7
14
11
(*)EN3
9
OC
5
1
15
TRIG
4
12
8
GND
VO1
VO2
VO3
FB1
FB2
FB3
RB3 RB2 RB1
100µF
RA3 RA2 RA1
(*) It is possible to enable the regulators connecting the ENx pins to Vin through a 25KΩ
Suggested value for RAx is 1.2KΩ
The value of RBx must be choosen, depending on the desired output voltage Vox? following the formula:
Vox
RBx = RAx 1.27 -1
100µF
100nF
D00AU1154
100µF
100nF
100nF
5/7
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet L4909.PDF ] | |
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