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PDF L4978D Data sheet ( Hoja de datos )
| Número de pieza | L4978D | |
| Descripción | 2A STEP DOWN SWITCHING REGULATOR | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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® L4978
2A STEP DOWN SWITCHING REGULATOR
UP TO 2A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 8V TO
55V
PRECISE 3.3V (±1%) INTERNAL REFER-
ENCE VOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM
3.3V TO 50V
SWITCHING FREQUENCY ADJUSTABLE UP
TO 500KHz
VOLTAGE FEEDFORWARD
ZERO LOAD CURRENT OPERATION
INTERNAL CURRENT LIMITING (PULSE-BY-
PULSE AND HICCUP MODE)
INHIBIT FOR ZERO CURRENT CONSUMP-
TION
PROTECTION AGAINST FEEDBACK DIS-
CONNECTION
THERMAL SHUTDOWN
SOFT START FUNCTION
DESCRIPTION
The L4978 is a step down monolithic power
switching regulator delivering 2A at a voltage be-
tween 3.3V and 50V (selected by a simple exter-
nal divider). Realized in BCD mixed technology,
the device uses an internal power D-MOS transis-
tor (with a typical Rdson of 0.25Ω) to obtain very
high efficency and high switching speed.
TYPICAL APPLICATION CIRCUIT
Minidip
SO16W
ORDERING NUMBERS: L4978 (Minidip)
L4978D (SO16)
A switching frequency up to 500KHz is achiev-
able (the maximum power dissipation of the pack-
ages must be observed).
A wide input voltage range between 8V to 55V
and output voltages regulated from 3.3V to 50V
cover the majority of today’s applications.
Features of this new generations of DC-DC con-
verter include pulse-by-pulse current limit, hiccup
mode for short circuit protection, voltage feedfor-
ward regulation, soft-start, protection against
feedback loop disconnection, inhibit for zero cur-
rent consumption and thermal shutdown.
The device is available in plastic dual in line,
MINIDIP 8 for standard assembly, and SO16W
for SMD assembly.
Vi=8V to 55V
C1
220µF
63V
C7
220nF
R1
20K
C2
2.7nF
5
8
L4978
3
4
27
16
L1
126µH
(77120)
VO=3.3V/2A
C5
100nF
R2
9.1K
C4
22nF
C6
100nF
D1
GI
SB560
C8
330µF
D98IN837A
May 2000
1/12
1 page  
Figure 1. Test and evaluation board circuit.
L4978
Vi=8V to 55V
C1
220µF
63V
C7
220nF
R1
20K
C2
2.7nF
5
L4978
3
27
1
C5
100nF C4
22nF
R2
9.1K
8
4
6
C6
100nF
D1
GI
SB560
L1
126µH
(77120)
C8
330µF
VO=3.3V/2A
R3
R4
C1=220µF/63V EKE
C2=2.7nF
C5=100nF
C6=100nF
C7=220nF/63V
C8=330µF/35V CG Sanyo
L1=126µH KoolMu 77120 - 55 Turns - 0.5mm
R1=20K
R2=9.1K
D1=GI SB560
D98IN834A
VO(V)
3.3
5.1
12
15
18
24
L4978
R3(KΩ)
0
2.7
12
16
20
30
R4(KΩ)
4.7
4.7
4.7
4.7
4.7
Figure 2. PCB and component layout of the figure 1.
5/12
5 Page 
DIM.
MIN.
mm
TYP. MAX. MIN.
inch
TYP. MAX.
A 2.35
2.65 0.093
0.104
A1 0.1
0.3 0.004
0.012
B 0.33
0.51 0.013
0.020
C 0.23
0.32 0.009
0.013
D 10.1
10.5 0.398
0.413
E 7.4
7.6 0.291
0.299
e 1.27
0.050
H 10
10.65 0.394
0.419
h 0.25
0.75 0.010
0.030
L 0.4
1.27 0.016
0.050
K 0° (min.)8° (max.)
L4978
OUTLINE AND
MECHANICAL DATA
SO16 Wide
B
16
1
L
h x 45
A
e K A1 C
H
D
9
E
8
11/12
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet L4978D.PDF ] | |
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