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L5972D
May 2003
s
2A INTERNAL SWITCH
s
OPERATING INPUT VOLTAGE FROM 4.4V
TO 36V
s
OUTPUT VOLTAGE ADJUSTABLE FROM
1.235V TO 35V
s
LOW DROPOUT OPERATION: 100% DUTY
CYCLE
s
250KHz INTERNALLY FIXED FREQUENCY
s
VOLTAGE FEEDFORWARD
s
ZERO LOAD CURRENT OPERATION
s
INTERNAL CURRENT LIMITING
s
PROTECTION AGAINST FEEDBACK
DISCONNECTION
s
THERMAL SHUTDOWN
APPLICATIONS:
s
CONSUMER: STB, DVD, TV, VCR,CAR
RADIO, LCD MONITORS
s
NETWORKING: XDSL, MODEMS,DC-DC
MODULES
s
COMPUTER: PRINTERS, AUDIO/GRAPHIC
CARDS, OPTICAL STORAGE, HARD DISK
DRIVE
s
INDUSTRIAL: CHARGERS, CAR BATTERY
DC-DC CONVERTERS
DESCRIPTION
The L5972D is a step down monolithic power switch-
ing regulator with a minimum switch current limit of
2A so it is able to deliver more than 1.5A DC current
to the load depending on the application conditions.
The output voltage can be set from 1.235V to 35V.
The device uses an internal P-Channel D-MOS tran-
sistor (with a typical Rdson of 250m
) as switching
element to minimize the size of the external compo-
nents.
An internal oscillator fixes the switching frequency at
250KHz.
Having a minimum input voltage of 4.4V only, it is
particularly suitable for 5V bus, available in all com-
puter related applications.
Pulse by pulse current limit with the internal frequen-
cy modulation offers an effective constant current
short circuit protection.
SO8 (4+2+2)
ORDERING NUMBERS: L5972D (SO8)
L5972D013TR (Tape & Reel)
2A SWITCH STEP DOWN SWITCHING REGULATOR
TEST APPLICATION CIRCUIT
D03IN1436
8
2
4
5
1
7
L5972D
C1
10
F
35V
CERAMIC
C2
100
F
10V
VOUT=3.3V
VIN = 4.4V to 35V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
L1 33
H
6
D1
STPS2L40U
COMP
VCC
OUT
FB
GND
L5972D
2/10
PIN CONNECTION
PIN DESCRIPTION
THERMAL DATA
(*) Package mounted on board (4cm
2
ground-plane)
ABSOLUTE MAXIMUM RATINGS
N
Pin
Function
1
OUT
Regulator Output.
2,3,6,7
GND
Ground.
4
COMP
E/A output for frequency compensation.
5
FB
Feedback input. Connecting directly to this pin results in an output voltage of 1.23V. An external
resistive divider is required for higher output voltages.
8
VCC
Unregulated DC input voltage.
Symbol
Parameter
Value
Unit
R
th (j-amb)
Thermal Resistance Junction to ambient
Max.
65 (*)
C/W
Symbol
Parameter
Value
Unit
V
8
Input Voltage
40
V
V
1
Out pin DC voltage
Out pin peak voltage at
t = 0.1
s
-1 to 40
-5 to 40
V
V
I
1
Maximum output current
int. limit.
V
4
, V
5
Analog pins
4
V
P
tot
Power dissipation at Tamb
70C
1.2
W
T
j
Operating junction temperature range
-40 to 150
C
T
stg
Storage temperature range
-55 to 150
C
OUT
GND
GND
COMP
1
3
2
4
VCC
GND
GND
FB
8
7
6
5
D02IN1367
3/10
L5972D
ELECTRICAL CHARACTERISTICS (T
j
= 25C, V
CC
= 12V, unless otherwise specified.)
(*) Specification Referred to Tj from -40 to 125C.
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
V
CC
Operating input voltage range
V
o
= 1.235V; I
o
= 1.5A
*
4.4
36
V
V
d
Dropout voltage
V
CC
= 4.4V; I
o
= 1.5A
*
0.375
0.75
V
I
l
Maximum limiting current
V
CC
= 4.4V to 36V
*
2
2.5
3
A
f
s
Switching frequency
*
212
250
280
KHz
225
250
275
KHz
Duty cycle
0
100
%
DYNAMIC CHARACTERISTICS (see test circuit ).
V
5
Voltage feedback
4.4V < V
CC
< 36V,
20mA < I
O
< 1.5A
1.220
1.235
1.25
V
*
1.198
1.235
1.272
V
h
Efficiency
V
O
= 5V, V
CC
= 12V
90
%
DC CHARACTERISTICS
I
qop
Total operating quiescent current
*
3
5
mA
I
q
Quiescent current
Duty Cycle = 0; V
FB
= 1.5V
2.5
mA
ERROR AMPLIFIER
V
OH
High level output voltage
VFB = 1V
3.5
V
V
OL
Low level output voltage
VFB = 1.5V
0.4
V
I
o source
Source output current
V
COMP
= 1.9V; V
FB
= 1V
200
300
A
I
o sink
Sink output current
V
COMP
= 1.9V; V
FB
= 1.5V
1
1.5
mA
I
b
Source bias current
2.5
4
A
DC open loop gain
R
L
=
50
65
dB
gm
Transconductance
I
comp
= -0.1mA to 0.1mA
V
COMP
= 1.9V
2.3
mS
L5972D
4/10
Figure 1. Output Voltage vs. Junction
Temperature
Figure 2. Line Regulation
Figure 3. Output Voltage vs. Junction
Temperature
Figure 4. Quiescent Current vs. Junction
Figure 5. Shutdown Current vs.Junction
Temperature
Figure 6. Switching Frequency vs.Junction
Temperature
3.276
3.28
3.284
3.288
3.292
3.296
3.3
3.304
3.308
3.312
0
0.5
1
1.5
Io (A)
Vo (V)
Tj = 125C
Tj = 25C
Vcc = 12V
Vo = 3.3V
3.276
3.28
3.284
3.288
3.292
3.296
3.3
3.304
3.308
3.312
0
10
20
30
40
Vcc (V)
Tj = 125C
Tj = 25C
Vcc = 12V
Vo = 3.3V
Vo (V)
Tj (C)
Vcc=12V
1.2
1.21
1.22
1.23
1.24
1.25
-50
0
50
100
150
Vo (V)
Vcc = 12V
1.2
1.4
1.6
1.8
2
-50
0
50
100
150
Tj (C)
Iq (mA)
Vcc = 12V
DC = 0%
30
40
50
60
70
-50
0
50
100
150
Ishd (
A)
Vcc = 12V
Tj (C)
1.2
1.4
1.6
1.8
2
-50
0
50
100
150
Tj (C)
Iq (mA)
Vcc = 12V
DC = 0%
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L5972D
APPLICATION CIRCUIT
In figure 7 is shown the demo board application circuit for the device in SMD version, where the input supply
voltage, Vcc, can range from 4.4V to 25V due to the rated voltage of the input capacitor and the output voltage
is adjustable from 1.235V to V
cc
.
Figure 7. Demo board Application Circuit
Table 1. Component List
Reference
Part Number
Description
Manufacturer
C1
10
F, 25V
TOKIN
C2
POSCAP 10TPB100M
100
F, 10V
Sanyo
C3
C1206C221J5GAC
220pF, 5%, 50V
KEMET
C4
C1206C223K5RAC
22nF, 10%, 50V
KEMET
R1
5.6K, 1%, 0.1W 0603
Neohm
R2
3.3K, 1%, 0.1W 0603
Neohm
R3
4.7K, 1%, 0.1W 0603
Neohm
D1
STPS2L25U
2A, 25V
ST
L1
DO3316P-333
33
H, 2.1A
COILCRAFT
D03IN1438
8
2
4
5
1
7
L5972D
C1
10
F
25V
CERAMIC
C2
100
F
10V
VOUT=3.3V
VIN = 4.4V to 25V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
L1 33
H
6
D1
STPS2L25U
COMP
VCC
OUT
FB
GND
L5972D
6/10
Figure 8. PCB layout (component side)
Figure 9. PCB layout (bottom side)
Figure 10. PCB layout (front side)
Sideways two graphs show the Tj versus output current in different conditions of the input and output voltage.
42mm
34mm
7/10
L5972D
Figure 11. Junction Temperature vs. Output
Current
Figure 12. Junction Temperature vs. Output
Current
Figure 13. Efficiency vs. Output Current
Figure 14. Efficiency vs. Output Current
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Io(A)
TJ(C)
Vin=5V
Tamb.=25
C
Vo=1.8V
Vo=2.5V
Vo=3.3V
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Io(A)
TJ(C)
Vo=2.5V
V o=3.3V
Vo=5V
Vin=12V
Tamb= 25C
67
69
71
73
75
77
79
81
83
85
87
89
91
93
95
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
Io (A)
Ef
f
i
ci
en
cy (
%
)
Vo=1.8V
Vo=2.5V
Vo=3.3V
Vcc=5V
Vo=1.8V
Vo=2.5V
Vo=3.3V
70
72
74
76
78
80
82
84
86
88
90
92
94
96
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
Io (A)
Effi
c
i
e
n
c
y
(%
)
Vin=12V
Vo=2.5V
Vo=3.3V
Vo=5V
Vin=12V
Vo=2.5V
Vo=3.3V
Vo=5V
L5972D
8/10
APPLICATION IDEAS
Figure 15. Positive Buck-Boost regulator
Figure 16. Buck-Boost regulator
Figure 17. Dual output voltage with auxiliary winding
VIN=5V
C1
10uF
10V
Ceramic
D1
STPS2L25U
Vcc
COMP
GND
OUT
FB
L5972D
1
3
7
5
6
4
8
2
R3
4.7k
L1
33uH
24k
2.7k
C3
22nF
C4
100uF
16V
VOUT=12V/0.45A
C2
220pF
D2
STPS2L25U
M1
STN4NE03L
VIN=5V
C1
10uF
10V
Ceramic
D1
STPS2L25U
Vcc
COMP
GND
OUT
FB
L5972D
1
3
7
5
6
4
8
2
R3
4.7k
L1
33uH
2.7k
24k
C4
22nF
C5
100uF
16V
VOUT=-12V/0.45A
C3
220pF
C2
10uF
25V
Ceramic
VIN=12V
C1
10uF
25V
D1
STPS2L25U
Vcc
COMP
GND
OUT
FB
L5972D
1
3
7
5
6
4
8
2
R3
4.7k
C3
22nF
C4
100uF
10V
VOUT=3.3V
C2
220pF
VOUT1=5V
50mA
D2
STPS2L25U
C5
47uF
10V
N1
N2
n=N1/N2=2
9/10
L5972D
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
1.75
0.069
a1
0.1
0.25
0.004
0.010
a2
1.65
0.065
a3
0.65
0.85
0.026
0.033
b
0.35
0.48
0.014
0.019
b1
0.19
0.25
0.007
0.010
C
0.25
0.5
0.010
0.020
c1
45
(typ.)
D (1)
4.8
5.0
0.189
0.197
E
5.8
6.2
0.228
0.244
e
1.27
0.050
e3
3.81
0.150
F (1)
3.8
4.0
0.15
0.157
L
0.4
1.27
0.016
0.050
M
0.6
0.024
S
8
(max.)
(1) D and F do not include mold flash or protrusions. Mold flash or
potrusions shall not exceed 0.15mm (.006inch).
SO8
OUTLINE AND
MECHANICAL DATA
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 parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications 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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L5972D
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