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Электронный компонент: L5971D

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UP TO 1.5A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 6.5V
TO 28V
PRECISE 1.26V (
1%) INTERNAL REFER-
ENCE VOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM
1.26V TO 20V
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 L5971 is a step down monolithic power
switching regulator delivering 1.5A at a voltage
between 1.26V and 20V (selected by a simple
external divider). Realized in BCD mixed technol-
ogy, the device uses an internal power D-MOS
transistor (with a typical Rdson of 0.25
) to ob-
tain very high efficency and high switching speed.
A switching frequency up to 500KHz is achiev-
able (the maximum power dissipation of the pack-
ages must be observed).
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 SO16 for
SMD assembly.
Typical Applications:
- High efficiency step-down converter
- Portable computers
- Battery charger
- Distributed power
- PDAs and Mobile Comminicators
May 2000
ORDERING NUMBERS: L5971 (Minidip)
L5971D (SO16)
L5971
1.5A STEP DOWN SWITCHING REGULATOR
Minidip
SO16W
D98IN832C
5(11)
2(3)
8(14)
4(5,6)
1(2)
L5971
C
1
47
F
30V
C
8
330
F
V
O
=2.5V/1.5A
Vi=6V to 28V
R
1
22K
C
2
1.2nF
R
2
9.1K
C
4
22nF
3(4)
7(13)
L1
30
H
6(12)
D1
STPS
3L40U
C
5
47nF
C
6
100nF
R
3
R
4
TYPICAL APPLICATION CIRCUIT
1/11
PIN FUNCTIONS
DIP
SO (*)
Name
Function
1
2
GND
Ground
2
3
SS_INH
A logic signal (active low) disables the device (sleep mode operation).
A capacitor connected between this pin and ground determines the soft start time.
When this pin is grounded disables the device (driven by open collector/drain).
3
4
OSC
An external resistor connected between the unregulated input voltage and this pin and
a capacitor connected from this pin to ground fix the switching frequency. (Line feed
forward is automatically obtained)
4
5, 6
OUT
Stepdown regulator output
5
11
V
CC
Not regulated DC input voltage
6
12
BOOT
A capacitor connected between this pin and OUT allows to drive the internal VDMOS
7
13
COMP
E/A output to be used for frequency compensation
8
14
FB
Stepdown feedback input. Connecting directly this pin to the output 1.26V is obtained; a
voltage divider is requested for higher output voltages
(*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die.
PIN CONNECTIONS
GND
SS_INH
OSC
OUT
1
3
2
4
VCC
BOOT
COMP
FB
8
7
6
5
D97IN595
N.C.
GND
SS_INH
OSC
OUT
N.C.
OUT
N.C.
N.C.
N.C.
BOOT
VCC
COMP
FB
N.C.
N.C.
1
3
2
4
5
6
7
8
14
13
12
11
10
9
15
16
D97IN596
INHIBIT
SOFTSTART
VOLTAGES
MONITOR
THERMAL
SHUTDOWN
E/A
PWM
1.26V
OSCILLATOR
R
S
Q
INTERNAL
REFERENCE
INTERNAL
SUPPLY
1.26V
5.1V
DRIVE
CBOOT
CHARGE
CBOOT
CHARGE
AT LIGHT
LOADS
2
7
8
FB
COMP
SS_INH
3
1
4
6
5
BOOT
OSC
GND
OUT
VCC
D98IN833
BLOCK DIAGRAM
Minidip
SO16W
L5971
2/11
ELECTRICAL CHARACTERISTICS (Tj = 25
C, Cosc = 2.7nF, Rosc = 20k
, V
CC
= 12V, unless other-
wise specified.) * Specification Refered to Tj from 0 to 125
C
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
DYNAMIC CHARACTERISTIC
V
I
Operating input voltage range
*
6.5
28
V
V
o
Output voltage
I
o
= 0.5A
1.247
1.26
1.273
V
I
o
= 0.2 to 1.5A
1.235
1.26
1.285
V
V
cc
= 6.5 to 25V
*
1.21
1.26
1.31
V
V
d
Dropout voltage
V
cc
= 10V; I
o
= 1.5A
0.44
0.55
V
*
0.88
V
I
l
Maximum limiting current
V
cc
= 6.5 to 25V
*
2
2.5
3
A
Efficiency
V
o
= 3.3V; I
o
= 1.5A
85
%
f
s
Switching frequency
*
90
100
110
KHz
SVRR
Supply voltage ripple rejection
V
i
= V
cc
+2V
RMS
; V
o
= V
ref
;
I
o
= 1.5A; f
ripple
= 100Hz
60
dB
Voltage stability of switching
frequency
Vcc = 6.5 to 25V
3
6
%
Temp. stability of switching
frequency
T
j
= 0 to 125
C
4
%
Soft Start
Soft start charge current
30
40
50
A
Soft start discharge current
6
10
14
A
Inhibit
V
LL
Low level voltage
*
0.9
V
I
sLL
Isource Low level
*
5
15
A
THERMAL DATA
Symbol
Parameter
Minidip
SO16
Unit
R
th(j-amb)
Thermal Resistance Junction to ambient
Max.
90 (*)
110 (*)
C/W
(*) Package mounted on board.
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
Minidip
S016
V
5
, V
3
V
11
, V
4
Input voltage
30
V
V
4
V
5
,V
6
Output DC voltage
Output peak voltage at t = 0.1
s f=200KHz
-1
-5
V
V
I
4
I
5
,I
6
Maximum output current
int. limit.
V
6
-V
5
V12-V
11
14
V
V
6
V
12
Bootstrap voltage
45
V
V
7
,V
2
V
13
,V
3
Analogs input voltage (V
CC
= 12V)
10
V
V
8
V
14
(V
CC
= 20V)
6
-0.3
V
V
P
tot
Power dissipation a T
amb
60
C
Minidip
1
W
SO16
0.8
W
T
j
,T
stg
Junction and storage temperature
-40 to 150
C
L5971
3/11
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
DC Characteristics
I
qop
Total operating quiescent
current
Pin 5 (Pin 11)
3
4.5
mA
I
q
Quiescent current
Duty Cycle = 0; V
FB
= 1.7V
2.8
3.5
mA
I
qst-by
Total stand-by quiescent
current
V
inh
<0.9V
100
200
A
Vcc = 25V; V
inh
<0.9V
150
300
A
Error Amplifier
V
FB
Voltage Feedback Input
1.247
1.26
1.273
V
R
L
Line regulation
Vcc = 6.5 to 25V
5
10
mV
Ref. voltage stability vs
temperature
*
0.4
mV/
C
V
oH
High level output voltage
V
FB
= 0.8V
8.7
V
V
oL
Low level output voltage
V
FB
= 1.7V
0.65
V
I
o source
Source output current
V
comp
= 3V; V
FB
= 0.8V
180
250
A
I
o sink
Sink output current
V
comp
= 3V; V
FB
= 1.7V
200
300
A
I
b
Source bias current
2
3
A
SVRR E/A
Supply voltage ripple rejection
V
comp
= V
fb
; Vcc = 6.5 to 25V
60
80
dB
DC open loop gain
R
L
=
50
57
dB
gm
Transconductance
I
comp
= -0.1 to 0.1mA
V
comp
= 6V
4.3
mS
Oscillator Section
Ramp Valley
0.74
0.81
0.88
V
Ramp peak
Vcc = 6.5V
1.80
1.87
1.94
V
Vcc = 25V
4.72
4.79
4.86
V
Maximum duty cycle
95
97
%
Maximum Frequency
Duty Cycle = 0%
R
osc
= 13k
, C
osc
= 820pF
500
kHz
ELECTRICAL CHARACTERISTICS (continued)
L5971
4/11
D98IN832C
5(11)
2(3)
8(14)
4(5,6)
1(2)
L5971
C
1
47
F
30V
C
8
330
F
V
O
=2.5V/1.5A
Vi=6V to 28V
R
1
22K
C
2
1.2nF
R
2
9.1K
C
4
22nF
3(4)
7(13)
L1
30
H
6(12)
D1
STPS
3L40U
C
5
47nF
C
6
100nF
R
3
R
4
Figure 1. Test and valutation board circuit.
V
O
(V)
R3 (K
) R4 (K
)
1.8
1
2
1.5
0.5
2
2.5
2
2
3.3
8.2
4.7
5.1
12
3.6
12
27
3
15
23
2
Figure 2. PCB and component layout of the figure 1.
SOLDER SIDE
COMPONENT SIDE
L5971
5/11
0
5
10
15
20
25
Vcc(V)
1
2
3
4
5
Iq
(mA)
200KHz
R
1
=22K
C
2
=1.2nF
0Hz
D98IN942
Tamb=25
C
0% DC
100KHz;
R
1
=20K
C
2
=2.7nF
Figure 3. Quiescent drain current vs. input
voltage.
0
5
10
15
20
25 V
CC
(V)
60
70
80
90
100
110
120
130
140
150
Ibias
(
A)
D98IN944
Tj=25
C
Tj=125
C
Vss=GND
Figure 5. Stand-by drain current vs. input
voltage
-50 -30 -10 10 30 50 70 90 110
Tj(
C)
1
2
3
4
5
Iq
(mA)
D98IN943
0Hz
200KHz; R
1
=22K; C
2
=1.2nF
V
CC
=20V
0% DC
100KHz; R
1
=20K; C
2
=2.7nF
Figure 4. Quiescent current vs. junction
temperature
0
20
40
60
80
R1(K
)
5
10
20
50
100
200
500
fsw
(KHz)
D97IN784
0.82nF
1.2nF
2.2nF
3.3nF
4.7nF
5.6nF
Tamb=25
C
Figure 7. Switching frquency vs. R1 and C2
0
5
10
15
20
25 V
CC
(V)
3.370
3.371
3.372
3.373
3.374
3.375
3.376
3.377
V
O
(V)
D98IN945
Tj=25
C
Tj=125
C
Figure 6. Line Regulation
0
5
10
15
20
25 V
CC
(V)
90.0
92.5
95.0
97.5
100.0
102.5
105.0
107.5
fsw
(KHz)
D98IN947
Tj=25
C
Figure 8. Switching Frequency vs. input
voltage.
L5971
6/11
0
5
10
15
20
25
V
O
(V)
82
84
86
88
90
92
94
96
(%)
D98IN948
100KHz
V
CC
=20V
I
O
=1.5A
200KHz
Figure 11. Efficiency vs output voltage.
0.0
0.2 0.4
0.6 0.8 1.0
1.2 1.4 I
O
(A)
0.0
0.1
0.2
0.3
0.4
0.5
V
(V)
Tj=25
C
Tj=125
C
D97IN736
Tj=-25
C
Figure 10. Dropout voltage between pin 5
and 4.
-50
0
50
100
Tj(
C)
90
95
100
105
fsw
(KHz)
D97IN785
Figure 9. Switching frequency vs. junction
temperature.
0.0
0.2
0.4 0.6
0.8
1.0
1.2
1.4 I
O
(A)
75
80
85
90
(%)
D98IN950
V
CC
=8V
fsw=200KHz
V
O
=3.36V
V
CC
=12V
V
CC
=18V
Figure 13. Efficiency vs output current.
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 I
O
(A)
75
80
85
90
(%)
D98IN949
V
CC
=8V
fsw=200KHz
V
O
=5.1V
V
CC
=12V
V
CC
=18V
Figure 12. Efficiency vs. output current.
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 Io(A)
60
65
70
75
80
85
90
(%)
Vcc=8V
Vcc=12V
Vcc=18V
Fsw=200KHz
Vo=2.5V
D98IN941
Figure 14. Efficiency vs. output current.
L5971
7/11
20
22
24
26
28V
CCmax
(V)
0
40
80
120
160
L
(
H)
D98IN952
fsw=100KHz
680nF
470nF
330nF
220nF
100nF
Figure 16. Soft start capacitor selection vs. In-
ductor and V
ccmax
Figure 15. Load transient.
10
10
3
10
5
10
7
f(Hz)
10
2
10
4
10
6
10
8
-200
-150
-100
-50
GAIN
(dB)
0
50
Phase
0
45
90
135
D97IN787
GAIN
Phase
Figure 18. Open loop frequency and phase of
error amplifier.
20
22
24
26
28 V
CCmax
(V)
0
50
100
150
L
(
H)
56nF
fsw=200KHz
D98IN953
47nF
33nF
22nF
Figure 17. Soft start capacitor selection vs. In-
ductor and V
ccmax
L5971
8/11
Minidip
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
3.32
0.131
a1
0.51
0.020
B
1.15
1.65
0.045
0.065
b
0.356
0.55
0.014
0.022
b1
0.204
0.304
0.008
0.012
D
10.92
0.430
E
7.95
9.75
0.313
0.384
e
2.54
0.100
e3
7.62
0.300
e4
7.62
0.300
F
6.6
0.260
I
5.08
0.200
L
3.18
3.81
0.125
0.150
Z
1.52
0.060
OUTLINE AND
MECHANICAL DATA
L5971
9/11
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
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.)
h x 45
A
e
B
D
E
A1
H
L
C
K
16
1
8
9
SO16 Wide
OUTLINE AND
MECHANICAL DATA
L5971
10/11
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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. 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.
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L5971
11/11