STMICROELECTRONICS L4976

L4976
1A step down switching regulator
Features
■
Up to 1A step down converter
■
Operating input voltage from 8v to 55v
■
Precise 5.1V reference voltage
■
Output voltage adjustable from 0.5V to 50V
■
Switching frequency adjustable up to 300kHz
■
Voltage feedforward
■
Zero load current operation
■
Internal current limiting (pulse-bypulse
■
and hiccup mode)
■
Protection against feedback disconnection
■
Thermal shutdown
Figure 1.
DIP8
SO16W
Description
The L4976 is a step down monolithic power
switching regulator delivering 1A at a voltage
between 3.3V and 50V (selected by a simple
external divider). Realized in BCD mixed
technology, the device uses an internal power DMOS transistor (with a typical Rds(ON) of 0.25Ω) to
obtain very high efficency and high switching
speed. A switching frequency up to 300KHz is
achievable (the maximum power dissipation of the
packages must be observed). A wide input
voltage range between 8V to 55V and output
voltages regulated from 3.3V to 40V cover the
majority of today’s applications. Features of this
new generations of DC-DC converter include
pulse-by-pulse current limit, hiccup mode for short
circuit protection, voltage feedforward regulation,
protection against feedback loop disconnection
and thermal shutdown. The device is available in
plastic dual in line, MINIDIP 8 for standard
assembly, and SO16W for SMD assembly.
Typical application circuit
Vi=8V to 55V
5
8
R1
20K
L4976
3
C1
220µF
63V
C7
220nF
C2
2.7nF
2
4
1
7
R2
9.1K
C4
22nF
April 2007
Rev 7
L1
260µH
(77120)
6
C6
100nF
D1
GI
SB360
VO=3.3V/1A
C8
330µF
1/17
www.st.com
17
Contents
L4976
Contents
1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
2.1
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3
Operating temperature rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5
Typical charcteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7
Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2/17
L4976
1
Block diagram
Block diagram
Figure 2.
Block diagram
VCC
5
THERMAL
SHUTDOWN
VOLTAGES
MONITOR
CBOOT
CHARGE
VREF
2
VREF
5.1V
COMP
FB
INTERNAL
REFERENCE
7
8
6
3.3V
E/A
PWM
R
Q
S
3.3V
CBOOT
CHARGE
AT LIGHT
LOADS
DRIVE
OSCILLATOR
3
OSC
1
GND
BOOT
4
OUT
3/17
Pin settings
L4976
2
Pin settings
2.1
Pin connection
Figure 3.
Pin connection (top view)
GND
1
8
FB
VREF
2
7
COMP
OSC
3
6
BOOT
OUT
4
5
VCC
N.C.
1
16
N.C.
GND
2
15
N.C.
VREF
3
14
FB
OSC
4
13
COMP
OUT
5
12
BOOT
OUT
6
11
VCC
N.C.
7
10
N.C.
N.C.
8
9
N.C.
SO16
DIP8
2.2
Pin description
Table 1. Pin description
N° Pin
Name
Description
DIP8
SO16W (1)
1
2
GND
Ground
2
3
VREF
5.1V Reference voltage with 20mA current capability.
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
VCC
Unregulated 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 to this pin
results in an output voltage of 3.3V. An external resistive
divider is required for higher output voltages.
1. Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die.
4/17
L4976
Electrical data
3
Electrical data
3.1
Maximum ratings
Table 2. Absolute maximum ratings
Symbol
Parameter
DIP8
S016W
V5
V11
V4
V5, V6
I4
I5, I6
V6-V5
V12-V11
V6
V12
V7
V8
Unit
Input voltage
58
V
Output DC voltage
-1
V
Output peak voltage at t = 0.1µs, f = 200kHz
-5
V
Maximum output current
internal limit
14
V
Bootstrap voltage
70
V
V13
Analogs input voltage (VCC = 24V)
12
V
(VCC = 20V)
6
V
V14
-0.3
V
DIP8
1
W
SO16
0.8
W
-40 to 150
°C
PTOT
TJ,TSTG
3.2
Value
Power dissipation a TA ≤ 60°C
Junction and storage temperature
Thermal data
Table 3. Thermal data
Symbol
Parameter
DIP8
S016W
Unit
RthJA
Maximum thermal resistance junction-ambient
90 (1)
110 (1)
°C/W
1. Package mounted on board
3.3
Operating temperature rating
Table 4. Operating temperature rating
Symbol
TJ
Parameter
Junction temperature range
Value
Unit
-40 to 150
°C
5/17
Electrical characteristics
4
L4976
Electrical characteristics
Table 5. Electrical characteristics
(TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.)
Symbol
Parameter
Test condition
Min
Typ
Max
Unit
55
V
Dynamic characteristic
VI
VO
Vd
Operating input voltage range
Output voltage
Dropout voltage
VO = 3.3 to 50V; IO = 1A (1)
8
IO = 0.5A
3.33
3.36
3.39
V
IO = 0.2 to 1A
3.292
3.36
3.427
V
VCC = 8 to 55V (1)
3.22
3.36
3.5
V
0.29
0.367
V
0.587
V
2.5
A
VCC = 10V; IO = 1A
(1)
Il
fs
SVRR
Maximum limiting current
VCC = 8 to 55V (1)
Efficiency
VO = 3.3V; IO = 1A
Switching frequency
(1)
1.5
2
85
90
100
Supply voltage ripple rejection
VI = VCC + 2VRMS; VO = Vref;
IO = 1.A; fripple = 100Hz
Voltage stability of switching
frequency
VCC = 8 to 55V
3
Temp. stability of switching
frequency
TJ = 0 to 125°C
4
%
110
60
KHz
dB
6
%
%
Reference section
Reference voltage
Iref = 0 to 10mA; (1)
5.0
5.1
5.2
V
4.950
5.1
5.250
V
5
10
VCC = 8 to 55V
Line regulation
Iref = 0mA;
mV
VCC = 8 to 55V
Load regulation
Short circuit current
6/17
Vref = 0 to 5mA;
2
10
mV
VCC = 0 to 20mA
6
25
mV
65
100
mA
30
L4976
Electrical characteristics
Table 5. Electrical characteristics (continued)
(TJ = 25°C, COSC = 2.7nF, ROSC = 20kΩ, VCC = 24V, unless otherwise specified.)
Symbol
Parameter
Test condition
Min
Typ
Max
Unit
4
6
mA
2.5
3.5
mA
3.36
3.39
V
5
10
mV
DC Characteristics
Iqop
Iq
Total operating quiescent current
Quiescent current
Duty Cycle = 0; VFB = 3.8V
Error Amplifier
VFB
Voltage feedback input
RL
Line regulation
Ref. voltage stability vs
temperature
3.33
VCC = 8 to 55V
(1)
mV/°
C
0.4
VoH
High level output voltage
VFB = 2.5V
VoL
Low level output voltage
VFB = 3.8V
Source output current
Vcomp = 6V; VFB = 2.5V
180
220
µA
IO sink
Sink output current
Vcomp = 6V; VFB = 3.8V
200
300
µA
Ib
Source bias current
IO source
SVRR E/A
gm
10.3
V
0.65
2
3
V
µA
Supply voltage ripple rejection
Vcomp = Vfb; VCC = 8 to 55V
60
80
dB
DC open loop gain
RL = ∞
50
57
dB
Transconductance
Icomp = -0.1 to 0.1mA
Vcomp = 6V
2.5
ms
Oscillator section
Ramp valley
Ramp peak
0.78
0.85
0.92
V
VCC = 8V
2
2.15
2.3
V
VCC = 55V
9
9.6
10.2
V
95
97
Maximum duty cycle
Maximum frequency
Duty cycle = 0%
Rosc = 13kW, Cosc = 820pF
%
300
kHz
1. Specification refered to Tj from 0 to 125°C
7/17
Typical charcteristics
5
L4976
Typical charcteristics
Figure 4.
Quiescent drain current vs.
input voltage
Iq
(mA)
D97IN724
200KHz
R1=22K
C2=1.2nF
5
Line regulation
VO
(V)
3.378
D97IN734
VCC=35V
3.376
3.374
100KHz
R1=20K
C2=2.7nF
4
Figure 5.
Tj=25˚C
3.372
3.370
3
Tj=125˚C
3.368
0Hz
3.366
3.364
2
Tamb=25˚C
0% DC
3.362
3.360
1
0
Figure 6.
0
Vcc(V)
5 10 15 20 25 30 35 40 45 50
Quiescent current vs. junction Figure 7.
temperature
D97IN731
Iq
(mA)
4
Switching frquency vs. R1 and
C2
fsw
(KHz)
D97IN784
500
200KHz
R1=22K
C2=1.2nF
5
0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Tamb=25˚C
0.8
2nF
200
1.2
100KHz
R1=20K
C2=2.7nF
nF
100
2.2
nF
50
3
3.3n
F
0Hz
2
4.7n
F
20
VCC=35V
0% DC
5.6n
F
10
5
1
-50 -30 -10 10 30 50 70 90 110
8/17
Tj(˚C)
0
20
40
60
80
R1(KΩ)
L4976
Typical charcteristics
Figure 8.
Load regulation
Figure 9.
VO
(V)
D97IN733
3.377
Switching frequency vs. input
voltage
fsw
(KHz)
D97IN735
107.5
Tj=125˚C
105.0
3.376
102.5
3.375
Tj=25˚C
Tj=25˚C
3.374
100.0
3.373
97.5
3.372
95.0
3.371
92.5
90.0
3.370
0
0
5 10 15 20 25 30 35 40 45 50 VCC(V)
Figure 10. Switching frequency vs.
junction temperature
fsw
(KHz)
5 10 15 20 25 30 35 40 45 50 VCC(V)
Figure 11. Efficiency vs. output current
D97IN785
∆V
(V)
D97IN736
Tj=125˚C
0.5
105
0.4
C
5˚
=2
Tj
0.3
100
Tj=-25˚C
0.2
95
0.1
0.0
90
-50
0
50
100
Tj(˚C)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Figure 12. Dropout voltage between pin 5 Figure 13. Efficiency vs. output current
and 4
∆V
(V)
0.5
D97IN736
Tj=125˚C
η
(%)
D97IN739
VCC=8V
90
85
0.4
=2
Tj
VCC=12V
C
5˚
VCC=24V
80
0.3
VCC=48V
75
0.2
Tj=-25˚C
70
0.1
fsw=100KHz
VO=3.36V
65
60
0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
9/17
Typical charcteristics
L4976
Figure 14. Efficiency vs output voltage
η
(%)
D97IN737
100KHz
96
94
Figure 15. Efficiency vs. output current
D97IN740
η
(%)
VCC=8V
90
200KHz
VCC=12V
VCC=24V
85
92
80
VCC=48V
90
75
VCC=35V
IO=1.5A
88
86
70
84
65
82
0
5
10
15
20
25
VO(V)
Figure 16. Efficiency vs. output current
η
(%)
D97IN741
fsw=200KHz
VO=5.1V
60
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Figure 17. Efficiency vs. Vo
Pdiss
(mW)
D97IN744
VCC=35V
fsw=100KHz
VCC=8V
90
800
85
VCC=12V
80
IO=1.5A
600
VCC=24V
75
IO=1A
400
70
VCC=48V
IO=0.5A
65
fsw=200KHz
VO=3.36V
200
60
55
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Figure 18. Efficiency vs. VCC
0
0
5
10
D97IN742
Ilim
(A)
V0
85
25
30 V0(V)
D97IN747
V0 =5
SW =1
20
Figure 19. Pulse by pulse limiting
current vs. junction
temperature.
η
(%)
.1V-f
15
fsw=100KHz
VCC=35V
2.9
00KH
z
=5
.1V
2.8
-fS
W=
20
V0 =
0K
Hz
2.7
3.36
80
V-f
SW =
V
0 =3
.36
100
V-
fS
KHz
W=
20
2.5
0K
75
2.6
Hz
IO=1.5A
2.4
70
10/17
2.3
0
10
20
30
40
50 VCC(V)
-50 -25
0
25
50
75 100 125 Tj(˚C)
L4976
Typical charcteristics
Figure 20. Power dissipation vs. VCC
Pdiss
(mW)
Figure 21. Load transient
D97IN743
VO=5.1V
fsw=100KHz
800
IO=1.5A
600
IO=1A
400
IO=0.5A
200
0
0
10
20
30
40
50 VCC(V)
Figure 22. Line transient
VCC
(V)
Figure 23. Open loop frequency and
phase of error amplifier
GAIN
(dB)
D97IN786
D97IN787
Phase
30
50
GAIN
20
0
0
VO
(mV)
-50
45
100
-100
10
1
IO = 1A
fsw = 100KHz
2
90
Phase
0
135
-150
-100
1ms/DIV
-200
10
102 103 104 105 106 107 108 f(Hz)
11/17
Package mechanical data
6
L4976
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect . The category of
second level interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com
12/17
L4976
Package mechanical data
Figure 24. DIP8 mechanical data & package dimensions
mm
inch
DIM.
MIN.
A
TYP.
MAX.
MIN.
3.32
TYP.
MAX.
0.131
a1
0.51
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
0.020
D
E
10.92
7.95
9.75
0.430
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
Z
3.18
OUTLINE AND
MECHANICAL DATA
3.81
1.52
0.125
0.150
DIP-8
0.060
13/17
Package mechanical data
L4976
Figure 25. SO16Wide mechanical data & package dimensions
mm
inch
DIM.
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
2.35
2.65
0.093
0.104
A1
0.10
0.30
0.004
0.012
B
0.33
0.51
0.013
0.200
C
0.23
0.32
0.009
0.013
D (1)
10.10
10.50
0.398
0.413
E
7.40
7.60
0.291
0.299
e
1.27
0.050
H
10.0
10.65
0.394
0.419
h
0.25
0.75
0.010
0.030
L
0.40
1.27
0.016
0.050
k
ddd
OUTLINE AND
MECHANICAL DATA
0˚ (min.), 8˚ (max.)
0.10
0.004
(1) “D” dimension does not include mold flash, protusions or gate
burrs. Mold flash, protusions or gate burrs shall not exceed
0.15mm per side.
SO16 (Wide)
0016021 C
14/17
L4976
7
Order code
Order code
Table 6. Order code
Part number
Package
Packaging
L4976
DIP8
Tube
L4976D
SO16W
Tube
L4976D013TR
SO16W
Tape and reel
15/17
Revision history
8
L4976
Revision history
Table 7. Revision history
16/17
Date
Revision
Changes
5-Aug-2001
6
First Issue
3-Apr-2007
7
Document reformatted, updated dropout voltage values in Table 5 on
page 6
L4976
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17/17