Order this document by LM2574/D
LM2574
Easy Switcher
™
0.5 A
Step-Down Voltage Regulator
The LM2574 series of regulators are monolithic integrated circuits ideally
suited for easy and convenient design of a step–down switching regulator
(buck converter). All circuits of this series are capable of driving a 0.5 A load
with excellent line and load regulation. These devices are available in fixed
output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output version.
These regulators were designed to minimize the number of external
components to simplify the power supply design. Standard series of
inductors optimized for use with the LM2574 are offered by several different
inductor manufacturers.
Since the LM2574 converter is a switch–mode power supply, its efficiency
is significantly higher in comparison with popular three–terminal linear
regulators, especially with higher input voltages. In most cases, the power
dissipated by the LM2574 regulator is so low, that the copper traces on the
printed circuit board are normally the only heatsink needed and no additional
heatsinking is required.
The LM2574 features include a guaranteed
±4%
tolerance on output
voltage within specified input voltages and output load conditions, and
±10%
on the oscillator frequency (±2% over 0°C to +125°C). External shutdown is
included, featuring 60
µA
(typical) standby current. The output switch
includes cycle–by–cycle current limiting, as well as thermal shutdown for full
protection under fault conditions.
Features
EASY SWITCHER™
0.5 A STEP–DOWN
VOLTAGE REGULATOR
SEMICONDUCTOR
TECHNICAL DATA
16
1
DW SUFFIX
PLASTIC PACKAGE
CASE 751G
(SO–16L)
8
1
N SUFFIX
PLASTIC PACKAGE
CASE 626
(DIP–8)
PIN CONNECTIONS
*
*
FB
Sig Gnd
ON/OFF
Pwr Gnd
*
*
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
Adjustable Version Output Voltage Range, 1.23 to 37 V
±4%
max over
Line and Load Conditions
Guaranteed 0.5 A Output Current
Wide Input Voltage Range: 4.75 to 40 V
Requires Only 4 External Components
52 kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby Mode
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit Protection
*
*
Output
*
Vin
*
*
*
(Top View)
FB
Sig Gnd
ON/OFF
Pwr Gnd
1
2
3
4
8
7
6
5
*
Output
*
Vin
(Top View)
* No internal connection, but should be soldered to
*
PC board for best heat transfer.
Applications
Simple and High–Efficiency Step–Down (Buck) Regulators
Efficient Pre–regulator for Linear Regulators
On–Card Switching Regulators
Positive to Negative Converters (Buck–Boost)
Negative Step–Up Converters
Power Supply for Battery Chargers
DEVICE TYPE/NOMINAL OUTPUT VOLTAGE
LM2574–3.3
LM2574–5
LM2574–12
LM2574–15
LM2574–ADJ
3.3 V
5.0 V
12 V
15 V
1.23 V to 37 V
ORDERING INFORMATION
Device
LM2574DW–ADJ
LM2574N–XX
TA = –40° to +125°C
Operating
Temperature Range
Package
SO–16L
DIP–8
XX = Voltage Option, i.e, 3.3, 5, 12, 15 V; and ADJ for
Adjustable Output.
©
Motorola, Inc. 1999
Rev 2, 07/1999
LM2574
Figure 1. Block Diagram and Typical Application
Typical Application
(Fixed Output Voltage Versions)
Feedback
7.0 – 40 V
Unregulated
DC Input
+Vin
Cin
22
µF
5
2
Sig
Gnd
4
Pwr 3
Gnd
LM2574
1
Output
7
ON/OFF
L1
330
µH
D1
1N5819
5.0 V Regulated
Output 0.5 A Load
Cout
220
µF
Representative Block Diagram and Typical Application
+Vin
5
Cin
1
Feedback
R2
Fixed Gain
Error Amplifier Comparator
Current
Limit
Unregulated
DC Input
3.1 V Internal
Regulator
ON/OFF
ON/OFF
3
Output
Voltage Versions
3.3 V
5.0 V
12 V
15 V
For adjustable version
R1 = open, R2 = 0
Ω
R2
(Ω)
1.7 k
3.1 k
8.84 k
11.3 k
R1
1.0 k
Sig Gnd
2
Driver
Freq
Shift
18 kHz
52 kHz
Oscillator
Latch
Output
1.0 Amp
Switch
Reset
Thermal
Shutdown
7
Pwr Gnd
4
D1
L1
Vout
Cout
Load
1.235 V
Band–Gap
Reference
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which
damage to the device may occur).
Rating
Maximum Supply Voltage
ON/OFF Pin Input Voltage
Output Voltage to Ground (Steady State)
DW Suffix, Plastic Package Case 751G
Max Power Dissipation
Thermal Resistance, Junction–to–Air
N Suffix, Plastic Package Case 626
Max Power Dissipation
Thermal Resistance, Junction–to–Ambient
Thermal Resistance, Junction–to–Case
Storage Temperature Range
Minimum ESD Rating
(Human Body Model: C = 100 pF, R = 1.5 kΩ)
Lead Temperature (Soldering, 10 seconds)
Maximum Junction Temperature
NOTE:
ESD data available upon request.
Symbol
Vin
–
–
PD
R
θJA
PD
R
θJA
R
θJC
Tstg
–
–
TJ
Value
45
–0.3 V
≤
V
≤
+Vin
–1.0
Internally Limited
145
Internally Limited
100
5.0
–65°C to +150°C
2.0
260
150
Unit
V
V
V
W
°C/W
W
°C/W
°C/W
°C
kV
°C
°C
2
MOTOROLA ANALOG IC DEVICE DATA
LM2574
OPERATING RATINGS
(Operating Ratings indicate conditions for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed
specifications and test conditions, see the Electrical Characteristics).
Rating
Operating Junction Temperature Range
Supply Voltage
Symbol
TJ
Vin
Value
–40 to +125
40
Unit
°C
V
SYSTEM PARAMETERS
([Note 1] Test Circuit Figure 16)
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version,
Vin = 25 V for the 12 V version, Vin = 30 V for the 15 V version. ILoad = 100 mA. For typical values TJ = 25°C, for min/max values TJ is the
operating junction temperature range that applies [Note 2], unless otherwise noted).
Characteristic
LM2574–3.3
([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 12 V, ILoad = 100 mA, TJ = 25°C)
Output Voltage (4.75 V
≤
Vin
≤
40 V, 0.1 A
≤
ILoad
≤
0.5 A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 0.5 A)
LM2574–5
([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 12 V, ILoad = 100 mA, TJ = 25°C)
Output Voltage (7.0 V
≤
Vin
≤
40 V, 0.1 A
≤
ILoad
≤
0.5 A)
T
J = 25°C
T
J = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 0.5 A)
LM2574–12
([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 25 V, ILoad = 100 mA, TJ = 25°C)
Output Voltage (15 V
≤
Vin
≤
40 V, 0.1 A
≤
ILoad
≤
0.5 A)
T
J = 25°C
T
J = –40 to +125°C
Efficiency (Vin = 15 V, ILoad = 0.5 A)
LM2574–15
([Note 1] Test Circuit Figure 16)
Output Voltage (Vin = 30 V, ILoad = 100 mA, TJ = 25°C)
Output Voltage (18 V < Vin < 40 V, 0.1 A < ILoad < 0.5 A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 18 V, ILoad = 0.5 A)
LM2574 ADJUSTABLE VERSION
([Note 1] Test Circuit Figure 16)
Feedback Voltage Vin = 12 V, ILoad = 100 mA, Vout = 5.0 V, TJ = 25°C
Feedback Voltage 7.0 V
≤
Vin
≤
40 V, 0.1 A
≤
ILoad
≤
0.5 A, Vout = 5.0 V
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 0.5 A, Vout = 5.0 V)
VFB
VFBT
1.193
1.18
η
–
1.23
77
1.267
1.28
–
%
1.217
1.23
1.243
V
V
Vout
Vout
14.4
14.25
η
–
15
88
15.6
15.75
–
%
14.7
15
15.3
V
V
Vout
Vout
11.52
11.4
η
–
12
–
88
12.48
12.6
–
%
11.76
10
12.24
V
V
Vout
Vout
4.8
4.75
η
–
5.0
77
5.2
5.25
–
%
4.9
5.0
5.1
V
V
Vout
Vout
3.168
3.135
η
–
3.3
–
72
3.432
3.465
–
%
3.234
3.3
3.366
V
V
Symbol
Min
Typ
Max
Unit
NOTES:
1. External components such as the catch diode, inductor, input and output capacitors can affect the switching regulator system
performance. When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as
shown in the system parameters section of the Electrical Characteristics.
2. Tested junction temperature range for the LM2574: Tlow = –40°C Thigh = +125°C
MOTOROLA ANALOG IC DEVICE DATA
3
LM2574
SYSTEM PARAMETERS
([Note 1] Test Circuit Figure 16)
ELECTRICAL CHARACTERISTICS
(continued)
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version,
Vin = 25 V for the 12 V version, Vin = 30 V for the 15 V version. ILoad = 100 mA. For typical values TJ = 25°C, for min/max values TJ is the
operating junction temperature range that applies [Note 2], unless otherwise noted).
Characteristic
ALL OUTPUT VOLTAGE VERSIONS
Feedback Bias Current Vout = 5.0 V (Adjustable Version Only)
TJ = 25°C
TJ = –40 to +125°C
Oscillator Frequency (Note 3)
TJ = 25°C
TJ = 0 to +125°C
TJ = –40 to +125°C
Saturation Voltage (Iout = 0.5 A, [Note 4])
TJ = 25°C
TJ = –40 to +125°C
Max Duty Cycle (“on”) [Note 5]
Current Limit Peak Current (Notes 3 and 4)
TJ = 25°C
TJ = –40 to +125°C
Output Leakage Current (Notes 6 and 7), TJ = 25°C
Output = 0 V
Output = – 1.0 V
Quiescent Current (Note 6)
TJ = 25°C
TJ = –40 to +125°C
Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”))
TJ = 25°C
TJ = –40 to +125°C
ON/OFF Pin Logic Input Level
Vout = 0 V
TJ = 25°C
TJ = –40 to +125°C
Nominal Output Voltage
TJ = 25°C
TJ = –40 to +125°C
ON/OFF Pin Input Current
ON/OFF Pin = 5.0 V (“off”), TJ = 25°C
ON/OFF Pin = 0 V (“on”), TJ = 25°C
Ib
–
–
fO
–
47
42
Vsat
–
–
DC
ICL
0.7
0.65
IL
–
–
IQ
–
–
Istby
–
–
VIH
2.2
2.4
VIL
–
–
IIH
IIL
–
–
1.2
–
15
0
1.0
0.8
µA
30
5.0
1.4
–
–
–
60
–
200
400
V
5.0
–
9.0
11
µA
0.6
10
2.0
30
mA
1.0
–
1.6
1.8
mA
93
1.0
–
98
1.2
1.4
–
%
A
52
52
–
–
58
63
V
25
–
100
200
kHz
nA
Symbol
Min
Typ
Max
Unit
NOTES:
1. External components such as the catch diode, inductor, input and output capacitors can affect the switching regulator system
performance. When the LM2574 is used as shown in the Figure 16 test circuit, the system performance will be as
shown in the system parameters section of the Electrical Characteristics.
2. Tested junction temperature range for the LM2574: Tlow = –40°C Thigh = +125°C
3. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated output
voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average power dissipation of
the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to the output pin.
5. Feedback (Pin 4) removed from output and connected to 0 V.
6. Feedback (Pin 4) removed from output and connected to 12 V for the Adjustable, 3.3 V, and 5.0 V versions, and 25 V for the 12 V and 15 V
versions, to force the output transistor OFF.
7. Vin = 40 V.
4
MOTOROLA ANALOG IC DEVICE DATA
LM2574
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 16)
Figure 2. Normalized Output Voltage
1.0
Vout , OUTPUT VOLTAGE CHANGE (%)
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–50
–25
0
25
60
75
100
125
Vin = 20 V
ILoad = 100 mA
Normalized at TJ = 25°C
Vout , OUTPUT VOLTAGE CHANGE (%)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
0
5.0
10
15
20
25
30
35
40
12 V and 15 V
3.3 V, 5.0 V and ADJ
ILoad = 100 mA
TJ = 25°C
Figure 3. Line Regulation
TJ, JUNCTION TEMPERATURE (°C)
Vin, INPUT VOLTAGE (V)
Figure 4. Dropout Voltage
2.0
INPUT – OUTPUT DIFFERENTIAL (V)
L = 300
µH
1.5
ILoad = 500 mA
I O, OUTPUT CURRENT (A)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0
–50
–25
0
25
60
75
100
125
0.7
–50
–25
Figure 5. Current Limit
Vin = 25 V
1.0
ILoad = 100 mA
0.5
0
25
60
75
100
125
TJ, JUNCTION TEMPERATURE (°C)
TJ, JUNCTION TEMPERATURE (°C)
Figure 6. Quiescent Current
Istby , STANDBY QUIESCENT CURRENT (
µ
A)
20
IQ , QUIESCENT CURRENT (mA)
18
16
14
12
10
8.0
6.0
4.0
0
5.0
10
15
20
25
30
35
40
ILoad = 100 mA
ILoad = 500 A
Vout = 5.0 V
Measured at
Ground Pin
TJ = 25°C
200
180
160
140
120
100
80
60
40
20
0
–50
Figure 7. Standby Quiescent Current
VON/OFF = 5.0 V
Vin = 40 V
Vin = 12 V
–25
0
25
60
75
100
125
Vin, INPUT VOLTAGE (V)
TJ, JUNCTION TEMPERATURE (°C)
MOTOROLA ANALOG IC DEVICE DATA
5
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