LM2575
Micrel
LM2575
52kHz Simple 1A Buck Regulator
General Description
The LM2575 series of monolithic integrated circuits provide
all the active functions for a step-down (buck) switching
regulator. Fixed versions are available with a 3.3V, 5V, 12V,
fixed output. Adjustable versions have an output voltage
range from 1.23V to 37V. Both versions are capable of driving
a 1A load with excellent line and load regulation.
These regulators are simple to use because they require a
minimum number of external components and include internal
frequency compensation and a fixed-frequency oscillator.
The LM2575 series offers a high efficiency replacement for
popular three-terminal adjustable linear regulators. It
substantially reduces the size of the heat sink, and in many
cases no heat sink is required.
A standard series of inductors available from several different
manufacturers are ideal for use with the LM2575 series. This
feature greatly simplifies the design of switch-mode power
supplies.
The feedback voltage is guaranteed to
±2%
tolerance for
adjustable versions, and the output voltage is guaranteed to
±3%
for fixed versions, within specified input voltages and
output load conditions. The oscillator frequency is guaranteed
to
±10%.
External shutdown is included, featuring less than
200µA standby current. The output switch includes cycle-by-
cycle current limiting and thermal shutdown for full protection
under fault conditions.
Features
• 3.3V, 5V, 12V, and adjustable output versions
• Voltage over specified line and load conditions:
Fixed version:
±3%
max. output voltage
Adjustable version:
±2%
max. feedback voltage
• Guaranteed 1A output current
• Wide input voltage range:
4V to 40V
• Wide output voltage range
1.23V to 37V
• Requires only 4 external components
• 52kHz fixed frequency internal oscillator
• Low power standby mode I
Q
typically < 200µA
• 80% efficiency (adjustable version typically > 80%)
• Uses readily available standard inductors
• Thermal shutdown and current limit protection
• 100% electrical thermal limit burn-in
Applications
•
•
•
•
•
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (inverting Buck-Boost)
Isolated Flyback Converter using minimum number of
external components
• Negative Boost Converter
Typical Applications
870 20
7V–40V
Unregulated
DC Input
1
4
Feedback
+V
IN
C
IN
100µF
+
LM2575-5.0 Output L1
2
330µH
D1
1N5822
+
+5V, 1A
Regulated
Output
7V–40V
Unregulated
DC Input
1
4
LM2575
Feedback
+V
IN
C
IN
100µF
+
Output L1
2
330µH
D1
1N5822
+
C
OUT
330µF
+5V, 1A
Regulated
Output
R2 3.09k
R1 1k
3
5
Gnd On/Off
C
OUT
330µF
3
5
Gnd On/Off
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package
V
OUT
= 1.23 1 + R2
R1
(
)
Fixed Regulator in Typical Application
Adjustable Regulator in Fixed Output Application
August 1999
1
M2575
LM2575
Micrel
Ordering Information
Part Number
‡
LM2575BN*
LM2575-3.3BN
LM2575-5.0BN
LM2575-12BN
LM2575BWM*
LM2575-3.3BWM
LM2575-5.0BWM
LM2575-12BWM
LM2575BT*
†
LM2575-3.3BT
†
LM2575-5.0BT
†
LM2575-12BT
†
LM2575BU*
LM2575-3.3BU
LM2575-5.0BU
LM2575-12BU
Temperature Range
–40°C to +85
°C
–40°C to +85
°C
–40°C to +85
°C
–40°C to +85
°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
16-pin Plastic DIP
16-pin Plastic DIP
16-pin Plastic DIP
16-pin Plastic DIP
24-pin Wide SOIC
24-pin Wide SOIC
24-pin Wide SOIC
24-pin Wide SOIC
5-lead TO-220
5-lead TO-220
5-lead TO-220
5-lead TO-220
5-lead TO-263
5-lead TO-263
5-lead TO-263
5-lead TO-263
* Adjustable output regulators.
†
Contact factory for bent or staggered leads option.
Pin Configurations
5-LEAD TO-220 (T)
GND
5- ON/OFF
4- FEEDBACK
3- GROUND
2- OUTPUT
1- VIN
GND
5-LEAD TO-263 (U)
5- ON/OFF
4- FEEDBACK
3- GROUND
2- OUTPUT
1- VIN
24-LEAD SOIC (WM)
16-LEAD DIP (N)
NC
NC
OUTPUT
NC
GND
NC
FB
NC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VIN
NC
GND
GND
GND
GND
NC
ON/OFF
PWR GND
NC
NC
NC
NC
NC
FB
SIG GND
NC
ON/OFF
NC
PWR GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
NC
NC
NC
NC
NC
NC
OUTPUT
OUTPUT
NC
VIN
VIN
NC
LM2575
2
August 1999
LM2575
Micrel
Absolute Maximum Ratings
(Note 1)
Maximum Supply Voltage
ON/OFF Pin Input Voltage
Output Voltage to Ground (Steady State)
Power Dissipation
Storage Temperature Range
Minimum ESD Rating
C = 100pF, R = 1.5kΩ
FB Pin
Lead Temperature (soldering, 10 sec.)
Maximum Junction Temperature
45V
–0.3V
≤
V
≤
+40V
–1V
Internally Limited
–65°C to +150°C
2 kV
1 kV
260°C
150°C
Operating Ratings
Temperature Range
Supply Voltage
–40°C
≤
T
J
≤
+125°C
40V
Specifications with standard typeface are for T
J
= 25°C, and those with
boldface type
apply
over
full Operating Temperature Range.
Unless otherwise specified, V
IN
= 12V, and I
LOAD
= 200mA.
LM2575
Symbol
Parameter
Conditions
Typ
Limit
(Note 2)
Units
(Limits)
Electrical Characteristics
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS
(Note 3) Test Circuit
Figure 1
V
OUT
Feedback Voltage
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 5V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
V
IN
= 12V, I
LOAD
= 1A, V
OUT
= 5V
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 3.3V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 3.3V
V
IN
= 12V, I
LOAD
= 1A
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 5V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
V
IN
= 12V, I
LOAD
= 1A
V
IN
= 25V , I
LOAD
= 0.2A
V
OUT
= 12V
0.2A
≤
I
LOAD
≤
1A, 15V
≤
V
IN
≤
40V
V
OUT
= 12V
V
IN
= 25V, I
LOAD
= 1A
1.230
1.217
1.243
1.230
1.193/1.180
1.267/1.280
82
V
V(min)
V(max)
V
V(min)
V(max)
%
V
OUT
Feedback Voltage
LM2575
Efficiency
η
SYSTEM PARAMETERS, 3.3V REGULATORS
(Note 3) Test Circuit
Figure 1
V
OUT
Output Voltage
3.3
3.234
3.366
3.3
3.168/3.135
3.432/3.465
75
V
V(min)
V(max)
V
V(min)
V(max)
%
V
OUT
Output Voltage
LM2575-3.3
Efficiency
η
SYSTEM PARAMETERS, 5V REGULATORS
(Note 3) Test Circuit
Figure 1
V
OUT
Output Voltage
5.0
4.900
5.100
5.0
4.800/4.750
5.200/5.250
82
V
V(min)
V(max)
V
V(min)
V(max)
%
V
OUT
Output Voltage
LM2575-5.0
Efficiency
η
SYSTEM PARAMETERS, 12V REGULATORS
(Note 3) Test Circuit
Figure 1
V
OUT
Output Voltage
12
11.760
12.240
12
11.520/11.400
12.480/12.600
88
V
V(min)
V(max)
V
V(min)
V(max)
%
V
OUT
Output Voltage
LM2575-12
Efficiency
η
August 1999
3
M2575
LM2575
Micrel
Electrical Characteristics (continued)
LM2575
Symbol
Parameter
Conditions
Typ
Limit
(Note 2)
Units
(Limits)
DEVICE PARAMETERS, ADJUSTABLE REGULATOR
I
B
f
O
Feedback Bias Current
V
OUT
= 5V
50
100/500
nA
DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS
Oscillator Frequency
52
47/42
58/63
Saturation Voltage
Max Duty Cycle (ON)
Current Limit
I
OUT
= 1A (Note 4)
(Note 5)
Peak Current, t
ON
≤
3µs (Note 4)
0.9
1.2/1.4
98
93
I
CL
2.2
1.7/1.3
3.0/3.2
2
7.5
30
5
10
Standby Quiescent
Current
Thermal Resistance
ON/OFF Pin = 5V (OFF)
T Package, Junction to Ambient (Note 7)
T Package, Junction to Ambient (Note 8)
T Package, Junction to Case
N Package, Junction to Ambient (Note 9)
WM Package, Junction to Amb. (Note 9)
50
200
65
45
2
85
100
kHz
kHz (min)
kHz (max)
V
V(max)
%
%(min)
A
A(min)
A(max)
mA(max)
mA
mA(max)
mA
mA(max)
µA
µA(max)
°C/W
V
SAT
DC
I
L
Output Leakage Current
V
IN
= 40V, (Note 6),
(Note 6)
Output = 0V
Output = –1V
Output = –1V
I
Q
I
STBY
θ
JA
θ
JA
θ
JC
θ
JA
θ
JA
Quiescent Current
(Note 6)
LM2575
4
August 1999
LM2575
LM2575
Symbol
Parameter
Conditions
Typ
Limit
(Note 2)
Micrel
Units
(Limits)
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS
Test Circuit
Figure 1
V
IH
V
IL
I
IH
I
IL
Note 1:
ON/OFF Pin Logic
Input Level
ON /OFF Pin Logic
Current
V
OUT
= 0V
V
OUT
= 5V
ON /OFF Pin = 5V (OFF)
ON/OFF Pin = 0V (ON)
1.4
1.2
4
2.2/2.4
1.0/0.8
30
V(min)
V(max)
µA
µA(max)
µA
µA(max)
0.01
10
Absolute Maximum Rating indicate limits beyond which damage to the device may occur. 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.
All limits guaranteed at room temperature (standard type face) and at
temperature extremes (bold type face) .
All room temperature limits are
100% production tested. All limits at
temperature extreme
are guaranteed via testing.
External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the
LM2575/LM1575 is used as shown in
Figure 1
test circuit, system performance will be shown in system parameters section of Electrical
Characteristics.
Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output.
Feedback (pin 4) removed from output and connected to 0V.
Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.
Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2" leads in a socket, or
on PC board with minimum copper area.
Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4" leads soldered to PC
board containing approximately 4 square inches of copper area surrounding the leads.
Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower
thermal resistance further.
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Typical Performance Characteristics
Normalized
Feedback Voltage*
NORMALIZED FEEDBACK VOLTAGE (mV)
Feedback Voltage
vs Duty Cycle*
20
FEEDBACK VOLTAGE CHANGE (mV)
25
20
15
10
5
0
-5
-10
-15
-20
-25
-75 -50 -25 0
VIN = 12V
ILOAD = 200mA
Normalized to TJ = 25˚C
15
10
5
0
-5
-10
-15
-20
0
20
40
ILOAD = 200 mA
VIN = 40V
VIN = 7V
25 50 75 100 125 150
60
80
100
JUNCTION TEMPERATURE (˚C)
DUTY CYCLE (%)
* Adjustable version only
August 1999
5
M2575
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