D ts e t
aa h e
R c e t r lc r nc
o h se Ee to is
Ma u a t r dCo o e t
n fc u e
mp n n s
R c e tr b a d d c mp n ns ae
o h se rn e
o oet r
ma ua trd u ig ete dewaes
n fcue sn i r i/ fr
h
p rh s d f m te oiia s p l r
uc a e r
o h r n l u pi s
g
e
o R c e tr waes rce td f m
r o h se
fr e rae r
o
te oiia I. Al rce t n ae
h
r nl P
g
l e rai s r
o
d n wi tea p o a o teOC
o e t h p rv l f h
h
M.
P r aetse u igoiia fcoy
at r e td sn r n la tr
s
g
ts p o rmso R c e tr e eo e
e t rga
r o h se d v lp d
ts s lt n t g aa te p o u t
e t oui s o u rne
o
rd c
me t o e c e teOC d t s e t
es r x e d h
M aa h e.
Qu l yOv riw
ai
t
e ve
• IO- 0 1
S 90
•A 92 cr ct n
S 1 0 et ai
i
o
• Qu l e Ma ua trr Ls (
ai d
n fcues it QML MI- R -
) LP F
385
53
•C a sQ Mitr
ls
lay
i
•C a sVS a eL v l
ls
p c ee
• Qu l e S p l r Ls o D sr uos( L )
ai d u pi s it f it b tr QS D
e
i
•R c e trsacic l u pir oD A a d
o h se i
r ia s p l t L n
t
e
me t aln u t a dD A sa d r s
es lid sr n L tn ad .
y
R c e tr lcrnc , L i c mmi e t
o h se Ee t is L C s o
o
tdo
t
s p ligp o u t ta s t f c so r x e t-
u pyn rd cs h t ai y u tme e p ca
s
t n fr u lya daee u loto eoiial
i s o q ai n r q a t h s r n l
o
t
g
y
s p l db id sr ma ua trr.
u pi
e yn ut
y n fcues
T eoiia ma ua trr d ts e t c o a yn ti d c me t e e t tep r r n e
h r n l n fcue’ aa h e a c mp n ig hs o u n r cs h ef ma c
g
s
o
a ds e ic t n o teR c e tr n fcue v rino ti d vc . o h se Ee t n
n p c ai s f h o h se ma ua trd eso f hs e ie R c e tr lcr -
o
o
isg aa te tep r r n eo i s mio d co p o u t t teoiia OE s e ic -
c u rne s h ef ma c ft e c n u tr rd cs o h r n l M p c a
o
s
g
t n .T pc lv le aefr eee c p r o e o l. eti mii m o ma i m rt g
i s ‘y ia’ au s r o rfrn e up s s ny C r n nmu
o
a
r xmu ai s
n
ma b b s do p o u t h rceiain d sg , i lt n o s mpetsig
y e a e n rd c c aa tr t , e in smuai , r a l e t .
z o
o
n
© 2 1 R cetr l t n s LC Al i t R sre 0 1 2 1
0 3 ohs E cr i , L . lRg s eevd 7 1 0 3
e e oc
h
T l r m r, l s v iw wrcl . m
o e n oe p ae it w . e c o
a
e
s
o ec
LM2576
Micrel, Inc.
LM2576
52kHz Simple 3A Buck Regulator
General Description
The LM2576 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, or 12V
fixed output. Adjustable versions have an output voltage
range from 1.23V to 37V. Both versions are capable of driving
a 3A 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 LM2576 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 LM2576 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 3A 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
7V–40V
Unregulated
DC Input
+V
IN
+
C
IN
100µF
LM2575-5.0 Output L1
2
330µH
3
5
Gnd On/Off
D1
1N5822
1
4
Feedback
+5V, 1A
Regulated
Output
+
C
OUT
330µF
7V–40V
Unregulated
DC Input
1
4
LM2575
Feedback
+V
IN
+
C
IN
100µF
3
5
Gnd On/Off
Output L1
2
330µH
D1
1N5822
+5V, 1A
Regulated
Output
+
C
OUT
330µF
R2 3.09k
R1 1k
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
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August 2005
1
M9999-082605-B
LM2576
Micrel, Inc.
Ordering Information
Part Number
‡
Standard
RoHS Compliant**
LM2576BT*
†
LM2576-3.3BT
†
LM2576-5.0BT
†
LM2576-12BT
†
LM2576BU*
LM2576-3.3BU
LM2576-5.0BU
LM2576-12BU
LM2576WT*
†
LM2576-3.3WT
†
LM2576-5.0WT
†
LM2576-12WT
†
LM2576WU*
LM2576-3.3WU
LM2576-5.0WU
LM2576-12WU
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
Temperature
Package
TO-220-5
TO-220-5
TO-220-5
TO-220-5
TO-263-5
TO-263-5
TO-263-5
TO-263-5
* Adjustable output regulators.
**RoHS compliant with "hot-melting solder" exemption.
†
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
M9999-082605-B
2
August 2005
LM2576
Micrel, Inc.
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
Electrical Characteristics
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
= 500mA.
LM2576
Symbol
Parameter
Conditions
Typ
Limit
(Note 2)
Units
(Limits)
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS
(Note 3) Test Circuit
Figure 1
V
OUT
Feedback Voltage
V
IN
= 12V , I
LOAD
= 0.5A
V
OUT
= 5V
0.5A
≤
I
LOAD
≤
3A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
V
IN
= 12V, I
LOAD
= 3A, V
OUT
= 5V
V
IN
= 12V , I
LOAD
= 0.5A
V
OUT
= 3.3V
0.5A
≤
I
LOAD
≤
3A, 6V
≤
V
IN
≤
40V
V
OUT
= 3.3V
V
IN
= 12V, I
LOAD
= 3A
V
IN
= 12V , I
LOAD
= 0.5A
V
OUT
= 5V
0.5A
≤
I
LOAD
≤
3A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
V
IN
= 12V, I
LOAD
= 3A
V
IN
= 25V , I
LOAD
= 0.5A
V
OUT
= 12V
0.5A
≤
I
LOAD
≤
3A, 15V
≤
V
IN
≤
40V
V
OUT
= 12V
V
IN
= 25V, I
LOAD
= 3A
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
LM2576
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
LM2576-3.3
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
LM2576-5.0
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
LMLM2576-12
Efficiency
η
August 2005
3
M9999-082605-B
LM2576
Micrel, Inc.
Electrical Characteristics (continued)
LM2576
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
= 3A (Note 4)
(Note 5)
Peak Current, t
ON
≤
3µs (Note 4)
1.4
1.8/2.0
98
93
I
CL
5.8
4.2/3.5
6.9/7.5
2
7.5
30
5
10
Standby Quiescent
Current
Thermal Resistance
ON/OFF Pin = 5V (OFF)
T,U Package, Junction to Ambient (Note 7)
T,U Package, Junction to Ambient (Note 8)
T,U Package, Junction to Case
50
200
65
45
2
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
Quiescent Current
(Note 6)
M9999-082605-B
4
August 2005
京公网安备 11010802033920号
EEWORLD
