LM2576T-012G ON Semiconductor, LM2576T-012G Datasheet - Page 18

IC REG SW 3A 12V STEPDWN TO220-5

LM2576T-012G

Manufacturer Part Number
LM2576T-012G
Description
IC REG SW 3A 12V STEPDWN TO220-5
Manufacturer
ON Semiconductor
Type
Step-Down (Buck)r
Datasheet

Specifications of LM2576T-012G

Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
12V
Current - Output
3A
Frequency - Switching
52kHz
Voltage - Input
7 ~ 40 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Through Hole
Package / Case
TO-220-5 (Straight Leads)
Output Voltage
12 V
Output Current
3 A
Input Voltage
4.75 V to 40 V
Switching Frequency
52 KHz
Operating Temperature Range
- 40 C to + 125 C
Mounting Style
Through Hole
Duty Cycle (max)
98 %
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LM2576T-012G
Manufacturer:
ON Semiconductor
Quantity:
2 000
beyond approximately 6.0 in
heat
improvements are needed, double sided or multilayer PC
boards with large copper areas should be considered. In
order to achieve the best thermal performance, it is highly
recommended to use wide copper traces as well as large
areas of copper in the printed circuit board layout. The only
exception to this is the OUTPUT (switch) pin, which should
not have large areas of copper (see page 8 ‘PCB Layout
Guideline’).
Thermal Analysis and Design
whether or not a heatsink will be required. First determine:
1. P
2. T
3. T
4. R
5. R
(Refer to Maximum Ratings on page 2 of this data sheet or
R
total power dissipated by the LM2576:
where d is the duty cycle and for buck converter
I
V
V
I
turn−off can be neglected if proper type catch diode is used.
Packages Not on a Heatsink (Free−Standing)
the junction temperature can be determined by the following
expression:
where (R
caused by the dissipated power and T
ambient temperature.
Q
Load
qJC
in
O
The following procedure must be performed to determine
The following formula is to calculate the approximate
The dynamic switching losses during turn−on and
For a free−standing application when no heatsink is used,
D(max)
A(max
J(max)
qJC
qJA
and R
(quiescent current) and V
LM2576 data sheet,
is minimum input voltage applied,
is the regulator output voltage,
is the load current.
dissipation
qJA
)
qJA
)(P
P
maximum regulator power dissipation in the
application.
maximum ambient temperature in the
application.
maximum allowed junction temperature
(125°C for the LM2576). For a conservative
design, the maximum junction temperature
should not exceed 110°C to assure safe
operation. For every additional +10°C
temperature rise that the junction must
withstand, the estimated operating lifetime
of the component is halved.
package thermal resistance junction−case.
package thermal resistance junction−ambient.
D
values).
D
= (V
) represents the junction temperature rise
T
J
significantly.
in
d +
= (R
x I
Q
t on
qJA
T
) + d x I
2
) (P
+
(4000 mm
sat
V
V
D
) + T
O
in
can be found in the
Load
,
If
A
x V
A
2
) will not improve
further
is the maximum
sat
thermal
http://onsemi.com
LM2576
18
Packages on a Heatsink
the selected safe operating junction temperature determined
in step 3, than a heatsink is required. The junction
temperature will be calculated as follows:
where
selected safe operating junction temperature, then a larger
heatsink is required.
Some Aspects That can Influence Thermal Design
the junction temperature rise numbers are all approximate,
and there are many factors that will affect these numbers,
such as PC board size, shape, thickness, physical position,
location, board temperature, as well as whether the
surrounding air is moving or still.
area, copper thickness, single− or double−sided, multilayer
board, the amount of solder on the board or even color of the
traces.
board can also influence its effectiveness to dissipate the heat.
12 to 40 V
Unregulated
DC Input
ADDITIONAL APPLICATIONS
Inverting Regulator
is shown in Figure 26. This circuit converts a positive input
voltage to a negative output voltage with a common ground
by bootstrapping the regulators ground to the negative
output voltage. By grounding the feedback pin, the regulator
senses the inverted output voltage and regulates it.
−12 V output. The maximum input voltage in this case
cannot exceed +28 V because the maximum voltage
appearing across the regulator is the absolute sum of the
input and output voltages and this must be limited to a
maximum of 40 V.
If the actual operating junction temperature is greater than
If the actual operating temperature is greater than the
It should be noted that the package thermal resistance and
Other factors are trace width, total printed circuit copper
The size, quantity and spacing of other components on the
An inverting buck−boost regulator using the LM2576−12
In this example the LM2576−12 is used to generate a
100 mF
Figure 26. Inverting Buck−Boost Develops −12 V
C
in
R
R
R
qJC
qCS
qSA
T
+V
J
in
1
is the thermal resistance junction−case,
is the thermal resistance case−heatsink,
= P
is the thermal resistance heatsink−ambient.
3
D
LM2576−12
GN
D
(R
qJA
+ R
5
qCS
ON/OFF
+ R
4
Output
2
Feedback
qSA
D1
1N5822
68 mH
) + T
L1
A
−12 V @ 0.7 A
Regulated
Output
C
2200 mF
out

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