LM2576TV-012G ON Semiconductor, LM2576TV-012G Datasheet - Page 19

• Manufacturer Part Number: LM2576TV-012G
• Description: IC REG SW 3A 12V STEPDWN TO220-5
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of LM2576TV-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 (Bent and Staggered 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

0.7 A to the output when the input voltage is 12 V or higher.
At lighter loads the minimum input voltage required drops
to approximately 4.7 V, because the buck−boost regulator
topology can produce an output voltage that, in its absolute
value, is either greater or less than the input voltage.
are higher than in the standard buck converter topology, the
available output current is lower.
require a larger amount of startup input current, even for
light loads. This may overload an input power source with
a current limit less than 5.0 A.
least 2.0 ms or more. The actual time depends on the output
voltage and size of the output capacitor.
this inverting regulator topology, the use of a delayed startup
or an undervoltage lockout circuit is recommended.
can charge up to a higher voltage before the switch−mode
regulator begins to operate.
supplied by the input capacitor C
situations, the delayed startup or the undervoltage lockout
features could be very useful. A delayed startup circuit
applied to a buck−boost converter is shown in Figure 27,
Figure 33 in the “Undervoltage Lockout” section describes
an undervoltage lockout feature for the same converter
topology.
Design Recommendations:
than the buck converter and so a different design procedure
has to be used to select the inductor L1 or the output
capacitor C
normally required for buck converter designs. Low input
voltages or high output currents require a large value output
capacitor (in the range of thousands of mF).
inverting converter design is between 68 mH and 220 mH. To
select an inductor with an appropriate current rating, the
inductor peak current has to be calculated.
current:
This circuit configuration is able to deliver approximately
Since the switch currents in this buck−boost configuration
This type of buck−boost inverting regulator can also
Such an amount of input startup current is needed for at
Because of the relatively high startup currents required by
Using a delayed startup arrangement, the input capacitor
The high input current needed for startup is now partially
It has been already mentioned above, that in some
The inverting regulator operates in a different manner
The output capacitor values must be larger than what is
The recommended range of inductor values for the
The following formula is used to obtain the peak inductor
out
.
in
.
http://onsemi.com
LM2576
19
5.0 V
conditions, the worst case occurs when V
100 mF
pin requires some level shifting techniques. This is caused
by the fact, that the ground pin of the converter IC is no
longer at ground. Now, the ON/OFF pin threshold voltage
(1.3 V approximately) has to be related to the negative
output voltage level. There are many different possible shut
down methods, two of them are shown in Figures 28 and 29.
where t on +
12 V to 25 V
Unregulated
DC Input
Figure 28. Inverting Buck−Boost Regulator Shutdown
/50 V
Under normal continuous inductor current operating
With the inverting configuration, the use of the ON/OFF
0
C
in
NOTE: This picture does not show the complete circuit.
On
Figure 27. Inverting Buck−Boost Regulator
I
0.1 mF
peak
Off
C1
Shutdown
Input
+V
+V
[
Circuit Using an Optocoupler
V
in
1
in
47 k
R1
in
470
R3
I
Load
|V
with Delayed startup
5
) |V
LM2576−12
O
ON/OFF
R2
47 k
|
(V
O
C
100 mF
V
in
in
|
in
x 1.0
MOC8101
3
) |V
f osc
47 k
GN
D
R1
4
Output
2
Feedback
O
, and f osc + 52 kHz.
+V
|)
in
1
)
D1
1N5822
5
in
68 mH
V
L1
LM2576−XX
is minimal.
in
ON/OFF
R2
47 k
2L 1
−12 V @ 700 m A
x t on
Regulated
Output
C
2200 mF
/16 V
3
out
GN
D
−V
out