LM2575T-15 National Semiconductor, LM2575T-15 Datasheet - Page 5

• Manufacturer Part Number: LM2575T-15
• Description: Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2575T-15

• No. Of Pins: 5
• Output Current: 1A
• Peak Reflow Compatible (260 C): No
• Output Voltage: 15V
• Termination Type: Through Hole
• Supply Voltage Max: 40V
• Leaded Process Compatible: No
• Mounting Type: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Layout Guidelines
With any switching regulator, circuit layout plays an important role in circuit performance. Wiring and parasitic
inductances, as well as stray capacitances, are subjected to rapidly switching currents, which can result in
unwanted voltage transients. To minimize inductance and ground loops, the length of the leads indicated by
heavy lines (see
ground-plane construction. For the same reasons, the two programming resistors used in the adjustable version
should be located as close as possible to the regulator to keep the sensitive feedback wiring short.
Input Capacitor (C
For stability concerns, an input bypass capacitor (electrolytic, C
possible to the regulator. For operating temperatures below –25 C, C
addition, since most electrolytic capacitors have decreasing capacitances and increasing ESR as temperature
drops, adding a ceramic or solid tantalum capacitor in parallel increases the stability in cold temperatures.
To extend the capacitor operating lifetime, the capacitor RMS ripple current rating should be:
I
Output Capacitor (C
For both loop stability and filtering of ripple voltage, an output capacitor also is required, again in close proximity
to the regulator. For best performance, low-ESR aluminum electrolytics are recommended, although standard
aluminum electrolytics may be adequate for some applications. Based on the following equation:
Output Ripple Voltage = (ESR of C
C,RMS
V
Where
V
R1 = 2 kW
R2 = 6.12 kW
www.ti.com
OUT
REF
u 1.2(
Unregulated
7-V to 60-V
DC Input
t
t
= 1.23 V
= V
T
T
on
on
+
+
REF
t
T
on
V
(| V
(1 + R2/R1) = 5 V
) I
V
OUT
IN
LOAD
OUT
Figure
| V
{buck regulator}, and
OUT
| ) V
, where:
IN
|
+
)
OUT
1) should be minimized. Optimal results can be achieved by single-point grounding or by
IN
)
)
{buck−boost regulator}
C
100 F
IN
5, 12, 13 GND
+V
Figure 1. Test Circuit and Layout Guidelines
Adjustable Output Voltage Versions
16
IN
OUT
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
)
APPLICATION INFORMATION
(inductor ripple current)
LM2575
(ADJ)
9 ON/OFF
FEEDBACK
7
OUTPUT
3
IN
D1
11DQ06
330 H
L1
47 F) needs to be located as close as
SLVS569E – JANUARY 2005 – REVISED JANUARY 2006
IN
may need to be larger in value. In
+
C
330 F
OUT
R2
R1
LM2575
V
OUT
L
O
A
D
5