V

= V

OUT

REF

1 +

(

(

R2

R1

LM2575

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SLVS569F – JANUARY 2005 – REVISED AUGUST 2015

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The limited component count and internal frequency compensation makes the LM2575 easy use. Output voltage

is set by two external resistors.

where

•

VREF = 1.23 V

(1)

8.2 Typical Application

Figure 11. Buck Regulator With User Programmable Output Voltage

8.2.1 Design Requirements

Output voltage is set by R1 and R2. Output voltage must be between VREF and (VIN[minimum] – VSAT) × Duty

Cycle [maximum].

VSAT maximum and duty cycle maximum are specified in the Electrical Characteristics table.

8.2.2 Detailed Design Procedure

8.2.2.1 Input Capacitor (CIN)

For stability concerns, an input bypass capacitor (electrolytic, CIN ≥ 47 μF) must be located as close as possible

to the regulator. For operating temperatures below –25°C, CIN may need to be larger in value. In addition,

because 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.

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