LM2597 datasheet(21/48 Pages) TI

21 / 48 page

LM2597, LM2597HV

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SNVS119C – MARCH 1998 – REVISED APRIL 2013

Select R1 to be approximately 1 kΩ, use a 1% resistor for best stability.

Component Values shown are for VIN = 20V,

VOUT = 10V, ILOAD = 500 mA.

CIN

— 68

μF, 35V, Aluminum Electrolytic Nichicon “PL Series”

COUT — 120 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”

— 1A, 30V Schottky Rectifier, 1N5818

— 150

μH, L19

— 1 k

Ω, 1%

— 7.15k, 1%

CFF — 3.3 nF, See Application Information

Typical Values

CSS — 0.1 μF

CDELAY — 0.1 μF

RPULL UP — 4.7k

*For output voltages between 4V and 20V

Figure 31. Adjustable Output Voltage Versions

As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring

inductance can generate voltage transients which can cause problems. For minimal inductance and ground

loops, the wires indicated by heavy lines should be wide printed circuit traces and should be kept as short

as possible. For best results, external components should be located as close to the switcher lC as possible

using ground plane construction or single point grounding.

If open core inductors are used, special care must be taken as to the location and positioning of this type of

inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and COUT wiring can cause

problems.

When using the adjustable version, special care must be taken as to the location of the feedback resistors and

the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor,

especially an open core type of inductor. (See Application Information for more information.)

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LM2597 Datasheet(PDF) 21 Page - Texas Instruments