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”
D1 — 1A, 30V Schottky Rectifier, 1N5818
L1 — 150 μH, L19
R1 — 1 kΩ, 1%
R2 — 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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