LM2586

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SNVS121D – MAY 1996 – REVISED APRIL 2013

Figure 59. Circuit Board Layout

CIRCUIT LAYOUT GUIDELINES

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

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

keep the length of the leads and traces as short as possible. Use single point grounding or ground plane

construction for best results. Separate the signal grounds from the power grounds (as indicated in Figure 59).

When using the Adjustable version, physically locate the programming resistors as near the regulator IC as

possible, to keep the sensitive feedback wiring short.

HEAT SINK/THERMAL CONSIDERATIONS

In many cases, a heat sink is not required to keep the LM2586 junction temperature within the allowed operating

temperature range. For each application, to determine whether or not a heat sink will be required, the following

must be identified:

1) Maximum ambient temperature (in the application).

2) Maximum regulator power dissipation (in the application).

3) Maximum allowed junction temperature (125°C for the LM2586). For a safe, conservative design, a

temperature approximately 15°C cooler than the maximum junction temperature should be selected (110°C).

4) LM2586 package thermal resistances

where

•

•

•

N is the transformer turns ratio, D is the duty cycle

•

flyback regulators)

(7)

The duty cycle is given by:

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