CM2596S

2006/11/27 Rev 1.0

Champion Microelectronic Corporation

Page 10

Feedback Connection

place the output voltage ratio resistors near CM2596S as possible in order to minimize the noise introduction.

Enable

It is required that the

without a resistor in series with it.

Grounding

To maintain output voltage stability, the power ground connections must be low-impedance. For the 5-lead TO-220 and TO-263

style package, both the tab and pin 3 are ground and either connection may be used.

Heatsink and Thermal Consideration

Although the CM2596S requires only a small heatsink for most cases, the following thermal consideration is important for all

operation. With the package thermal resistances θJA and θJC, total power dissipation can be estimated as follows:

When no heatsink is used, the junction temperature rise can be determined by the following:

With the ambient temerpature, the actual junction temperature will be:

If the actual operating junction temperature is out of the safe operating junction temperature (typically 125℃), then a heatsink is

required. When using a heatsink, the junction temperature rise will be reduced by the following:

Also one can see from the above, it is important to choose an heatsink with adequate size and thermal resistance, such that to

maintain the regulator’s junction temperature below the maximum operating temperature.

Layout guideline

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 ground path 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 section for more information.)