R5973AD datasheet(24/38 Pages) STMICROELECTRONICS

24 / 38 page

Application information

R5973AD

24/38

DocID027027 Rev 1

High impedance paths (in particular the feedback connections) are susceptible to

interference, so they should be as far as possible from the high current paths. A layout

example is provided in Figure 13.

The input and output loops are minimized to avoid radiation and high frequency resonance

problems. The feedback pin connections to the external divider are very close to the device

to avoid pickup noise. Another important issue is the ground plane of the board. Since the

package has an exposed pad, it is very important to connect it to an extended ground plane

in order to reduce the thermal resistance junction to ambient.

Figure 13. Layout example

8.3

Thermal considerations

The dissipated power of the device is tied to three different sources:



Conduction losses due to the not insignificant RDSON, which are equal to:

Equation 22

Where D is the duty cycle of the application. Note that the duty cycle is theoretically given by

the ratio between VOUT and VIN, but in practice it is substantially higher than this value to

PON

RDSON IOUT





R5973AD Datasheet(PDF) 24 Page - STMicroelectronics