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The layout of switching DC-DC converters is very important to minimize noise and 
interference. Power-generating portions of the layout are the main cause of noise and so 
high switching current loop areas should be kept as small as possible and lead lengths as 
short as possible.

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. An layout 
example is provided in 

.

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 pick-up noise.

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

Conduction losses due to the not insignificant R

DSON

, which are equal to:

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

OUT

 and V

IN

, but in practice it is substantially higher than this value to 

compensate for the losses in the overall application. For this reason, the switching losses 
related to the R

DSON

 increases compared to an ideal case.

A5970AD

P

ON

R

DSON

I

OUT







2

D



=