X

0

Q

© 2012 Exar Corporation

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Rev. 1.2.2

Total input voltage ripple is the sum of the above:

ESR

Cin

Tot

V

V

V

∆

+

∆

=

∆

Power MOSFETs Selection

Selecting MOSFETs with lower Rdson reduces conduction losses at the expense of increased

switching losses. A simplified expression for conduction losses is given by:

in

out

dson

out

cond

V

V

R

I

P

⋅

⋅

=

2

MOSFET’s junction temperature can be estimated from:

ambient

thja

cond

j

T

R

P

T

+

=

2

thermal resistance from junction to ambient.

“XRP77XX: Extending the MOSFET Gate Drive Conductors”.

See ANP-31 “PowerXR Configuration and Programming” for details of the register map and other

programming information.