PM6680ATR datasheet(33/48 Pages) STMICROELECTRONICS

33 / 48 page

PM6680A

Design guidelines

33/48

9.5

Power MOSFETS

Logic-level MOSFETs are recommended, since low side and high side gate drivers are

In notebook applications, power management efficiency is a high level requirement. The

power dissipation on the power switches becomes an important factor in switching

selections. Losses of high-side and low-side MOSFETs depend on their working conditions.

The power dissipation of the high-side MOSFET is given by:

Equation 18

Maximum conduction losses are approximately:

Equation 19

where RDSon is the drain-source on resistance of the high side MOSFET.

Switching losses are approximately:

Equation 20

where ton and toff are the switching times of the turn on and turn off phases of the MOSFET.

As general rule, high side MOSFETs with low gate charge are recommended, in order to

minimize driver losses.

Below there is a list of possible choices for the high side MOSFET.

The power dissipation of the low side MOSFET is given by:

Equation 21

Maximum conduction losses occur at the maximum input voltage:

Table 13.

High side MOSFET manufacturer

Manufacturer

Type

Gate charge (nC)

Rated reverse voltage (V)

STS5NF60L

switching

conduction

DHighSide

LOAD

min

OUT

DSon

conduction

(max)

)

(max)

(

)

(max)

(

off

LOAD

switching

∆

−

conduction

DLowSide

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