PM6686 datasheet(41/50 Pages) STMICROELECTRONICS

41 / 50 page

PM6686

Application information

Doc ID 15281 Rev 4

41/50

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

Equation 17

Maximum conduction losses occur at the maximum input voltage:

Equation 18

Choose a synchronous rectifier with low RDS(on). When high-side MOSFET turns on, the

fast variation of the phase node voltage can bring up even the low-side gate through its

gate-drain capacitance CRSS, causing cross-conduction problems. Choose a low-side

MOSFETs that minimizes the ratio CRSS/CGS (CGS = CISS - CRSS).

Below there is a list of some possible low-side MOSFETs.

Dual N-channel MOSFETs can be used in applications with a maximum output current of

about 3 A. Below there is a list of some MOSFETs manufacturers.

Table 17.

High-side MOSFET manufacturer

Manufacturer

Type

Gate charge (nC)

RDS(on) (mΩ) Rated reverse voltage (V)

STS12NH3LL

STS17NH3LL

Table 18.

Low-side MOSFET manufacturer

Manufacturer

Type

RDS(on) (mΩ)

Rated reverse voltage

(V)

STS17NF3LL

5.5

0.047

STS25NH3LL

3.5

0.011

Table 19.

Dual MOSFET manufacturer

Manufacturer

Type

RDS(on) (mΩ)

Gate charge

(nC)

Rated reverse voltage

(V)

STS8DNH3LL

STS4DNF60L

conduction

DLowSide

LOAD

max

OUT

DSon

conduction

(max)

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

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