PM6686 datasheet(42/50 Pages) STMICROELECTRONICS

42 / 50 page

Diode selection

PM6686

42/50

Doc ID 15281 Rev 4

Diode selection

11.1

Freewheeling diode

A rectifier across the low-side MOSFET is recommended. The rectifier works as a voltage

clamp across the synchronous rectifier and reduces the negative inductor swing during the

dead time between turning the high-side MOSFET off and the synchronous rectifier on. It

can increase the efficiency of the switching section, since it reduces the low-side switch

losses. A Schottky diode is suitable for its low forward voltage drop (0.3 V). The diode

reverse voltage must be greater than the maximum input voltage. A minimum recovery

reverse charge is preferable. Below there is a list of some Schottky diode manufacturers.

11.2

Charge pump diode

The charge pump capacitors are fed by the current supplied by LGATE1 (output of the low-

side driver for the section 1). Dual in package diodes, in series configuration, could be used

to reduce the area occupation.

Table 20.

Schottky diode manufacturer

Manufacturer

Series

Forward voltage

(V)

Rated reverse

voltage (V)

Reverse current

(

μA)

STPS1L30M

0.34

0.00039

STPS1L20M

0.37

0.000075

Table 21.

Schottky diode manufacturer

Manufacturer

Series

Forward voltage

(V)

Rated reverse

voltage (V)

Max forward

current (A)

BAT54S

0.24

0.3

BAR43A

0.35

0.1

BAS69-04

0.35

0.01

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