AN2559 datasheet(10/35 Pages) STMICROELECTRONICS

10 / 35 page

PM6680A block

AN2559

10/35

construction of passive components (inductors or ceramic capacitors). In PWM mode the

converter maintains a constant switching frequency independently on the load.

The FSEL pin the PM6680A dedicated for operating frequency setting is connected to GND.

This means that the switching frequency of the VCORE branch is 200 kHz and switching

frequency of VI/O is 300 kHz.

Figure 7.

Skip mode connector

3.0.3

Step-down parts

The PM6680A is a dual step-down controller and drives two step-down converters. The

schematic of both channels are almost identical, with only a few small differences. Since

each channel is for a different output power, the main difference is in the components’

values. Figure 8 displays the output connector polarities of the PM6680A section.

Table 3.

Skip mode connector jumper settings

Jumper settings

Function

Skip mode at light load.

No Audible Skip mode at light load (frequency never drops below 30 kHz).

PWM mode. Constant frequency even at light or zero load.

Sk ip

PW M

Au d io

Sk ip

PW M

Au d io

Sk ip

PW M

Au d io

Sk ip

P W M

Au d io

Sk ip

P W M

Au d io

Sk ip

P W M

Au d io

Sk ip

PW M

Au d io

Sk ip

PW M

Au d io

Sk ip

PW M

Au d io

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