PM6675STR datasheet(30/53 Pages) STMICROELECTRONICS

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Device description

PM6675S

30/53

7.1.4

Mode-of-operation selection

Figure 39.

VSEL and NOSKIP multifunction pin configurations

The PM6675S has been designed to satisfy the widest range of applications. The device is

provided with some multilevel pins which allow the user to choose the appropriate

configuration. The VSEL pin is used to firstly decide between fixed preset or adjustable

(user defined) output voltages.

When the VSEL pin is connected to +5 V, the PM6675S sets the switching section output

voltage to 1.5 V without the need of an external divider.

Applications requiring different output voltages can be managed by PM6675S simply setting

the adjustable mode. Consider that if the VSEL pin voltage is higher than 4 V, the fixed

output mode is selected. When connecting an external divider to the VSEL pin, it is used as

negative input of the error amplifier and the output voltage is given by expression (20).

Equation 20

The output voltage can be set in the range from 0.6 V to 3.3 V.

The NOSKIP is the power saving algorithm selector: if tied to +5 V, the forced-PWM (fixed

frequency) control is performed. If grounded or connected to VREF pin (1.237 V reference

voltage), the Pulse-Skip or Non-Audible Pulse-Skip Modes are respectively selected.

PM6675

NOSKIP

VSEL

VOUT

+5V

VREF

PM6675S

VOUT

ADJ

⋅

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