ST1S14 datasheet(15/46 Pages) STMICROELECTRONICS

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ST1S14

Additional features and limitations

5.2

Minimum output voltage over VIN range

The minimum regulated output voltage at a given input voltage is limited by the minimum

conduction time of the power element, that is 90 nsec typ. for the ST1S14:

Equation 1

which is plotted in Figure 14. The reference of the embedded error amplifier (1.22 V) sets

the minimum VO_SET at low VIN.

Figure 8. VO_MIN over input voltage range

Figure 8 shows the minimum output voltage over input voltage range to have constant

switching activity and a predictable output voltage ripple.

The regulator can, however, regulate the minimum input voltage over the entire input

voltage range but, given the 90 ns minimum conduction time of the power element, it skips

some pulses to keep the output voltage in regulation when Equation 1 is not satisfied.

This operation is not recommended at the nominal input voltage of the application mainly

because it affects the output voltage ripple, but it is generally accepted during a line

transient event.

O_MIN VIN

()

MIN

⋅

ON_MIN

----------------------

⋅

90ns

1.18

μs

------------------

⋅

ST1S14 데이터시트(PDF) 15 Page - STMicroelectronics