AN2093 - APPLICATION NOTE

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3. INDUCTOR CHOICE

The ST1S03 is a PWM voltage regulator with a typical working frequency of 1.5MHz. The very high

frequency allows the use of small inductor values. The device is able to work with a minimum of 1µH

inductor. We suggest using 3.3µH or higher values in order to cover all the parameters specified in the

datasheet. Another important parameter to take into account in the inductor choice is the saturation

current. Normally the device does not exceed a peak current of 2.3A @ Vin=5V.

4. SCHOTTKY DIODE

During the Toff the current in the inductor can continue to flow thanks to the schottky diode. It is very

important the use of a diode with a very low threshold, in order to have high efficiency, and with a good

current capability. In our application good results are obtained using the STPS2L30A diode.

In some applications, where the switching noise must be reduced, it could be useful to add a snubber

circuit in parallel with the schottky diode. If necessary, we suggest to connect a 10

Ω resistor in series with

a 680pF capacitor.

5. CONCLUSIONS

The device can be used in all the applications where a low supply voltage, starting from 0.8V, is needed.

The low inductor and capacitors value allows the use of the ST1S03 in all the boards where space saving

and power dissipation control is recommended. The high frequency makes the device compatible with

the new HDD generation, where the rotation plate is 7200rpm or 10000rpm.