PM8903 datasheet(23/34 Pages) STMICROELECTRONICS

Teilenummer	PM8903

Bauteilbeschribung	3 A step-down monolithic switching regulator

PDF	34 Pages

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Hersteller	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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23 / 34 page

PM8903

Application information

Doc ID 022748 Rev 1

23/34

Electrolytic capacitors have a large capacitance to minimize voltage deviation during load

transients while they do not show the same ESR values as the MLCC resulting then in

higher ripple voltages.

A mix between an electrolytic and MLCC capacitor can be used to minimize ripple as well as

reducing voltage deviation in dynamic mode.

The high bandwidth error amplifier of PM8903 and external compensation enables a wide

range of output filter configurations (including all MLCC solutions) and fast transient

response.

6.5

Input capacitors

The input capacitor bank is designed considering mainly the input RMS current that

depends on the output deliverable current (IOUT) and the duty-cycle (D) for the regulation as

follows:

The equation reaches its maximum value, IOUT/2, with D = 0.5. The losses depend on the

input capacitor ESR and, in the worst case, are:

rms

OUT

–

()

⋅

PESR

OUT 2

⁄

()

⋅

PM8903 Datenblatt(PDF) 23 Page - STMicroelectronics