MPZ2012S221A datasheet(43/56 Pages) STMICROELECTRONICS

Part #	MPZ2012S221A

Description	38 V, 10 W synchronous iso-buck converter for isolated applications

PDF	56 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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10.4

Output capacitors selection

Primary output capacitor

As in a standard buck converter, the primary output capacitor is involved in:

•

Determining the output voltage ripple

•

Supporting load transient

•

Loop stability, by setting one pole and one zero in the transfer function

Considering the output voltage ripple requirement, the primary output capacitance should be selected according

to the following equation:

COUT_pri=

ΔIpri

8∙fSW∙ΔVOUT_pri−ESR∙ΔIpri

(46)

Normally, MLCC capacitors are the best choice for the output capacitor, therefore the ESR contribution is

negligible and Eq. (46) can be simplified.

Secondary output capacitor

The secondary output capacitor supplies the secondary output load current during the tON (when diode D1 is

reverse biased) and its value defines the secondary output voltage ripple (ΔVOUT).

COUT_sec= IOUT_sec∙D

ΔVOUT_sec∙fSW

(47)

L6983I

Output capacitors selection

DS14040 - Rev 1

page 43/56

MPZ2012S221A Datasheet(PDF) 43 Page - STMicroelectronics