MC33463 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

MFG CO.

MC33463

VARIABLE FREQUENCY MICROPOWER DC–to–DC CONVERTER

Motorola => Freescale 

MC33463

Calculation

ton

L

IL(avg)

IL(pk)

Vripple(pp)

Figure 20. Design Equations

Step–Down

Step–Up

D

ƪ ƫ tton

fosc

* * (Vin Vsat VO)

(2IO)

D

fosc

t (n)(Vin)2(ton)

PO

IO

* * (Vin Vsat VO)(ton)

L

1

2

2

ȧȱȲǒ Ǔ ȳȴȧ ) DIL

1

16foscCO

(ESR)2

Iin

* (Vin Vsat)(ton)

L

[ (ton)(IO)

(CO)

Flyback

D

fosc

t (n)(Vin)2(ton)

PO

Iin

* (Vin Vsat)(ton)

L

[ (ton)(IO)

(CO)

The following converter design characteristics must be chosen:

Vin – Nominal Operating dc input voltage

VO – Desired dc output voltage

IO – Desired dc output current

Vripple(pp) – Desired peak–to–peak output ripple voltage. For best performance the ripple voltage should be kept to a low value since it will directly

affect line and load regulation. Capacitor CO should be a low equivalent series resistance (ESR) electrolytic designed for switching regulator

applications.

NOTE: 1. Vsat – Saturation voltage of the switching transistor.

n – Estimated circuit efficiency.

MOTOROLA ANALOG IC DEVICE DATA

11

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