UNIVERSAL DC/DC CONVERTER

2007-1-25

10/10

FSP34063

DESIGN FORMULA TABLE

Calculation

Step-Up

Step-Down

Voltage-Inverting

(min)

(min)

OUT

F

in

in

sat

VV

V

VV

+−

−

(min)

OUT

F

in

sat

OUT

VV

VV

V

+

−−

OUT

F

in

sat

VV

VV

+

−

1/f

1/f

1/f

1

on

off

on

off

tt

t

t

+

+

1

on

off

on

off

tt

t

t

+

+

1

on

off

on

off

tt

t

t

+

+

()

on

off

off

tt

t

+−

()

on

off

off

tt

t

+

−

()

on

off

off

tt

t

+−

5

4.0 10

on

t

−

×

5

4.0 10

on

t

−

×

5

4.0 10

on

t

−

×

(max)

2(

/

1)

out

on

off

It

t

+

(max)

2

out

I

(max)

2(

/

1)

out

on

off

It

t

+

()

0.3 /

PK switch

I

()

0.3 /

PKswitch

I

()

0.3 /

PKswitch

I

(min)

(max)

()

in

sat

on

pk switch

VV

t

I

−

(min)

(max)

()

in

sat

out

on

pk switch

VV

V

t

I

−

−

(min)

(max)

()

in

sat

on

pk switch

VV

t

I

−

Co

()

9

out on

ripple pp

I t

V

()

)

()

(

8

pk switch

off

on

ripple pp

I

tt

V

+

()

9

out on

ripple pp

I t

V

Vsat=Saturation voltage of the output switch.

VF=Forward voltage drop of the output rectifier.

The following power supply characteristics must be chosen:

Vin-Norminal input voltage

Vout-Desired output voltage, |vout|=1.25(1+ R2/R1)

Iout-Desired output current

fmin-Minimum desired output switching frequency at the selected values of Vin and Io

Vripple(pp)-Desired peak-to-peak output ripple voltage, In practice, the calculated capacitor value will need to be

increased due to its equivalent series resistance and board layout. The ripple voltage should be kept to a low value

since it will directly affect the line and load regulation.