MC34063EC View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

MC34063EC

DC/DC converter control circuits

STMicroelectronics 

MC34063AB - MC34063AC - MC34063EB - MC34063EC

Typical application circuit

Table 12. Calculation

Parameter

Step-Up

(Discontinuous mode)

Step-Down

(Continuous mode)

Voltage Inverting

(Discontinuous mode)

ton/toff

(ton + toff) max

CT

IPK(switch)

RSC

CO

L(min)

--O----U---T-----+-----V----F----–-----V----I--N---(--m-----i

VIN(min) – Vsat

1/fmin

4.5x10-5ton

2Iout(max)[(ton/toff)+1]

0.3/IPK(switch)

--------I--o---u---t-t--o---n--------

Vripple(p – p)

V--I-N----(--m----i--n---)---–----V----s---a---t

IPK(switch)

×

ton(mi

-----------V----O----U----T-----+----V-----F--------------

N(min) – Vsat – VOU

1/fmin

4.5x10-5ton

2Iout(max)

0.3/IPK(switch)

I--P----K---(--s---w----i-t--c--h---)--(---t--o---n----+-----t-o---f--f--)

8Vripple(p – p)

N---(--m----i--n---)---–----V----s---a---t---–----V-----o---u--t

IPK(switch)

×

ton(

--V----O----U----T------+-----V----F-

VIN – Vsat

1/fmin

4.5x10-5ton

2Iout(max)[(ton/toff)+1]

0.3/IPK(switch)

--------I--o---u---t-t--o---n--------

Vripple(p – p)

V--I-N----(--m----i--n---)---–----V----s---a---t

IPK(switch)

×

ton(mi

Note:

VSAT = Saturation voltage of the output switch

VF = Forward voltage drop of the output rectifier

The following power supply characteristics must be chosen:

VIN = Nominal 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 = Desired peak to peak output ripple voltage. In practice, the calculated capacitor

value will and 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.

13/23

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