3563 datasheet(6/10 Pages) UTC

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UTC3563

LINEAR INTEGRATED CIRCUIT

UTC UNISONIC TECHNOLOGIES CO., LTD.

QW-R103-013,B

APPLICATION INFORMATION

DESIGN FORMULA TABLE

CALCULATION

STEP-DOWN

STEP-UP

tON/tOFF

VOUT+VF

VIN(MIN)-VSAT-VOUT

VOUT+VF-VIN(MIN)

VIN(MIN)-VSAT

(tON+tOFF)MAX

1/FMIN

4x10-5tON

IC(SWITCH)

2IOUT(MAX)

tON + tOFF

2IOUT(MAX)(

)

tOFF

0.3/IC(SWITCH)

L(MIN)

VIN(MIN)-VSAT-VOUT

(

) tON(MAX)

IC(SWITCH)

VIN(MIN) - VSAT

(

) tON(MAX)

IC(SWITCH)

IC(SWITCH) (tON+tOFF)

8VRIPPLE(P-P)

IOUT tON

VRIPPLE(P-P)

VSAT : Saturation voltage of the output switch

VF : Forward voltage of the ringback rectifier

The following power supply characteristics must be chosen:

VIN : Norminal input voltage

VOUT : Desired output voltage, VOUT=1.25(1+RB/RA)

IOUT : Desired output current

FMIN : Minimum desired switching frequency at selected values for VIN AND IOUT

VRIPPLE(P-P) : Desired peak-to-peak output ripple voltage. In practice, the calculated value will need to be increased

due to the capacitor 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.

APPLICATION EXAMPLES

Fig. 1 Simplified Battery Charge Circuit for Ni-Cd/Ni-MH Battery

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