mc33063a

for 1 A output current , inductor value comes as 0.6 uH which is very low...please help me calculation ..

Archana,

Ignoring voltage losses. A 3V to 28V boost requires a TON/TOFF time of 28:3 (or more).
The output capacitor is only charged during the TOFF time in a boost topology.  
TOFF is 3/31 of the cycle which is about 10% duty cycle. The output current is 1amp (load is 100% duty cycle).
So the average inductor current must be (IOUT / charge duty cycle) 1Amp / 10% = 10 Amps.

This is well beyond the capability of the MC34063A 1.5A switch peak current.

Thanks Ron...I understood your point very well. Please let me know what is maximum output current i can achieve..coz through my calculation , the max output current is 0.05A which is very low to drive my rest of circuit.

Also let me know if any other IC is available which can help me achieve for same specs and output current of 0.75A atleast.

Archana,

Start here, TI power.
http://www.ti.com/lsds/ti/analog/powermanagement/power_portal.page

Fill in the Web bench designer values. VIN min/max , Vout, and IOUT max. Click "start design"
After much delay, two designs will appear for LM3478 and LM3488.
click "open design"