MC34063a Step-Up Converter issue

[tanky321]

mc34063a

Hi,

Im trying to go from 12V to 15V but I seem to be having an issue. I have the inverting setup giving me -15V and it works fine, but I cant get the +15V to work. In this data sheet

https://focus.ti.com/lit/ds/symlink/mc34063a.pdf

on page 6 there is the circuit im using. I dont know about the value of the resistor connected to pin 8, so I used a 220Ω. My values that I calculated are listed below.

L=25uH
Diode= Schottkey Vf=0.5V
Rsense=100mΩ R1=1k pot R2=10k
CT=300pF Co=5uF


Any ideas?


Thanks!

 

[CMOS]

mc34063a design tool

Try this online design tool
**broken link removed**

 

[tanky321]

mc34063a stepup

I tried it, i get pretty much the same values, so it didnt help me too much.

Anything else?

 

[eSilviu]

Re: mc34063a stepup

I tried it, i get pretty much the same values, so it didnt help me too much.

Anything else?

output diode shouldn't be inversed to obtain +15V? just my 2 cents, after seeing the schematic for 2 sec.