i try to get stable +12/-12v by using double mc34063, one is step down converter and other is inverter .. i have checked every thing on a breadbord for both configuration and i got +12 and -12v seperately. but when i designed both of configurtion on a board and tested, at the negative converter circuit , becoming overheating at coil 8L1) and the capacitor (c6) is exploded and the mc34063 (U6) is burned... i checked many things and checked all connection, it looks there is no problem. my opinion what the both circuit is in interaction, but how i could not understand... i am not so experted on electronic circuits.. could any body please help me and give advices?? thanks in advance.. .

 

Not sure what current you are pulling from the -12v... but the datasheet doesn't mention negative conversion.

I would use the trusty max 865... They need a charge pump to generate negative voltages... I use the old 7660 for my -5v but it only outputs 50mA (ish)

Sorry I have just re-read the datasheet... It must be down to stability... it does say 4.5v to 6 to output -12v

 

Not sure what current you are pulling from the -12v... but the datasheet doesn't mention negative conversion.

I would use the trusty max 865... They need a charge pump to generate negative voltages... I use the old 7660 for my -5v but it only outputs 50mA (ish)

Sorry I have just re-read the datasheet... It must be down to stability... it does say 4.5v to 6 to output -12v

When i tested there was no load. .. without any load i got troubles.. i checked any short circuit and i could not see problem. Now i will dismount all parts related to +12v circuit and will test again. Thanks