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MC34063A: How to calculate the needed NPN transistor to make a step UP with Iout>1,5A

Rafa Exposito
Prodigy 80 points
Part Number: MC34063A
Other Parts Discussed in Thread: TPS61178

Hello!

I have been working with MC34063 and I am trying to do a step Up (boost) from 5V to 14V but the current limit is giving to me some problems,
I need at the output 1A but  without NPN transistor I can't reach 14V 1A at the output. I thinkt this is because at the input, should  be 14*1/5=  2.8A and this current

can't be handler for the internal transistor. I have read the datasheet and it's says that I should use a NPN transistor. There are any note aplication or webpage where explain

how to calculate the performance of the transistor using MC34063?.

Thanks!

  • 0
    TI__Mastermind 46905 points
    you just need to select a NPN with current capability higher than 4A considering the efficiency.

    why select MC34063 for your application? the efficiency will be bad because of the voltage drop in the NPN. I would suggest TPS61178 for your application.
  • 0 in reply to Jasper Li
    Prodigy 80 points

    Dear Jasper,

    I know that there are another IC that are better for my aplication, but they have some "problem", they are SMD, and I have sausage instead fingers and I can't handle it. It's to hard to weld for me. For this reason I am searching somthing with DIP package.

    Thanks to answer!

    I apreciate it!