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MC34063a Boost issue

Andrew DeMedeiros
Prodigy 10 points
Other Parts Discussed in Thread: MC34063A, TPS61080, TPS61087, TPS61085, TPS61170

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

http://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!

  • 0
    TI__Mastermind 36110 points

    You might try using the suggested values from this website.  http://www.nomad.ee/micros/mc34063a/index.shtml  Another option is to use the TPS61170.  Although the IC price is more expensive, the design is very simple, the external parts cost much less, the overall solution is smaller and cheaper.  If you have a lower input voltage, the TPS61080, TPS61085, or TPS61087 might work.  TI has a very good search tool.  Go to www.ti.com, click on "Power Management" on the left and then enter your electrical specs.  Ease of design, size, and external parts cost often trumps IC cost.