Old 05-03-2012, 07:05 AM #1
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Default Help with my buck-boost driver design

So it's time for me to try to build a smps driver. I've been working on a design with the tps63020 and lt6106, but I'm still not sure if I've got the math and schematic right. So if you look at my schematic, from looking at the data sheets for the two ICs, I think the equation would be
Iout=FB*(Rin/Rout)/Rsense.

Is this equation correct?

Looking at the datasheet I think the FB voltage for the tps63020 is .5V and picking .01 for Rsense and and 100 for Rin, and I out as 1 amp I get.

1=.5(100/Rout)/.01 which if I'm not being dumb gives me 5k

Also, how does my schematic look? It's not simulating in TINA, I keep getting the error "operating point not found". Do you think R1 is necesary? And is my placement of C3 good?

One more thing I'm having trouble calculating the inductance I need. The equation in the datasheet uses Ipeak in the equation to calculate min inductance, but when I plug in the peak current I want, I keep getting a negative number. Is Ipeak the peak current or peak current ripple?

Sorry for so many questions, just want to make sure everything's good before I make any boards.
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Old 05-03-2012, 07:31 AM #2
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Default Re: Help with my buck-boost driver design

I would suggest just trying it and seeing if it works.
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Old 05-03-2012, 03:55 PM #3
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Default Re: Help with my buck-boost driver design

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Originally Posted by Wolfman29 View Post
I would suggest just trying it and seeing if it works.
It takes me a while to make boards though. I'm just looking to see if anyone who has experience with this kind of thing can tell me if everything checks out before I do make some pcbs.
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Old 05-04-2012, 06:46 AM #4
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Default Re: Help with my buck-boost driver design

Thank you. One question, what is the zener for? Why would you want the FB connected to the V+ like that?
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Old 05-04-2012, 04:25 PM #5
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Default Re: Help with my buck-boost driver design

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Originally Posted by sk8aseth View Post
Thank you. One question, what is the zener for? Why would you want the FB connected to the V+ like that?
You can find the answer in this thread
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Old 05-05-2012, 05:32 AM #6
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Default Re: Help with my buck-boost driver design

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Originally Posted by laserluke View Post
You can find the answer in this thread
Thanks that thread is very useful and the use of the zener is very clever.
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