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Design >> Analog Design >> cheap programmable divider
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Message started by vivkr on Mar 28^th, 2008, 8:15am

Title: cheap programmable divider
Post by vivkr on Mar 28^th, 2008, 8:15am

Hi,

I was wondering if there was a good way to make a cheap programmable resistive divider, say 6-8 bit?

Thanks
Vivek

Title: Re: cheap programmable divider
Post by thechopper on Mar 30^th, 2008, 3:01pm

Hi Vivek,

I think the trade off between achieving such resolution and making a cheap resistor divider is (and I'm sure you know it) the R-2R ladder structure. You would need 2^N taps (N= number of bits) and your divider would only have unit cells of size R. Making a straightforward resistor divider by using equally sized resistor for each tap would require much more parallel/series combination for such resolution than the ones you need for the R-2R structure.

Hope this helps
Tosei.

Title: Re: cheap programmable divider
Post by vivkr on Mar 31^st, 2008, 11:08pm

Hi Tosei,

Thanks for your reply. Indeed, the basic tradeoff is clear. I need to see if I can use an R-2R ladder. I
think this will be a problem for me because I need to keep the overall ladder resistance more or less
constant (not too much variation). Perhaps I can try some variation on this one.

Vivek