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 Retrofit BitsyX Rev A supercaps & 5V-only option		  Forum Locked
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sundog

15 Posts
Posted - 09 Jan 2004 :  06:23:33  Show Profile
Hello!

We have three BitsyX boards (Revision A) without Supercaps. We would like to retrofit the boards with supercaps.

Is there any problem with us soldering supercaps directly onto C148 and C149 on the BitsyX board? Or are additional parts required?

What type of Supercap should we use?

Thanks
-Cameron

akidder

1519 Posts
Posted - 09 Jan 2004 :  10:57:04  Show Profile
Sure, it's fine to add the caps yourself. However, since we can't vouch for the rework or parts, we won't be able to warranty the board(s) if they are damaged in the process.

If you want to proceed, you can stuff 3.3F 2.5V supercaps (e.g. Cooper B1020-2R5335) for C188 and C189.

Make sure that the charge/discharge components are populated on your systems (we usually stuff them, even when the supercaps aren't). Locations of the components on rev C BitsyX systems are shown below (they're probably the same locations as rev A). The component locations are in (X,Y) format in 1/1000 inch (mils) relative to the mounting hole at the corner of the BitsyX where J10 and J3 meet.

  D20  (325, 1250) BOTTOM 1A Schottky diode (e.g Vishay Liteon or Diodes Inc B120)
  R263 (575, 1250) BOTTOM 22 ohms
  R309 (475, 1250) BOTTOM 22 ohms
  R273 (175, 1375) BOTTOM 470k
  R274 (175,  950) TOP    470k
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sundog

15 Posts
Posted - 09 Jan 2004 :  18:58:00  Show Profile
That is fantastic! I checked our BitsyX boards. We have all of the charge/discharge parts populated as you described above. We only need to populate the supercaps. Thanks!

I just spoke with a co-worker. We have another retro-fit question.

We have a clean, efficient 5V supply in our system. We are interested in bypassing the BitsyX 5V regulator, and apply our own 5V directly to VBATT_POS.

The BitsyX User's Manual, page 37, section 5.3.1 describes a factory option to bypass the 5V regulator. Is it possible to retro-fit our boards with this bypass? What parts do we need to add/remove to implement this?

-Cameron
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akidder

1519 Posts
Posted - 12 Jan 2004 :  10:24:22  Show Profile

Changing to 5V-only is a trickier endeavour, especially because we've found that power supplies are a regular source of trouble in many designs. If there's any way that you can take advantage of using the higher-voltage DC inputs, I think you'll find the results to be better.

I'd be glad to give you information similar to what I gave you above, but off-line. Just drop me a line.

p.s. For the subscribers out there, please forgive the spastic, premature Return key on those last, now-deleted posts.
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