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Feature #49

3v3 for LPCExpresso

Added by jaap over 5 years ago. Updated over 5 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
Mainboard
Target version:
Start date:
2012-09-30
Due date:
% Done:

100%


Description

The LCPExpresso needs 3v3 power circuit. Can we add that to the board? What is needed for that?

History

#1 Updated by Anonymous over 5 years ago

Good idea - I'm using an MCP1703-3.3V (there are also TO-92 packages, and MCP1702 is equivalent). No extra parts, things are stable as far as I can tell. Note that these regulators don't all use the same pinout.

For the connections, see my recent weblog post.

#2 Updated by jaap over 5 years ago

Added space for MCP1703 and a jumper (to be able to switch between MBED and LPCExpresso).

#3 Updated by jaap over 5 years ago

  • Status changed from New to Resolved

#4 Updated by Anonymous over 5 years ago

Looking at the rev4 board, I'm not sure what package you've used - there's TO-92 through-hole version, which might be more convenient. This regulator does not have ground on the middle pin (it bit me once, just wanted to mention it).

#5 Updated by jaap over 5 years ago

This is the MICROCHIP - MCP1703-3302E/DB in a SOT223 package. Farnell order code: 1627177
Datasheet: http://www.farnell.com/datasheets/77574.pdf

#6 Updated by Anonymous over 5 years ago

FYI, the through-hole version is MC1702, see Farnell # 1331485

#7 Updated by peter over 5 years ago

The MBED is rated at 220mA max
http://mbed.org/users/no2chem/notebook/mbed-power-controlconsumption/

so with the 3v3 to the pololus we may exceed the 250mA max of the 3v3 regulator.
We could search for a 3v3 regulator with higher current rating (500mA) or power the pololus with 5V.
The latter is possible, because the 3V3 logic voltages will still be in the 0/1 range (although they could
be more susceptible to noise). 5V would make interfacing external steppers and RS422 stepper signal easier.

B.t.w. The jumper is not required: if you do not place the component on the board, there is no contact.

#8 Updated by jaap over 5 years ago

  • Tracker changed from Bug to Feature
  • Status changed from Resolved to In Progress

Jumper is placed there so you can still use the board with MBED as well.

Alternative voltage regulator: Farnell order no: 9388338
Specs: http://www.farnell.com/datasheets/71043.pdf

Would that one do the trick? If so, I will adapt the board layout for that one.

#9 Updated by jaap over 5 years ago

  • Status changed from In Progress to Resolved
  • % Done changed from 0 to 100

Now in github...

#10 Updated by jaap over 5 years ago

  • Status changed from Resolved to Closed

Solved in board rev4

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