On Mon, 3 Jan 2005 18:11:04 +0000, Wookey <wookey@aleph1.co.uk> wrote:

> +++ Wookey [05-01-03 16:19 +0000]:
>> OK, I've got a supply of MAX 604 Chips.
>>
>> Looking at the schematic suggests that I should just add one of these to
>> U22,

Yep.

and that U22 is right next to the Xilinx and the other MAX604 chip

Yep.

>> right?

Yep.

>> However whilst this chip seems to be an option on it's own (here:
>> http://balloonboard.org/hardware/buildoptions.html ) it looks like I  
>> also
>> need to add a couple of links (R12 and R36) _or_ the MAX 894 switch for  
>> 5V
>> power to make it anywhere other than the 3V regulator - right?
>
> OK - more perusal shows that it's more subtle than this

More subtle as in 'not true' :) It's as simple as it looks, honestly.
Your continued planning is fine - if you're not using those rails, feel  
free to fit neither the switch nor the bypass resistors.

Note that _all_ the 3V power will go through that poor little regulator,  
which has a relatively strictly enforced 500mA current limit. If you're  
planning to feed CF cards, you'll need to organise some extra power round  
the side (balancing another regulator on top of U22, and feeding its  
output pin onto the CF power should do the trick)
This is all fixed in the doomed 2.06 and the imminent 3.00 revision.

Steve