Lpc2000

Ez,

First off can I recommend that you consider using the 2138 in place of 
the 2106. I started off with the 2106 and the only reason I would use it 
now is because it has more RAM and possibly because it's a smaller 
package. The 2138 has it's own 1.8V regulator and as you already have a 
3.3V supply it means you can do without the size and cost of additional 
regulators.

To answer your question though, yes, you can connect the 1.8V regulator 
in series with the 3.3V without problems.

I am not sure about the FTDI question however, though there shouldn't 
really be a problem as these types of chips are designed to be operated 
this way. Personally, I find the CP2102 devices far easier to use as 
they truly are a SCFF* single-chip USB-UART bridge.

*Small, Cheap, Fast, and Flawless (as far as I can tell).

*Peter*


Ezequiel L. Aceto wrote:
> Hello
>
> I'm designing a little device with the LPC2106. I have worked with
> this MCU but never in the situation that I wanted to work now.
> I need to power the LPC2106 only with 3.3V, and also attach a FTDI232
> USB (to program the LPC, and also as a virtual Comm for the PC).
>
> One of the problems comes with the power supply for the LPC, can I
> give 3.3V directly to the MCU, and connect a regulator to the 3.3V
> line to generate 1.8V?  I always connected 3.3V and 1.8V "in parallel"
> as a 5V supply feed them, but now I only have 3.3V and don't know if
> there is a problem to give first (for a few mSec) 3.3V and then 1.8V.
>
> And last but not least, I need to power the FTDI with 3.3V, which is
> not a problem, but I will only have 5V when connected to the USB, then
> I will only have 3.3V. So I will connect and power VCCIO with 3.3V but
> the other voltage sources will "float" when the device is not
> connected. Might this cause any problem?