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VDD vs VDDA vs VREF on LPC213x

Started by hschew00 February 6, 2012
On Datasheet, all these voltage has nominal at 3.3V
Will I loose ADC's or DAC's accuracy if
1) VDDA is a little higher than VDD due to separate regulators?
2) VREF is a little higher than VDDA if for whatever reason VREF != VDDA?

Hian

An Engineer's Guide to the LPC2100 Series

Hi Hian,

On Mon, 2012-02-06 at 19:38 +0000, hschew00 wrote:
> On Datasheet, all these voltage has nominal at 3.3V
> Will I loose ADC's or DAC's accuracy if
> 1) VDDA is a little higher than VDD due to separate regulators?

No.

> 2) VREF is a little higher than VDDA if for whatever reason VREF != VDDA?

I would always make sure that Vref is the same level as or
a bit lower then Vdda.

The lsb stepsize will be a bit larger but you will
still have 1024 steps between 0V and +Vref.
lsb = +Vref / 1024 (when Vssa = 0V)

roelof