topic Re: What are the LPC553x Voltage Reference Selection Options? in LPC Microcontrollers

What are the LPC553x Voltage Reference Selection Options?

BrightFuture — Tue, 05 Dec 2023 19:15:43 GMT

What are the LPC553x Voltage Reference Selection Options? I am referring specifically to the LPC5534JBD100K.

LPC553x Reference Manual lists three options for REFSEL. What do these options correspond to?

Here is my assumption. Is this correct?
00 - Option 1 = Vref0 = VDDA
01 - Option 2 = Vref1 = VREF_OUT
10 - Option 3 = Vref2 = VREFP

Reference 1: "Figure 265. Analog subsystem connectivity" in the LPC553x Reference Manual.
Reference 2: REFSEL in the in the ADC Configuration Register (CFG)

Re: What are the LPC553x Voltage Reference Selection Options?

_Leo_ — Tue, 05 Dec 2023 21:52:48 GMT

Thank you so much for your interest in our products and for using our community.

I noticed that you have another similar case, so I will follow up on this last one that I mention.

Have a nice day!

Re: What are the LPC553x Voltage Reference Selection Options?

danielholala — Thu, 18 Jan 2024 09:24:21 GMT

Sorry, your assumptions are incorrect. To quote the LPC553x reference manual:

Re: What are the LPC553x Voltage Reference Selection Options?

xiangjun_rong — Thu, 18 Jan 2024 09:27:46 GMT

Hi,

Pls refer to the ppt page screenshot.

CFG[REFSEL]=0, the ADC reference voltage is the external pad VREFP voltage.

CFG[REFSEL]=1, the ADC reference voltage is the VREF_OUT voltage, in the case, you have to initialize VREF_OUT module. Pls refer to Chapter 52 Voltage Reference (VREF)

CFG[REFSEL]=2, the ADC reference voltage is the VDDA pin power supply voltage.

Because the UM of LPC553x is not clear, per external customer requirement, I post it here.

XiangJun Rong

Re: What are the LPC553x Voltage Reference Selection Options?

danielholala — Fri, 16 Feb 2024 14:14:10 GMT

Just in case anybody thinks this is also true for DAC, don't be fooled, NXP wants us to read the manual properly.

The DAC reference options "inverted", that is they are exactly as in @BrightFuture's original posting:

It would have been too nice if there had been a pattern here regardings reference selection.