No 16-bit references for 16-bit ADCs?

dknguyen · Jan 16, 2007

I was looking at some voltage references for ADCs (at Maxim) and I was wondering something...

There are 16-bit ADCs (avtually, 18-bit ADCsbut are accurate to 16-bits), but the most accurate and stable voltage reference I could find was nowhere near 16-bits. It's variation over temperature was great enough that it would only be noticed by a 12-it ADC or less.

So what is the point of a 16-bit ADC if you can only get a voltage reference that is accurate to 12-bits?

kchriste · Jan 16, 2007

So what is the point of a 16-bit ADC if you can only get a voltage reference that is accurate to 12-bits?

I guess if you were digitizing a waveform with a period much shorter (Such as audio) than the period of ambiant temperature variation.

Optikon · Jan 17, 2007

dknguyen said:
I was looking at some voltage references for ADCs (at Maxim) and I was wondering something...

There are 16-bit ADCs (avtually, 18-bit ADCsbut are accurate to 16-bits), but the most accurate and stable voltage reference I could find was nowhere near 16-bits. It's variation over temperature was great enough that it would only be noticed by a 12-it ADC or less.

So what is the point of a 16-bit ADC if you can only get a voltage reference that is accurate to 12-bits?

Take a look at National LM399 or analog devices. There most certainly are references available to support a true 16 bit system. You won't find them at cheap manufacturers like Maxim.

Analog · Jan 17, 2007

How about a 24 bit ADC?
https://www.cirrus.com/en/products/pro/detail/P1094.html

Actually, you are correct, most references have UNTRIMMED accuracy of <12bits. But read this app note: **broken link removed**

you will hopefully see that the refs, when trimmed, can achieve 16 bits.

dknguyen · Jan 17, 2007

What do you mean by trim? Aren't they trimmed in the factory? And I thought trimming only affects accuracy, not stability?

Optikon · Jan 18, 2007

dknguyen said:
What do you mean by trim? Aren't they trimmed in the factory? And I thought trimming only affects accuracy, not stability?

I think he is referring to "calibrated" within your system.

Sometimes "trimming" (like factory) can affect stability. Take for example, 4 wire precision resistors. Temperature stability can be affected if they are not appropriately trimmed in a balanced fashion.

No 16-bit references for 16-bit ADCs?

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