Difference between an ADC and an AFE - Page 1
Forum section: electronics / projects

author: migsantiago
author_rank: Frequent Contributor
timestamp: October 09, 2010, 01:46:57 pm
content: HelloRecently, Microchip has been releasing new datasheets with new PICs and other ICs. There are some new analog-to-digital converters which feature Delta-Sigma architectures which reach resolutions up to 24 bits.There are some PIC18 that include this new analog converters and are aimed to Energy measurements.Code:http://twitter.com/#!/MicrochipTech/status/25034688338My question is, why are they calling these new analog converters "Analog Front End"? What makes them different to any Analog-To-Digital Converter (ADC) in the market? What's the difference between them?http://bit.ly/bmqDQlhttp://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en544175The only one I've spotted is that the so called AFE's are using an embedded PGA into the PIC... but that's all I got. There are so many 24bit ADCs out there that use normal SAR or Delta-Sigma architectures and are not called AFE.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 10, 2010, 08:46:23 am
content: I'd interpred AFE as meaning that there is hardware to help implement a software-based ADC, as opposed to a conventional ADC where all the work is done by hardware.

author: hans
author_rank: Super Contributor
timestamp: October 10, 2010, 09:09:07 am
content: This is analog frontend because it includes the full signal condition block on a chip die. You just put the differential signal from any sensor in it, and it amplifies the difference, filters it and proccesses it. If you'd do this manually, you need a extra couple of opamps and an A/D for better resolution. Yet though, if you do your best, you can easily beat the specs of this chip I think. Looking at the performance, it can do gains up to 32 times and gain 14.89 Effective resolution if you oversample 256x times (that's 4 bits extra due to that).It's basically just an A/D with a bit of monolithic analog hardware in front of it. Saves board space and cost, if the performance figures fit your bill.

author: Hypernova
author_rank: Unknown
timestamp: October 10, 2010, 11:56:57 am
content: Quote from: hans on October 10, 2010, 09:09:07 amThe gain part isn't special, ATXMEGA's ADC has a preamp that does 64X and 200Ksps (official spec claims 2Msps). The Microchip one is special more from the opamp that sits in front of the delta-sigma which allows it to take high impedance signals and like you said the filtering.

author: migsantiago
author_rank: Frequent Contributor
timestamp: October 10, 2010, 02:08:32 pm
content: Got it!So an AFE is an ADC with all the signal acquisition and conditioning that a normal ADC doesn't have.Thanks guys.

author: Zad
author_rank: Super Contributor
timestamp: October 10, 2010, 06:34:21 pm
content: On-die 24-bit ADCs? That has to be a triumph of marketing over engineering. Getting even 20 true bits is difficult on a standalone converter with good layout and components, so I can't see it making better than 14 or so. I guess they are doing it because they can and can shout about it in the advertising.

author: migsantiago
author_rank: Frequent Contributor
timestamp: October 29, 2010, 01:51:41 pm
content: Quote from: Zad on October 10, 2010, 06:34:21 pmThey are selling a 4-layered demo board featuring the MCP3901.