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As I understand it FPGAs are flexible "digital" circuits, that let you design and build and rebuild a digital circuit.

It might sound naive or silly but I was wondering if there are FPGAs or other "flexible" technologies that also make analog components available to the designer, like amplifiers, or A/D or D/A or transceivers or even more simple components?

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    \$\begingroup\$ I heard about something that would do this a couple years ago. I have no clue what the name of them is though. \$\endgroup\$ – Kellenjb Jan 23 '12 at 15:56
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    \$\begingroup\$ A past not-quite-duplicate question: electronics.stackexchange.com/questions/24315/ \$\endgroup\$ – The Photon Jan 23 '12 at 16:41
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    \$\begingroup\$ I remember it being called FPAA(Field Programmable Analog Array) \$\endgroup\$ – Matt Mar 6 '12 at 22:08
  • \$\begingroup\$ There is some specific vendor other than Altera and Xilinx which does have ADC and DAC built into their FPGAs themself. Besides this like Matt said we also have Fild Programmable Analog arrays. \$\endgroup\$ – quantum231 Sep 16 '14 at 22:03
  • \$\begingroup\$ Not quite what you're asking for but interesting nonetheless: zrna.org \$\endgroup\$ – tonys Aug 2 at 2:51
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I've used a product line called the Electronically Programmable Analog Circuit (EPAC), probably more than ten years ago by now, which claimed to be the analog equivalent of an FPGA, and Cypress has for years produced a line called the PSoC (Programmable System On Chip) which incorporates a switchable arrays of both analog and digital circuitry. Note that in both cases the devices have a moderately small number of functional blocks (3 to 24 or so in the case of the PSoC) with somewhat limited routing options, rather than providing hundreds or thousands of blocks with enough interconnects to allow essentially arbitrary routing.

One reason that analog FPGA's don't offer anywhere near the design flexibility of digital devices is that even if one passes a digital signal through dozens or hundreds of levels of routing and logic circuitry, each of which has a 10dB signal-to-noise ratio (SNR), meaning there's 1/3 as much noise as signal, the resulting signal can be clean. By contrast, getting a clean signal from an analog device requires that every stage the signal goes through must be clean. The more complex the routing, the more difficult it is to avoid picking up stray signals.

In applications that aren't too demanding, having a small amount of analog circuitry combined into a chip can be useful. For example, I've designed a music box which uses a PSoC to drive a piezo speaker directly; the PSoC includes a DAC, a fourth-order low-pass filter, and output amplifier. It wouldn't have been hard to use a separate chip to do the filtering and amplification, but using the PSoC avoided the need for an extra chip.

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  • \$\begingroup\$ Would be nice if there were some sort of reference for this. No company? No product line? No part number? No articles about it? Can't find anything useful by searching for "electronically programmable IC" \$\endgroup\$ – krb686 Sep 16 '14 at 16:42
  • \$\begingroup\$ Try "Electronically Programmable Analog Circuit"? I just did a quick Google and it seems I'd gotten the name slightly wring (fixed above). \$\endgroup\$ – supercat Sep 16 '14 at 17:10
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    \$\begingroup\$ @krb686 Cypress PSoC \$\endgroup\$ – Tut Sep 16 '14 at 17:28
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This is the first shot from Google; seems to be a very new technology, and only a few manufacturers are producing them.

I don't know if the analog part is flexible as the FPGA block, but for sure it combines the features.

UPDATE: In the Actel there is only an integrated ADC (ASIC) and a fixed number of analog inputs, depending on the model.

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  • \$\begingroup\$ So basically, these are FPGAs that have some specialized analog component in them for very specific use? (sorry I don't know what PLLs are). \$\endgroup\$ – Ali Jan 23 '12 at 16:06
  • \$\begingroup\$ Oh, just saw the Kintex-7 , very cool. So these are called mixed signal FPGA. \$\endgroup\$ – Ali Jan 23 '12 at 16:09
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    \$\begingroup\$ Anadigm also make FPAAs. \$\endgroup\$ – MikeJ-UK Jan 23 '12 at 16:12
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    \$\begingroup\$ @ThePhoton shouldn't you move the comment below the question? \$\endgroup\$ – clabacchio Jan 23 '12 at 16:36
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Years ago, Lattice had a series called ispPAC with different configurations of in-system-programmable analog blocks. More CPLD-level complexity than FPGA-level. These are all now obsolete.

I suspect there is simply too much variation in requirements across different analog applications to allow one chip to "do it all". For example, in one design you might need a ADC input buffer with 16-bit accuracy; in another you might need only want 8-bit accuracy and want to keep the cost as low as possible. There's no way a general-purpose programmable block could simultaneously suit both of those applications.

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Triad Semiconductor, www.TriadSemi.com, makes via configurable analog and mixed signal arrays (known as VCAs). These VCAs are single-mask configurable and not field programmable. This does mean that there is a mask charge and processing time associated with a VCA.

VCA fabrication costs are significantly lower than a traditional full-custom mixed-signal ASIC. VCA fabrication, package and test can be as short as four weeks compared to 4-6 months for traditional ASICs.

Field Programmable Analog suffers from serious noise and performance issues because the routing fabric contains a large number of transistors.

Via Configurable Analog uses vias as the interconnect resource. These vias are a standard part of a full-custom design but in a via-configurable analog array only the vias change to configure a design onto a given VCA.

Vias are very high-performance, low resistance and low-noise. Via configured arrays have full-custom mixed-signal IC performance with much lower development costs and fabrication times.

I posted an article on Why Field Programmable Analog is a Little Too Programmable on PlanetAnalog.com.

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  • \$\begingroup\$ This person is with ViaDesigner a maker of SW that can be used to program ViaASIC's from TriadSemi. It is not clear that there is necessarily a relationship there, nor is he promoting his product - in the interests of disclosure. \$\endgroup\$ – placeholder Mar 14 '13 at 18:04
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Your microcontroller may have some analog components. For example, the STM32F303x(A|C) has 4 opamps (§3.15) and 7 comparators (§3.16).

There's a very limited amount of customizablity--for example, the opamps' outputs can be connected to the microcontroller's ADC, but they can't be connected to an output pin or to the input of an internal comparator. However, the comparators's outputs can be connected to an output pin. The full interconnect matrix can be found in §3.8.

I'm also sure that microcontrollers by other vendors have a similar set of configurable peripherals--but I've been working with the STM32 series recently, so I'm familiar with their design.

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    \$\begingroup\$ Indeed, some other manufacturers have very configurable mixed-signal peripherals in their MCU portfolio. Check MSP430FR235x, for example, and their "Smart Analog Combo" block. \$\endgroup\$ – dim Jul 1 at 10:58
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You may check out Microsemi SmartFusion at;

http://www.microsemi.com/products/fpga-soc/soc-fpga/smartfusion

These have FPGA, uP, and programmable analog all on one chip. I used these in a school project and utilized all those parts sucessfully.

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Anadigm makes a FPAA or field programmable analog array. http://www.anadigm.com/fpaa.asp Their designer software makes it trivial to set up a filter or many other analog functions. Servenger makes a low cost <400USD development board that supports the Anadigm designer software. PAM 5002R http://www.servenger.com/

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