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Visitor
Visitor
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Registered: ‎06-02-2016

Interfacing with custom ASIC assistance

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Hi guys,

I am currently working on a project that requires me to generate some control signals to a custom ASIC. I am new to the FPGA world and I have some really straightforward questions, and would be glad if you could help me out.

First, is there a way to have the power banks low reference voltage to a level different than ground? For instance, I want to have a bank that goes from 0 to 1.2V and another one that would have a low reference at 1.2V and go all the way to 2.4V (or near values).

Second, is there any place where I can find the DC characteristics of the IO standards? I need to make sure the FPGA's outputs stay in a range that won't damage the ASIC chip.

I know this is not really Spartan related but I decided to pick that one to get started with this kind of concepts since this family seems to be simpler. So if there is any other alternatives that are unrelated to the Spartan family I would help me as well.

Best

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Teacher
Teacher
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Registered: ‎03-31-2012

Re: Interfacing with custom ASIC assistance

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1) I think what you need is a DAC.

 

3) To me it doesn't make sense to do manual soldering while you are working on an ASIC. How much do you value your time? One can get laser stencils for around a $100. If you really need a custom board (ie one with an extension bus is not enough) I'd design it, get it manufactured and assembled professionally. In the end, you would be saving time (and some money too probably).

 

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Teacher
Teacher
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Registered: ‎03-31-2012

Re: Interfacing with custom ASIC assistance

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1) I am not sure what you mean by 1.2V reference. Do you mean a signal which has one state at 1.2V wrt ground and another state at 2.4V wrt ground?

2) I think the information you're looking for is in this datasheet: http://www.xilinx.com/support/documentation/data_sheets/ds162.pdf

3) My choice for spartan alternative would be artix family.
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Registered: ‎06-02-2016

Re: Interfacing with custom ASIC assistance

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muzaffer,

Thank you for your reply.

1) What I meant was I need a output that has a 0 logic i.e. at ~0V and a 1 logic at ~1.2V and another output that has a 0 logic at ~1.2V and a 1 logic at ~2.4V. So I was wondering if I could offset the ground of one of the power banks or even if there is any possible solution at all.

I have been doing some research and maybe I would need an external logic level translator, any thoughts?

3) The Artix was my first option, but it might not work because of packaging (I need to hand solder the FPGA to the PCB, so I need a package like the QFP).
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Teacher
Teacher
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Registered: ‎03-31-2012

Re: Interfacing with custom ASIC assistance

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1) I think what you need is a DAC.

 

3) To me it doesn't make sense to do manual soldering while you are working on an ASIC. How much do you value your time? One can get laser stencils for around a $100. If you really need a custom board (ie one with an extension bus is not enough) I'd design it, get it manufactured and assembled professionally. In the end, you would be saving time (and some money too probably).

 

- Please mark the Answer as "Accept as solution" if information provided is helpful.
Give Kudos to a post which you think is helpful and reply oriented.

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Advisor
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Registered: ‎04-26-2015

Re: Interfacing with custom ASIC assistance

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@roquetto

 

(1) Sounds like you need an optocoupler or something similar. That way power/ground for the input and output are totally separated and can be just about whatever you want.

 

(2) Could you give us a bit more detail on the requirements? I've often found that using an off-the-shelf FPGA module (eg. those made by Enclustra) greatly simplifies the design, since they've already dealt with all of the complex FPGA power supplies (often the module can provide power to external devices too), all of the BGA soldering, and all of the high-speed PCB layout. The user only has to solder a surface-mount socket to accept the module, which is easy to do by hand. The downsides, of course, are that there's less flexibility on board layout, and you may end up with features you don't need (RAM, flash, etc).

 

 

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Visitor
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Registered: ‎06-02-2016

Re: Interfacing with custom ASIC assistance

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@u4223374

 

Thanks for stopping by. What I needed basically was to generate some control signals to/read the outputs of the ASIC, which is basically a bunch of analog devices. The thing is the voltage specifications for those are also a little bit unusual. In summary, I needed a FPGA (to generate and read the control signals I need) that could interface with the chip. So I was trying to figure out how I could tweak the I/Os to get what I wanted and maybe try to centralize all I could in the FPGA. I guess this kind of questions raised since I was/am not really familiar with FPGAs overall.

As @muzaffer suggested, I am definitely going to need some external circuitry to do what I want to do. So basically now I am going to add external ADCs/DACs and some more circuitry to my PCB to actually get to where I want, which was probably the obvious way to do it.

 

Nevertheless, I really appreciate your guys' help. I'm still getting started on the FPGA world and all this content you guys generate is awesome.

Thanks!

 

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