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saurabh_imec

Output voltage levels from the FPGA development boards

Question

Hello, 

I am considering to buy a FPGA board from Digilent. I need to interface it with a chip, designed by me, which has some analog mixed signal circuitry and can have maximum voltage of 900mV.

First, I am not sure as what is the output voltage level from the fpga board. If I understand correctly, it should be 3.3V in Nexys4 DDR Artix-7.

Secondly, how should I regulate the output voltage from the fpga board and make it 900mV to be compatible with my chip ? In this regard, do we something in-built in the board itself ?

Hoping for a prompt response from your side. 

Thanks and regards, 

Saurabh

(saurab.agarwal@gmail.com)

 

 

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2 answers to this question

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Perhaps the safest way would be to use a logic level shifter, such as this PMod.

A cruder way, if you only need to go from 3.3V down to 900 mV is to put an appropriately sized resistor between the two.  For this, I'll say that 1) No, I don't know the value, and 2) on the last project I was on where someone used this technique the result was ... a mess.  So I know it is doable, but I've never done it.

Yours,

Dan

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Hello,

As a note for the PmodLVLSHFT that Dan linked to, it should be of note that the module only supports voltages between 1.8V and 5.5V for conversion. So, I guess in principle you could shift the logic level from 3.3V down to 1.8 V and then nicely use a voltage divider to get the 1.8V down to 900 mV, but as Dan mentions that route can have some issues, especially if your board is sensitive to received voltages.

I guess I'll also clarify that the Nexys 4 DDR does have 3.3V as the output for all of it's general purpose I/O pins. 

Thanks,
JColvin

 

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