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Visitor
Visitor
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Registered: ‎05-16-2019

Artix-7 LVCMOS1.8 standard

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Xilinx's specs said the LVCOMS 1.8V is following JEDEC standard. The VOL is 0.25 * VDD maximum and VOH is  0.75 * VDD minimum. So for 1.8V VDD, the result is VOL = 0.45V max and VOH = 1.35V min.

 

I try to use Artix-7 to interface with ISSI SRAM 64WV204816A, Accordint their spec, their chip has

VIH = 1.4V min and VIL = 0.4V max

Doesn't look like they are compatible.

 

Another example is Cypress FX3. Their spec is

VIH = Vcc - 0.4 =  1.4V min and VIL = Vcc * 0.25 = 0.45V max

Still not compatible

 

Can I still use Artix-7 to interface with these ICs?

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Xilinx Employee
Xilinx Employee
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Registered: ‎06-06-2018

Hi @tonywu2000 ,

Your SRAM and CYPRESS device doesn't have same spec.

Difference i found is VIL for Cypress is 0.45 Max and for SRAM is 0.4Max.

 

LVCMOS1.8 VOH is well within VIH of Cypress and LVCMOS1.8 VOL is well within/equal to VIL to Cypress. Hence interface will happen.

 

Please try IBIS Simulation for double confirmation. Because Board physics (like Trace impedance, SI issues on board etc) might effect successful interface of LVCMOS and Cypress device.

Regards,
Deepak D N
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Xilinx Employee
Xilinx Employee
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Registered: ‎06-06-2018

Hi @tonywu2000 ,

Can I still use Artix-7 to interface with these ICs?

>> Seeing at your calculation of VOH,VIH,VOL and VIL Levels you cant interface with SRAM. But you can interface with Cypress FX3.

If you want to be sure, Please perform IBIS Simulation, which will confirm you whether you can interface or not. To perform IBIS Simulation, you need IBIS Models. For more information on how to generate IBIS Models refer this AR#50957 

Regards,
Deepak D N
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Visitor
Visitor
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Registered: ‎05-16-2019

Hi Deepak,

 

Thanks for your reply. I am wondering why the Xilinx's LVCOM1.8 doesn't seem to be compatible with other 1.8V device? And the two devices that I mentioned have very similar specs. Which one is the industrial standard? Can you get comments from your engineer?

 

Tony

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Xilinx Employee
Xilinx Employee
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Registered: ‎06-06-2018

Hi @tonywu2000 ,

Your SRAM and CYPRESS device doesn't have same spec.

Difference i found is VIL for Cypress is 0.45 Max and for SRAM is 0.4Max.

 

LVCMOS1.8 VOH is well within VIH of Cypress and LVCMOS1.8 VOL is well within/equal to VIL to Cypress. Hence interface will happen.

 

Please try IBIS Simulation for double confirmation. Because Board physics (like Trace impedance, SI issues on board etc) might effect successful interface of LVCMOS and Cypress device.

Regards,
Deepak D N
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