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Visitor samchen
Visitor
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Registered: ‎05-15-2018

VRN & VRP

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I am using ZYNQ-7000 PL HP interface,

I config Bank#33, #34, #35 to SSTL12_T_DCI,

I connect VRP, VRN with 40 ohms resistor to GND and VCCO,

I would like to know the ODT (on-die-termination) value when I set it to input mode.

Thanks!

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Moderator
Moderator
1,068 Views
Registered: ‎04-18-2011

Re: VRN & VRP

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Hi @samchen

 

Please don't use a resistor value this low. 

If you look at the IO UG. 

SSTL needs the reference resistor to be 2x the Z0(line impedance)

 

80ohm reference for 40ohm traces. 

100ohm reference for 50ohm traces and so on. 

 

I doubt the DCI would have the range to calibrate down to 40ohms. 

 

 

sstldci.JPG

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Moderator
Moderator
1,069 Views
Registered: ‎04-18-2011

Re: VRN & VRP

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Hi @samchen

 

Please don't use a resistor value this low. 

If you look at the IO UG. 

SSTL needs the reference resistor to be 2x the Z0(line impedance)

 

80ohm reference for 40ohm traces. 

100ohm reference for 50ohm traces and so on. 

 

I doubt the DCI would have the range to calibrate down to 40ohms. 

 

 

sstldci.JPG

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Newbie westec2
Newbie
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Registered: ‎09-07-2018

Re: VRN & VRP

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Hi, does this also apply to Zynq 7000 PS LPDDR2, using HSUL 1.2V?  From what I read in UG933, Rvrn and Rvrp should be exactly equal to the line impedance. 

 

More importantly: what is the Rvrn/vrp value that was used to create the IBIS model?  The IBIS model is just called HSUL_12_DCI_S_HP or HSUL_12_DCI_F_HP (slow and fast.)  So, the user does not know the impedance.

 

Thanks!

Joseph

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Moderator
Moderator
730 Views
Registered: ‎04-18-2011

Re: VRN & VRP

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HSUL is different...The reference resistor is calibrating the output impedance only. 

 

The reply above was for SSTL15 DCI... 

 

i expect that the PS DDR HSUL12 driver model is for 40ohm traces

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