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ID: 881
Case Type: faq
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Family: LatticeXP2

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The LatticeXP2 device does not have a sub-LVDS input type, can I still receive sub-LVDS output signals with the LatticeXP2?

Situation:
An application uses the LatticeXP2 device and needs the sub-LVDS input type.

Solution:
Given that sub-LVDS signaling requires Vod from 100mv (min) to 200mv (max) and Vcm from +0.75v (min) to +1.05v (max), the LatticeXP2 inputs will be compatible with sub-LVDS when setting the input type to either LVDS or HSTL18D.

In some instances, a sub-LVDS receiver is expected to detect signals below the sub-LVDS minimum differential output level of 100mv. Based on characterization tests, the LatticeXP2 LVDS inputs can detect differential signal levels down to approximately 50mv. The guaranteed minimum LVDS input differential specification is 100mV.

Note that the LatticeXP2 does not have on die input termination so given that sub-LVDS requires 100 ohm differential termination at the receiver, you will need to add an external 100 ohm termination resistor across the differential inputs and located physically close to the LatticeXP2 input pins. For best performance, the termination resistor should be either 0402 body size or surface mount resistor packs with minimal length stub traces to the resistor.


You can read more about Sub-LVDS Signaling Using Lattice Devices here:


http://www.latticesemi.com/documents/TN1210.pdf

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