LVDS Driver Voltage specification

Hi,

I am designing a programmable IO Buffer that support LVDS standard (with many other standards).

I am kind of confused with the voltage specification of LVDS 2.5V. In many doc/datasheets, it is written the VOD (output differential voltage) should be within 250-450 mV with a typical value of 350mV. In other words, the drivers should provide 2.5mA - 4.5mA for 100ohms termination as the standard requires.

My question is that: What if the driver provides (for whatever reason) more than 4.5 mA, therefore VODmax exceeds 450mV? Let's assume the driver provides 9mA, therefore VOD is 900mV across 100ohms termination resistor. We can't anymore say that the interface standard is LVDS?

My understanding is the following: The maximum voltage swing at the output buffer is limited in order to guarantee enough common-mode noise margin at receiver end. However, if I assume two chips communicating in the same PCB board with few inches of distance, does the noise requirement remain still valid?

Thank you for your help/answers.

Excess drive is not a problem until you get past the
supply rails, provided that the difference voltage is
above spec VIHmin/VILmax.

The standard is still LVDS. Your compliance to it, is
out of spec in the posited case. But for functionality
you need to be looking to the receiver's input specs
and not just the transmitter, by the numbers.

Thank you for your reply, that is what I tought as well!