Dual power supply for LVDS Tx...

[bharatsmile2007]

advantages of dual power supply

Hi all,

what would be the need for LVDS Tx having dual power supply?

i saw an LVDS IP which says :

3.3V / 1.8V dual power supply..

would any one explain me the advantage/disadvantages of dual power supply in LVDS Tx...?

Thanks

 

[erikl]

dual supply lvds

Probably "either | or" is meant, i.e. works with 3.3V or (down to) 1.8V.

 

[PaloAlto]

lvds 1.8v to 3.3v

In many CMOS processes, the digital part works at 1.8v but there is also 3.3V for analog mainly.

LVDS standard requires 1.2V common mode and 0.4 diff. That is quite complicated to get with 1.8V +-10%. That's why the input of the lvds tx is 1.8V (digital) but later it is shifted up to the 3.3V domain

 

[bharatsmile2007]

advantages and disadvantages of dual power supply

Thanks PaloAlto...

Thanks erikl...

 

[bharatsmile2007]

Hi PaloAlto,

What would be the common mode voltage for Sub-LVDS?

Thanks a lot...

 

[PaloAlto]

I'm sorry. I do not know those specs

 

[marxelus]

I've read some papers about this.
You can change the two p-mos of the h-bridge for two current sources to have the same current and Vcm with less vdd.
But it's only necessary for vdd<2.5 V