Full CMOS 0.18um tech to achieve the LVPECL I/O interface

[jxzhang]

lvpecl spec

Hello buddy,
How can I design a system w/ LVPECL I/O by CMOS 0.18um (TSMC) process,
1.8V rail? or I just can use 3.3V supply that is really a 0.35um process?

 

[Vamsi Mocherla]

Re: Full CMOS 0.18um tech to achieve the LVPECL I/O interfac

Hey dude,

I am not clear on your question?Do you mean to design a circuit for I/O? Or do you want to design the core circuit(say for some application) with LVPECL I/Os. If latter is the case, you can stick to the core voltage offfered by your process......

If you have to design an I/O you will have to design level shifters for stepping up and stepping down.

I hope I am clear on this issue.....Please retort back with any other questions

 

[jxzhang]

Re: Full CMOS 0.18um tech to achieve the LVPECL I/O interfac

Sorry the question described was not clear.
I'm going to design a CDR system by CMOS 0.18um process(TSMC), not Bipolar
The input and output (data streams and clock) spec. is LVPECL.
That is, Vcm=2V and Vpp=800mV
Can I use the rail 1.8V for core circuit with some I/O level shifter to achieve LVPECL I/O or use the rail 3.3V for all system? Which one is better? single supply?

 

[Vamsi Mocherla]

Re: Full CMOS 0.18um tech to achieve the LVPECL I/O interfac

Well, you can definately use the Dual supply mode in case you want to go for low power design. Also, since your Vpp is only 800 mV, you can have a VCM level of 0.9 V for the core. And you can use the level shifters and DC bias of 2 V for the I/O. Of course, you can do the DC blocking for the input signal and rebias it for 0.9V VCM.

I hope that this answer is clear

 

[andy2000a]

Re: Full CMOS 0.18um tech to achieve the LVPECL I/O interfac

I ever design LVDS I/O .. it like LVPECL ..also have Vcm ..
many type I/O can be use

1. use OPA buffer control Vmc=2v and use series Resistor for limit Voh
becuase LVDS have output impedance require ..
and I/O use 3.3v

2. direct use I/O buffer like CMOS invert and use 1.8v or 3.3v

if you use series resistor on invert output , you will find large volt_drop on it
and let your I/O keep 800mv ..

you can search other hi speed IO , like LVDS USB2 LDT(hyper transport)
many type can be use .. use resistor is simple , but resistor will have large
current and need 3.3v power , for good is resistor have good match in
corner model than use MOS Rds