do people include bandgap current reference in PLL design?

[qqpei]

pll band gap

I am recently reading some ph.d dissertation about PLL design. Seems very few mentioned the current reference design in charge pump. Do they use some kind of standard circuits or they use some external current reference when measuring their circuits ?

 

[khouly]

bandgap current reference

in real chips , we need a good current reference , so there is a bandgap on real pll or any chip

in phd "acadimic" laborotry use , there r good current source that u use
so u dont need to design one

khouly

 

[mr_chip]

bandgap reference pll

Normally there's a bandgap reference on a chip which is further distributed to all blocks, including PLL. So generally speaking, bandgap is not a part of PLL design.

 

[Y.C Park]

Re: do people include bandgap current reference in PLL desig

HI All

I had experienced of PLL Design in CMOS technology.
I used Bandgap reference and V-I converter .
And the other design is self biased circuit like a Constant-Gm Bias.
But I think BGR+V-I Converter has more good performance.
( Temperature, Power variation and process )

Thank you.

 

[cmosekv]

Re: do people include bandgap current reference in PLL desig

Bandgap is usually not part of PLL. Bandgap provides a stable voltage reference not current reference. Current references are generated using bandgap voltage. I wouldn't even put bandgap too close to PLL for the reason of noise concerns.

 

[yibinhsieh]

Re: do people include bandgap current reference in PLL desig

The chargepump current in PLL can have large variation. So if your requirement is not so critical, You can just use external R to generate the current.

Yibin.

 

[zouwanghui]

Re: do people include bandgap current reference in PLL desig

Bandgap is usually not part of PLL. Bandgap provides a stable voltage reference not current reference. Current references are generated using bandgap voltage. I wouldn't even put bandgap too close to PLL for the reason of noise concerns.

PLL has analog part and digital part, just put bandgap away from digital part, that's enough