Phase noise transfer functions.pptx

1. Phase noise transfer functions,
ring vco, ring vco layout

2. Input to o/p transfer function VCO to o/p transfer function

3. VCO to o/p transfer function ICP

4. Loop filter noise (R) Power supply noise on VCO

5. Crystal oscillators have good phase noise

6. Ring based
oscillators

7. Power of a ring oscillator
For same frequency, total power independent of N
Refer to noise equation in above slide

8. Phase noise due to divider

9. Razavi LC vco design example !!
Noise due to cross coupled, tail current
source flicker noise for lc vco is not given
in razavi

14. Red are oscn and blue are oscp
capbank
varactors
Gm cell

15. Delay cell

16. Layout of vco • 4,1,3,2 are drawn and capacitively matched
• 8 wires are present vertically
• Pmos small is on the left and nmos (larger) on the right
• All vgnd and vssa connections are symmetric
• Sufficient distance so that wires can run vertically
• Capacitively matched until ac caps

17. Big cap layout • No clock signals on it
• Reference signals ok
• Strong grid
• Have to meet density rules
• Star connection to all important cells
• Ldi/dt not an issue since difference for delay
cells
• What about loop filter capacitor node ?

18. One more arrangement of ring oscillator
Our ring oscillator looked better
Effect of ground bounce

20. Variation is due to supply bounce