Ring oscillator as a test structure

[Prithvee]

Hi,

Can someone briefly explain me how the ring oscillator serves the function of a test structure in predicting the frequency of operation of a Chip?

Thanks.

 

[mikersia]

typically a number of ring oscillator (RO) types are implemented in test chip: ROs with inverters, buffers, gates (nand, nor,...); RO with different fanouts (FO=1, FO=4,...). RO self oscillating frequency at different conditions (i.e. PVT) give a most timing information dealing with library characterization/verification.