EECS 713 Project Instructor: Prof. Allen Presented by: Chen Jia

Definition  Signal integrity (SI): is a set of measures of the quality of an electrical signal. We expect the signal can response time series, electrical level correspondingly.  Was not always a case in earlier days. Challenges for designers  Concerns: why, what, when, and how

Why  When SI happens, the noise margin requirement will not be satisfied – logic errors, false switching, system collapses, etc.  In high speed digital system, we are expecting a string that contains bits H(1) and L(0). A continuous voltage waveform. Receivers sample the signal by generating the rising and falling edge of the signal.

A Failure in catching rising or falling edge, or misreading an ambiguous logic state may result in an incomplete data transmission or even a failure of transmission. Settle down to non-ambiguous before receiver kicks in

We want to see this

Not this

When

Delay  If the signal arrives its destination when it is supposed to.  Delay depends on the length of the transmission line and dielectric constant. In high speed digital system, the length of the transmission lines has the greatest impact of clock skew.

Clock skew: is the difference in the arrival time between two sequentially-adjacent registers

What  Parameters of PCB and components on it  The arrangement of components layout and high speed trace design  Reflection/crosstalk/power/ground noise  Electromagnetic Compatibility (EMC)  Electromagnetic Interference (EMI)

How

Solution: crosstalk, reflection  For crosstalk:  1. Reduce the coupling (a solid reference plane, both ground and power plane will do)  2. Change the timing  3. Improve receiver noise margins (as we stated before)  4. Downsize the aggressor nets (prevent large voltages from affecting small ones, not always the case with digital logic)  degree routing, avoid parallel layout (to minimize the impact)  6. More…

Solutions  For reflections:  Happens when impedance changes while the signal is transmitting.  L> Tr/2Tpd  Tpd: Transport Delay/unit length  Impedance matching:

Matching  1. Parallel: load impedance matching (close to load side) 2. Series: source impedance matching (close to source side, R + R s ≥ R L )

Summary

Reference  / /   analysis-for-high-speed-digital-pcb/ 

Thank you !