Qualcomm Interview Questions


In building the timing constraints, do you need to constrain all IO (Input-Output) ports?
  • Can a single port have multi-clocked? How do you set delays for such ports?
  • How is scan DEF (Design Exchange Format) generated?
  • What is purpose of lockup latch in scan chain?
  • Explain short circuit current.
Answer: Short Circuit Power
  • What are pros/cons of using low Vt, high Vt cells?
Answer:
Multi Threshold Voltage Technique
Issues With Multi Height Cell Placement in Multi Vt Flow
  • How do you set inter clock uncertainty?

Answer:
set_clock_uncertainty –from clock1 -to clock2
  • In DC (Design Compiler), how do you constrain clocks, IO (Input-Output) ports, maxcap, max tran?
  • What are differences in clock constraints from pre CTS (Clock Tree Synthesis) to post CTS (Clock Tree Synthesis)?
Answer:

Difference in clock uncertainty values; Clocks are propagated in post CTS.
In post CTS clock latency constraint is modified to model clock jitter.
  • How is clock gating done?
Answer: Clock Gating
  • What constraints you add in CTS (Clock Tree Synthesis) for clock gates?

Answer:
Make the clock gating cells as through pins.
  • What is trade off between dynamic power (current) and leakage power (current)?
Answer:
Leakage Power Trends
Dynamic Power

  • How do you reduce standby (leakage) power?
Answer: Low Power Design Techniques
  • Explain top level pin placement flow? What are parameters to decide?
  • Given block level netlists, timing constraints, libraries, macro LEFs (Layout Exchange Format/Library Exchange Format), how will you start floor planning?
  • With net length of 1000um how will you compute RC values, using equations/tech file info?
  • What do noise reports represent?
  • What does glitch reports contain?
  • What are CTS (Clock Tree Synthesis) steps in IC compiler?
  • What do clock constraints file contain?
  • How to analyze clock tree reports?
  • What do IR drop Voltagestorm reports represent?
  • Where /when do you use DCAP (Decoupling Capacitor) cells?
  • What are various power reduction techniques?
Answer: Low Power Design Techniques

Source:
[http://vlsifaq.blogspot.com/]

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