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I am designing a D flip-flop. While doing my pre-layout simulations, I wasn't getting the output Q for the inputs, see attachments.

But when I tried to take the output from CLKPULSE, I was getting some zigzag signals.

Can you share your thoughts on this?

Using Cadence environment, TSMC 180nm Tech

Output Waveforms

Schematic Diagram

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  • \$\begingroup\$ Is there RTL associated with this? or, maybe, is this a structural sim... either way is this written in Verilog/VHDL? \$\endgroup\$
    – CapnJJ
    Jun 2, 2018 at 1:58
  • \$\begingroup\$ Verilog-A? I am out on this (but, I wish I knew more about Verilog-A) :/ Check/post on Mentor's verficationacademy.com \$\endgroup\$
    – CapnJJ
    Jun 2, 2018 at 3:30
  • \$\begingroup\$ All the D-FF's I have seen look rather different. Using two sets of "feed-back inverters" and transmission gates: allthingsvlsi.wordpress.coma/tag/… \$\endgroup\$
    – Oldfart
    Jun 2, 2018 at 7:47

1 Answer 1

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  1. @CapnJJ I believe it is custom design with 0.18um.
  2. @Vinay: First of all you need to run realistic simulations. Find ft of your technology. Now find 0.2ft. Set the rise and fall time accordingly for input signals. A realistic input signal is shown in 3 below.
  3. A Non-overlapping two-phase clock generator with adjustable duty cycle
  4. DETFF, The Usage of Dual Edge Triggered Flip-flops in Low Power, Low Voltage Applications
  5. More helpful, Low power dual edge - Triggered static D flip-flop
  6. All the sizes in your schematics are pw, nw and rw. I think you can read up more about analog design before attempting tape out.
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