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Liberate Characterization Error (removal_rising/fall) for Sequential Cells

Hi All,

When characterizing a custom made D-flip flop at nominal conditions (1.2V/25C), Liberate runs into following error :

ERROR (LIB-52): The constraint search failed to find a solution within the search range for arc of cell:'UTDFRQ1RVT', r_pin:'CK', r_pin dir:'r', pin:'RB', pin dir:'r', type:'removal_rising rise_constraint' when: D, GLITCH_PROBE. This cell will be marked as failed and the constraint data will be set to: 1.0 (see constraint_failed_value). To debug, review the saved simulation results for deck: removal_27. Possible causes include: 'constraint_glitch_peak' too small; 'constraint_check_final_state_threshold' too large; estimated search range too small (see constraint_search_bound). Modify the constraint parameters and rerun.

ERROR (LIB-52): The constraint search failed to find a solution within the search range for arc of cell:'UTDFRQ1RVT', r_pin:'CK', r_pin dir:'f', pin:'RB', pin dir:'r', type:'removal_falling rise_constraint' when: D, GLITCH_PROBE. This cell will be marked as failed and the constraint data will be set to: 1.0 (see constraint_failed_value). To debug, review the saved simulation results for deck: removal_29. Possible causes include: 'constraint_glitch_peak' too small; 'constraint_check_final_state_threshold' too large; estimated search range too small (see constraint_search_bound). Modify the constraint parameters and rerun.

Although the mentioned constraint parameters were slightly adjusted (constraint_glitch_peak = 0.5, constraint_check_final_state_threshold = 0.3 to 0.7, constraint_search_bound = 1e-9), the issue seems to persist. Could this be due to a bug in the Liberate version ? Current version we have is LIBERATE_16.14.122.

Thanks in advance

Anuradha

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