Transient Simulation of AMS gives convergence error

Hi,

I need to run a AMS simulation for a testbench that contains VerilogA block,  functional block (Verilog) and Transistor level schematics. From the Figure below you can have a look:

Here, The Input block is modelled in VerilogA, both CTRL and COI are in VerilogD and DelSig is in transistor level. Those views are selected in Config view for AMS simulation. When the AMS simulation is run, it gives an error that says -  ERROR (SPECTRE-16192): No convergence achieved with the minimum time step specified. Last acceptable solution computed at 1.00049 ns.

Can anybody please provide me a solution to solve this error? I am logged and cannot proceed further.

Thanks,

Ashraful