555 Timer as Astable Multivibrator (Oscillator) model error PUBLIC

UPDATE: For a while, around 130723, the CL 555 timer model appeared to now operate correctly but as at 131202, it is broken again as described below.

The high level voltage at the OUTPUT pin of the CL 555
timer model does not track the vcc supply. It is fixed at 5V.

The CL model uses a fixed internal supply of 5V and
ignores the voltage on the vcc pin. This means that the
internal switching thresholds are fixed at 5/3V and 10/3V.

This is incorrect and can be misleading.

Simulate > Time Domain > Run Time-Domain Simulation

The high level voltage at the OUTPUT pin of the CL 555 timer model does not track the vcc supply. It is fixed at 5V.

The CL model uses a fixed internal supply of 5V and ignores the voltage on the vcc pin. This means that the internal switching thresholds are fixed at 5/3V and 10/3V.

This is incorrect and can be misleading.

The circuit below correctly models the output swing of the real 555 timer although it does not accurately model the output stage behaviour vs. load currents.

Simulate > Time Domain > Run Time-Domain Simulation