# Analog-Digital Schmitt Trigger

In this topic:

## Netlist entry

Axxxx in out model_name

## Connection details

 Name Description Flow Type Allowed types in Input inout g g, gd out Output out d d

## Model format

.MODEL model_name adc_schmitt parameters

## Model parameters

 Name Description Type Default Limits in_low Maximum 0-valued analog input real 0.1 none in_high Minimum 1-valued analog input real 0.9 none rise_delay Rise delay real 1nS $1\text{e}^{-12} - \infty$ fall_delay Fall delay real 1nS $1\text{e}^{-12} - \infty$ time_tol Threshold time tolerance real 100pS $1\text{e}^{-12} - \infty$ out_low Analog out for 'ZERO' input real 0 none out_high Analog output 'ONE' input real 5 none clamp_res Clamp minimum resistance real 1 1e-06 $- \infty$ clamp_bias Clamp voltage real 0.8 0.2 - 2 out_family Output logic family string UNIV none init_cond Initial condition real 0 none

## Device Operation

This device is basically identical to the Analog-Digital Interface Bridge. The only difference is the behaviour of the device when the analog input lies between the threshold voltages. With the interface bridge, the output is UNKNOWN under these circumstances but with this Schmitt Trigger, the output retains its previous value and so is always in a known state. In summary, the output will only switch from low to high when the input exceeds the higher threshold (IN_HIGH) and will only switch from high to low when the input descends below the lower threshold (IN_LOW).

If initial input voltage lies between the hysteresis thresholds, the output state is determined by the init_cond parameter.