NAME_TABLE:

C_Function_Name: cm_square

Spice_Model_Name: square

Description: "controlled square wave oscillator"

PORT_TABLE:

Port Name: cntl_in out

Description: "control input" "output"

Direction: in out

Default_Type: v v

Allowed_Types: [v,vd,i,id] [v,vd,i,id]

Vector: no no

Vector_Bounds: - -

Null_Allowed: no no

PARAMETER_TABLE:

Parameter_Name: cntl_array freq_array

Description: "control array" "frequency array"

Data_Type: real real

Default_Value: 0.0 1.0e3

Limits: - [0 -]

Vector: yes yes

Vector_Bounds: [2 -] cntl_array

Null_Allowed: no no

PARAMETER_TABLE:

Parameter_Name: out_low out_high

Description: "output peak low value" "output peak high value"

Data_Type: real real

Default_Value: -1.0 1.0

Limits: - -

Vector: no no

Vector_Bounds: - -

Null_Allowed: yes yes

PARAMETER.TABLE:

Parameter_Name: duty_cycle rise_time

Description: "duty cycle" "output rise time"

Data_Type: real real

Default_Value: 0.5 1.0e-9

Limits: [1e-6 0.999999] -

Vector: no

Vector_Bounds: - -

Null_Allowed: yes yes

PARAMETER_TABLE:

Parameter_Name: fall_time

Description: "output fall time"

Data_Type: real

Default_Value: 1.0e-9

Limits: -

Vector: no

Vector_Bounds: -

Null_Allowed: yes

• Description:
  This function is a controlled square wave oscillator with parametrizable values of low and high peak output, duty cycle, rise time, and fall time. It takes an input voltage or current value. This value is used as the independent variable in the piecewise linear curve described by the coordinate points of the cntl_array and freq_array pairs. From the curve, a frequency value is determined, and the oscillator will output a square wave at that frequency.
  From the above, it is easy to see that array sizes of 2 for both the cntl_array and the freq_array will yield a linear variation of the frequency with respect to the control input. Any sizes greater than 2 will yield a piecewise linear transfer characteristic. For more detail, refer to the description of the piecewise linear controlled source, which uses a similar method to derive an output value given a control input.

Example SPICE Usage:

ain 1 2 pulse1

.model pulse1 square(cntl_array = [-1 0 5 6]

+ freq_array=[10 10 1000 1000] out_low = 0.0

+ out_high = 4.5 duty_cycle = 0.2

+ rise_time = 1e-6 fall_time = 2e-6)