NAME_TABLE:

C_Function_Name: cm_ilimit

Spice_Model_Name: ilimit

Description: "current limiter block"

PORT_TABLE:

Port Name: in pos_pwr

Description: "input" "positive power supply"

Direction: in inout

Default_Type: v g

Allowed_Types: [v,vd] [g,gd]

Vector: no no

Vector_Bounds: - -

Null_Allowed: no yes

PORT_TABLE:

Port Name: neg_pwr out

Description: "negative power supply" "output"

Direction: inout inout

Default_Type: g g

Allowed_Types: [g,gd] [g,gd]

Vector: no no

Vector_Bounds: - -

Null_Allowed: yes no

PARAMETER_TABLE:

Parameter_Name: in_offset gain

Description: "input offset" "gain"

Data_Type: real real

Default_Value: 0.0 1.0

Limits: - -

Vector: no no

Vector_Bounds: - -

Null_Allowed: yes yes

PARAMETER_TABLE:

Parameter_Name: r_out_source r_out_sink

Description: "sourcing resistance" "sinking resistance"

Data_Type: real real

Default_Value: 1.0 1.0

Limits: [1.0e-9 1.0e9] [1.0e-9 1.0e9]

Vector: no no

Vector_Bounds: - -

Null_Allowed: yes yes

PARAMETER_TABLE:

Parameter_Name: i_limit_source

Description: "current sourcing limit"

Data_Type: real

Default_Value: -

Limits: [1.0e-12 -]

Vector: no

Vector_Bounds: -

Null_Allowed: yes

PARAMETER_TABLE:

Parameter_Name: i_limit_sink

Description: "current sinking limit"

Data_Type: real

Default_Value: -

Limits: [1.0e-12 -]

Vector: no

Vector_Bounds: -

Null_Allowed: yes

PARAMETER_TABLE:

Parameter_Name: v_pwr_range i_source_range

Description: "upper & lower power "sourcing current

supply smoothing range" smoothing range"

Data_Type: real real

Default_Value: 1.0e-6 1.0e-9

Limits: [1.0e-15 -] [1.0e-15 -]

Vector: no no

Vector_Bounds: - -

Null_Allowed: yes yes

PARAMETER_TABLE:

Parameter_Name: i_sink_range

Description: "sinking current smoothing range"

Data_Type: real

Default_Value: 1.0e-9

Limits: [1.0e-15 -]

Vector: no

Vector_Bounds: -

Null_Allowed: yes

PARAMETER_TABLE:

Parameter_Name: r_out_domain

Description: "internal/external voltage delta smoothing range"

Data_Type: real

Default_Value: 1.0e-9

Limits: [1.0e-15 -]

Vector: no

Vector_Bounds: -

Null_Allowed: yes

• Description:
  The Current Limiter models the behavior of an operational amplifier or comparator device at a high level of abstraction. All of its pins act as inputs; three of the four also act as outputs. The model takes as input a voltage value from the in connector. It then applies an offset and a gain, and derives from it an equivalent internal voltage (veq), which it limits to fall between pos_pwr and neg_pwr. If veq is greater than the output voltage seen on the out connector, a sourcing current will flow from the output pin. Conversely, if the voltage is less than vout, a sinking current will flow into the output pin.
  Depending on the polarity of the current flow, either a sourcing or a sinking resistance value (r_out_source, r_out_sink) is applied to govern the vout/i_out relationship. The chosen resistance will continue to control the output current until it reaches a maximum value specified by either i_limit_source or i_limit_sink. The latter mimics the current limiting behavior of many operational amplifier output stages.
  During all operation, the output current is reflected either in the pos_pwr connector current or the neg_pwr current, depending on the polarity of i_out. Thus, realistic power consumption as seen in the supply rails is included in the model.
  The user-specified smoothing parameters relate to model operation as follows: v_pwr_range controls the voltage below vpos_pwr and above vneg_pwr inputs beyond which (veq = gain\left( {vin + v_{offset}} \right)) is smoothed; i_source_range specifies the current below i_limit_source at which smoothing begins, as well as specifying the current increment above i_out=0.0 at which i_pos_pwr begins to transition to zero; i_sink_range serves the same purpose with respect to i_limit_sink and i_neg_pwr that i_source_range serves for i_limit_source and i_pos_pwr; r_out_domain specifies the incremental value above and below (veq-vout)=0.0 at which r_out will be set to r_out_source and r_out_sink, respectively. For values of (veq-vout) less than r_out_domain and greater than -r_out_domain, r_out is interpolated smoothly between r_out_source and r_out_sink.

Example SPICE Usage:

a10 3 10 20 4 amp3

.

.

.model amp3 ilimit(in_offset=0.0 gain=16.0 r_out_source=1.0

+ r_out_sink=1.0 i_limit_source=1e-3

+ i_limit_sink=10e-3 v_pwr_range=0.2

+ i_source_range=1e-6 i_sink_range=1e-6

+ r_out_domain=1e-6)