DIVIDER - Divider (Differential IO)

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Model Kind

General

Model Sub-Kind

Generic Editor

SPICE Prefix

A

Model Name

DIVIDE

SPICE Netlist Template Format

@DESIGNATOR %%vd(%1,%2) %%vd(%3,%4) %%vd(%5,%6) @"DESIGNATOR"DIVIDE
.MODEL @"DESIGNATOR"DIVIDE divide (?num_offset|num_offset=@num_offset| ?num_gain|num_gain=@num_gain| ?den_offset|den_offset=@den_offset| ?den_gain|den_gain=@den_gain| ?den_lower_limit|den_lower_limit=@den_lower_limit| ?den_domain|den_domain=@den_domain| ?fraction|fraction=@fraction| ?out_gain|out_gain=@out_gain| ?out_offset|out_offset=@out_offset|)

Parameters (definable at component level)

The following component-level parameters are definable for this model type and are listed on the Parameters tab of the Sim Model dialog. To access this dialog, simply double-click on the entry for the simulation model link in the Models region of the Component Properties dialog.

Num_Offset

numerator offset (Default = 0).

Num_Gain

numerator gain (Default = 1).

Den_Offset

denominator offset (Default = 0).

Den_Gain

denominator gain (Default = 1).

Den_Lower_Limit

denominator lower limit (Default = 1.0e-10).

Den_Domain

denominator smoothing domain (Default = 1.0e-10).

Fraction

used to control whether the smoothing domain is specified as a fractional (TRUE) or absolute (FALSE) value. (Default = FALSE).

Out_Gain

output gain (Default = 1).

Out_Offset

output offset (Default = 0).

Notes

This is a two-quadrant divider. It takes two inputs (one specified as the numerator, the other as the denominator) and processes them to obtain the output result as follows:

  • The inputs are offset, in accordance with the values specified for the Num_Offset and Den_Offset parameters.
  • The offset signals are then multiplied by the values for gain specified in the respective Num_Gain and Den_Gain parameters.
  • The resulting values are divided
  • The quotient is multiplied by the value specified for the Out_Gain parameter.
  • The output result is then offset in accordance with the value specified for the Out_Offset parameter.

The process can be expressed mathematically as follows:

Output = ((((Num + Num_Offset) * Num_Gain) / ((Den + Den_Offset) * Den_Gain)) * Out_Gain) + Out_Offset

The denominator is prevented from ever going zero by specification of a limiting positive value in the Den_Lower_Limit parameter. This limit is reached through the use of a quadratic smoothing function, the domain of which is specified using the Den_Domain parameter.

This model will operate in DC, AC and Transient analysis modes only. When running an AC Small Signal analysis, the results are only valid when one of the two inputs, not both, is connected to an AC signal.

The input signals can be either differential current or differential voltage signals.

Examples

Consider the divider in the above image, with the following characteristics:

  • Pin1 (positive num input) is connected to net In1
  • Pin2 (negative num input) is connected to net In2
  • Pin3 (positive den input) is connected to net In3
  • Pin4 (negative den input) is connected to net In4
  • Pin5 (positive output) is connected to net Out
  • Pin6 (negative output) is connected to net GND
  • Designator is U1
  • Out_Gain = 4
  • All other model parameters are left at their inherent default values

The entry in the SPICE netlist would be:

*Schematic Netlist:
AU1 %vd(IN1,IN2) %vd(IN3,IN4) %vd(OUT,0) AU1DIVIDE
.MODEL AU1DIVIDE divide (out_gain=4)

The effect of the function can be seen in the resultant waveforms obtained by running a transient analysis of the circuit. 

In this example, the following analysis parameters on the Transient/Fourier Analysis page of the Analyses Setup dialog have been used:

  • Transient Start Time - set to 0.000
  • Transient Stop Time - set to 50.00m
  • Transient Step Time - set to 200.0u
  • Transient Max Step Time - set to 200.0u
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