SLEWRATER - Slew Rate (Differential IO)

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Modified by Phil Loughhead on Sep 22, 2014

Model Kind

General

Model Sub-Kind

Generic Editor

SPICE Prefix

Model Name

SLEW

SPICE Netlist Template Format

@DESIGNATOR %%vd(%1,%2) %%vd(%3,%4) @"DESIGNATOR"SLEW .MODEL @"DESIGNATOR"SLEW slew (?rise_slope|rise_slope=@rise_slope| ?fall_slope|fall_slope=@fall_slope|)

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.

Rise_Slope	maximum rising slope value (Default = 1.0e9).
Fall_Slope	maximum falling slope value (Default = 1.0e9).

Notes

This model provides a simple slew rate feature that limits the absolute rising and falling slope of the output, with respect to time, to a defined value.

The values for the Rise_Slope and Fall_Slope parameters are specified in units of Vs^-1 or As^-1. For example, to enter a slew rate of 0.05V/us, the entry would be 0.5e7.

The function will raise or lower the output value until the difference between the input and output is zero. It will then follow the input until the rise or fall slope limits are again exceeded.

The input signal can be either a differential current or differential voltage signal.

Examples

Consider the slew rate function in the above image, with the following characteristics:

Pin1 (positive input) is connected to net In1
Pin2 (negative input) is connected to net GND
Pin3 (positive output) is connected to net Out
Pin4 (negative output) is connected to net GND
Designator is U2
Rise_Slope = 2e7
Fall_Slope = 2e7

The entry in the SPICE netlist would be:

*Schematic Netlist: AU2 %vd(IN1,0) %vd(OUT,0) AU2SLEW .MODEL AU2SLEW slew (rise_slope=2e7 fall_slope=2e7)

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 100.0u
Transient Step Time - set to 20.00n
Transient Max Step Time - set to 20.00n