SIMPLIS Parts

Comparator with Analog Inputs and Digital Outputs

The Comparator with Analog Inputs and Digital Outputs models a generic comparator with hysteresis. The output of the comparator is treated as a digital signal for the SIMPLIS event-driven simulator only if the output is connected to SIMPLIS digital devices. If the comparator output is connected to analog devices, the output voltage levels and output resistance are defined by the Output High Voltage, Output Low Voltage, and the Output Resistance parameters.

There is a finite resistance from each comparator input to the comparator ground pin. If you have an application where you require the comparator to have a true infinite input impedance, you can use a voltage-controlled voltage source (VCVS) to buffer each input pin. Similarly, the outputs of the comparator have a finite output resistance with a minimum value of 1m&#x2126. If you require a resistance of less than 1m&#x2126, you can add a VCVS to the output of the comparator. The circuit example below demonstrates this technique.

The Hysteresis parameter may never be zero. The minimum parameter value allowed is 1pV. For most applications, this is sufficiently small to be insignificant.

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Model Name:

Comparator with Analog Inputs and Digital Outputs

Simulator:

This device is compatible with the SIMPLIS simulator.

Parts Selector
Menu Location:

Digital Functions | Gates

Symbol Library:

None - the symbol is automatically generated when placed or edited.

Model File:

SIMPLIS_DIGI1.lb

Subcircuit Name:

SIMPLIS_DIGI1_COMP_Y

Symbol:

Multiple Selections:

Multiple comparators can be selected and edited at the same time.

Editing the Comparator with Analog Inputs and Digital Outputs

To configure the comparator with analog inputs and digital outputs, follow these steps:

  1. Double click the symbol on the schematic to open the editing dialog to the Parameters tab.
  2. Make the appropriate changes to the fields described in the table below the image.
Label Parameter Description

Propagation Delay

Delay from when an input pin goes active until the output changes

Hysteresis

The Hysteresis (H) of the comparator. To determine the low-to-high threshold (TH) and the high-to-low threshold (TL), substitute Hysteresis (H) in each of the following formulas, where INN is the negative input pin voltage. The comparator output voltage will change state when INP, the positive input pin voltage, reaches TL or TH :
Output Logic Transition Actual Threshold
0 ➞ 1 TH = INN + 0.5 * Hysteresis
1 ➞ 0 TL = INN - 0.5 * Hysteresis
 

Input Resistance

Input resistance of each input pin

Output Resistance

Output resistance of each comparator output pin

Output High Voltage

Output high voltage for each comparator output pin

Output Low Voltage

Output low voltage for each comparator output pin

Initial Condition

Initial condition of the comparator's non-inverted output at time=0

Examples

The test circuit used to generate the waveform examples in the next section can be downloaded here: simplis_018_comparator_example.sxsch.

Waveforms

The waveforms below were taken from a comparator with a 1V Hysteresis parameter, and a slow triangle wave ramp applied to the input. The comparator output switches from low to high when the ramp reaches 3V and from high to low when the ramp reaches 2V.


Subcircuit Parameters

The subcircuit parameters, parameter names, data types, ranges, units, and descriptions are in the following table. The parameter names can be used to directly generate netlist entries for the device. For example, the netlist entry for a comparator with analog inputs and digital outputs would be as follows:
X$U1 7 9 0 6 8 SIMPLIS_DIGI1_COMP_Y vars: IC=0 RIN=10Meg ROUT=10 HYSTWD=1 VOL=0 VOH=5 DELAY=2p


Parameter Name Label Data Type Range Units Parameter Description

HYSTWD

Hysteresis

    

V

The Hysteresis (H) of the comparator. To determine the low-to-high threshold (TH) and the high-to-low threshold (TL), substitute Hysteresis (H) in each of the following formulas, where INN is the negative input pin voltage. The comparator output voltage will change state when INP, the positive input pin voltage, reaches TL or TH :

Output Logic Transition Actual Threshold
0 ➞ 1 TH = INN + 0.5 * Hysteresis
1 ➞ 0 TL = INN - 0.5 * Hysteresis
 

IC

Initial Condition

LIST

0,
1

  

Initial condition of the comparator's non-inverted output at time=0

RIN

Input Resistance

  

min: 100

Ω

Input resistance of each input pin

VOH

Output High Voltage

    

V

Output high voltage for each comparator output pin

VOL

Output Low Voltage

    

V

Output low voltage for each comparator output pin

ROUT

Output Resistance

  

min: 1m

Ω

Output resistance of each comparator output pin

DELAY

Propagation Delay

  

1f to 1024

s

Delay from when an input pin goes active until the output changes

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