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 1mΩ. If you require a resistance of less than 1mΩ, 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.

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 Library:	SIMPLIS_DIGI1.LB
Subcircuit Name:	SIMPLIS_DIGI1_COMP_Y
Symbol:
Multiple Selections:	Only one device at a time can be edited.

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 any input pin changes state until the outputs change state
Hysteresis		The Hysteresis (H) of the comparator. To determine the actual threshold (TL, TH), substitute Hysteresis (HYSTWD) 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 Comparator 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 high voltage for each Comparator output pin
Initial Condition	Initial condition of the Comparator output at time=0

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
DELAY	Propagation Delay	Number	1f to 1024	s	Delay from when any input pin changes state until the outputs change state
GNDREF	Ground Ref	String	'Y' 'N'	none	Determines whether or not a device has a ground reference pin. Any digital component that has an input or output pin connected to an analog circuit node must have its Ground Ref pin connected to an analog node. This is usually the ground on the schematic.
HYSTWD, TH	Hysteresis, Threshold	Number	min: 1f	V		Hysteresis and Threshold of the inputs. The hysteretic-window width, HYSTWD is centered around Threshold (TH) voltage. To determine the actual threshold ( TL , THI ), substitute Threshold (TH) and Hysteresis (HYSTWD) in each of the following formulas: Input Logic Level Actual Threshold 1 Threshold + 0.5 * Hysteresis 0 Threshold - 0.5 * Hysteresis
IC	Initial Condition	Number	0 1	none	Initial condition of the Inverter/Buffer output at time=0
RIN	Input Resistance	Number	min: 100	Ω	Input resistance of each Inverter/Buffer input pin
ROUT	Output Resistance	Number	min: 1m	Ω	Output resistance of each Inverter/Buffer output pin
VOH	Output High Voltage	Number	any	V	Output high voltage for each Inverter/Buffer output pin
VOL	Output Low Voltage	Number	any	V	Output high voltage for each Inverter/Buffer output pin