MCHP Comparator / Op-Amp / Voltage Reference

dsPIC30F 30F series dsPIC33F 33FJ series

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Legacy comparator, op-amp, and voltage reference configuration for dsPIC30F and dsPIC33FJ devices

When to use:

When to use:

• Legacy dsPIC30F or dsPIC33FJ target device (DS70357 & DS70648 datasheets)
• Older project maintenance or existing design migration
• Internal CVR voltage reference needed (16-level programmable reference)
• Op-amp functionality available on device (unity gain, non-inverting, inverting)
• Comparator with digital filtering or blanking logic required

When NOT to use:

• Newer dsPIC33E/C/A device — use High-Speed Analog Comparator block instead
• Sub-microsecond response time needed — legacy comparator slower than HS version
• Slope compensation required — use High-Speed Analog Comparator w/ Slope block
• PGA functionality needed — use dedicated PGA block (dsPIC33C/A)

Overview

The MCHP Comparator / Op-Amp / Voltage Reference block provides access to the analog comparator, operational amplifier, and voltage reference (CVR) modules found in legacy dsPIC30F and dsPIC33FJ devices (DS70357 & DS70648). This block combines configuration for all three analog functions in a single interface.

Key Features:

• Multiple comparator instances (device-dependent)
• Comparator voltage reference (CVR) module
• Op-amp functionality (device-dependent)
• Configurable interrupt and event generation
• Digital filtering and blanking support
• Pin mapping for analog inputs and outputs

Typical Applications

• Signal Conditioning: Op-amp gain stages for sensor interfaces
• Threshold Detection: Comparator-based limit detection
• Reference Generation: CVR module for DAC functionality
• Motor Control: Current and voltage sensing
• Power Management: Supply voltage monitoring

Block Dialog

The Comparator / Op-Amps / Voltage Reference block opens its custom configuration window (not the Simulink mask) when double-clicked:

The window groups settings by physical peripheral:

• Voltage Reference 1 — internal resistance-network DAC; choose the AVdd / AVss or Vref+ / Vref- power rail, enter the analog rail voltages, and optionally route the reference to the CVref1O pin.
• Interrupt Priority — shared ISR priority for all comparators on the page.
• Comparator 1 / 2 / 3 (and more on chips with additional analog comparators) — one pane per comparator. Each pane’s drop-down is disabled by default; enabling it exposes the comparator’s input-muxing, hysteresis, filtering and output-polarity parameters.
• Sample Time — block sample time for any block-level output (status pins, interrupt-triggered subsystem call). -1 by default.

Parameters

Function Tab

Comparator/Op-Amp Configuration

Each comparator/op-amp instance can be independently configured:

CVR Module Configuration

Pins Configuration Tab

Input/Output Pin Mapping

Event and Interrupt Configuration

Advanced Filtering

Block Outputs

Note: Output ports are dynamically created based on BlockOutputEvent and BlockOutputState settings.

Notes

Legacy Device Support

This block is designed for legacy dsPIC30F and dsPIC33FJ devices. For newer devices:

• dsPIC33E/EP/EV: Use “High-Speed Analog Comparator” block
• dsPIC33C/CK/CH: Use “High-Speed Analog Comparator” block
• dsPIC33A: Use “High-Speed Analog Comparator” and “Op-Amp” blocks

Pin Availability

Available pins vary significantly by device package and configuration. The MCHP Master block detects available pins based on:

• Selected device
• Enabled peripherals
• Pin remapping (PPS) configuration

CVR Voltage Calculation

CVR output voltage depends on:

• CVRSS range selection
• RLadder tap selection
• Supply voltage (AVdd, AVss)

Formula:

• Low range: VCVR = (RLadder/24) × AVdd
• High range: VCVR = (AVdd/4) + (RLadder/32) × (3AVdd/4)

Filter and Blanking

Digital filtering and blanking features provide noise immunity:

• FilterFreq: Sets low-pass filter cutoff
• Blanking: Masks comparator output during specified conditions
• BlankingTruthTable: Defines complex blanking logic

Device Support

dsPIC30F Series

• Comparator modules: 1-5 (device-dependent)
• CVR module with 16 voltage levels
• Op-amp functionality (select devices)

dsPIC33FJ Series

• Comparator modules: 1-5 (device-dependent)
• CVR module with programmable output
• Enhanced filtering and blanking

Note: Newer dsPIC33E/C/A devices use separate dedicated blocks:

• Use High-Speed Analog Comparator block for dsPIC33E/C/A
• Use Op-Amp block for dsPIC33C/A devices
• Use PGA block for programmable gain amplifiers

Examples

Basic Comparator with Internal Reference

1. Set CON = "Comparator" for desired instance
2. Configure CREF (positive input) to internal CVR
3. Set RLadder to desired voltage level
4. Configure CCH (negative input) to external pin
5. Enable OutputPort_COE_RP for digital output

Op-Amp Configuration

1. Set CON = "Op-Amp" for desired instance
2. Select OPMODE (Unity Gain, Non-Inverting, etc.)
3. Map input pins appropriately
4. Verify device supports selected op-amp mode

CVR Module as DAC

1. Enable CVR1OE or CVR2OE
2. Set VREFSEL and CVRSS for range
3. Program RLadder for desired voltage
4. Output appears on CVR output pin

References

• dsPIC30F Family Reference Manual - Comparator Module
• dsPIC33F Family Reference Manual - Comparator with CVR
• Application Note AN1137: Analog Comparator Applications

Related Blocks

• High-Speed Analog Comparator: For dsPIC33E/C/A devices
• High-Speed Analog Comparator with Slope: Enhanced slope compensation
• Op-Amp: Dedicated op-amp block for dsPIC33C/A
• PGA: Programmable Gain Amplifier for dsPIC33A
• ADC: Analog-to-Digital Converter blocks