Monolithic Power Systems, Inc. · NASDAQ:MPWR
Monolithic Power Systems — Technical Presentation (April 2023)
25 slides from Monolithic Power Systems's technical presentation, April 2023
Slide 1: Replacing Optical Encoders with Magnetic Position Sensors
Replacing Optical Encoders with Magnetic Position Sensors April 2023 rev 20180504
Slide 2: Agenda
Agenda Types of Optical Encoders Comparison to Magnetic Position Sensors Typical Motor Applications Choosing a Magnetic Sensor Target Magnet Decisions Simulation for Magnetics/Mechanicals Q&A
Slide 3: Types of Optical Encoders
Types of Optical Encoders 8 tracks = 8 bits: requires 8 LED / receiver pairs Cost scales with resolution
Slide 4: Digi-Key Sampling of Optical Encoders
Digi-Key Sampling of Optical Encoders Digi-Key Price: $979 Digi-Key Price: $56 Digi-Key Price: $21 Digi-Key Price: $114
Slide 5: Comparison to Magnetic Position Sensors
Comparison to Magnetic Position Sensors Optical Magnetic Resolution (bits) 25+ 15 to 16 Accuracy (max INL) N/A 0.6 / <0.1 30x30 to 3x3/ Size (mm) 100x100 2x2 Cost $6 to $100+ $1 to 2 (sensor + magnet) Flexibility None Yes Output Incremental or Absolute Absolute Angle +
Slide 6: Operation Principles
inciples Operation Pr ee Peau 7/7 mrS
Slide 7: Typical Motor Applications
Typical Motor Applications mrS
Slide 8: Sensor Decision Tree
Sensor Decision Tree MA600 Need high resolution/ MA782 bandwidth? Need low MA3xx Series power? Need motor commutation MA8xx (U, V, W)? HMI only? MA7xx
Slide 9: Magnets
Magnets Materials/Geometries
Slide 10: Magnet Design Tradeoffs
Magnet Design Tradeoffs • Single Dipole (Diametral) • Easy to Simulate • True Absolute Position • Inexpensive • Only Option for On-Axis (Off-Axis Is Possible) • Multipole (Radial or Axial) • Double the Pole Pairs, Gain 1 Bit! • Side-Shaft (Off-Axis) Only • Airgap Must Be Tight for High PP Counts • C
Slide 11: Magnet Materials
Magnet Materials Working Temp Br (mT) Comments (°C) Neodymium • Very high resistance to demagnetization Sintered 1200 to 1400 80 to 150 • Susceptible to corrosion; needs coating Bonded 470 to 620 130 • Most common target magnet SmCo • High resistance to demagnetization Sintered 820 to 1050 250 to 30
Slide 12: Mechanical Considerations
Mechanical Considerations Attachment to Shaft: PCB/Sensor Placement: - Epoxy - On-Axis/End of Shaft - Press Fit - Off-Axis/Side-Shaft - Magnet Coupling - Off-Axis Orthogonal - Magnetic Assembly
Slide 13: Coordinate System Conventions
Coordinate System Conventions BZ Axial (Ignored) BX Tangential (BT) BY Radial (BR)
Slide 14: Tools
Tools Simulation/Lab Set-Up
Slide 15: Application Notes
Application Notes Appendix A: Sensor Position for a Cylinder without a Hole k | i H i i ai dy al i i Use Table 1a and Table 1b to determine the height and radius ofthe cylinder. 6 ‘Table ta: Specifications to Determine the Height of the Cylinder Dim) dolore) | 3 a 3 n z D 3 wm] 4 ol a1 [a6 [arf ass
Slide 16: MPS Online Simulation
MPS Online Simulation Simulates for all magnet and sensor topologies Finds optimum mechanical positioning for a particular magnet material and dimension Includes tolerance analysis effect on angle error http://sensors.monolithicpower.com/
Slide 17: Finite Element
Finite Element • Used for Simulation when… • There is a high-permeability material nearby • The target magnet has no symmetry • Why I Rarely Recommend FEM • Software is complex and expensive • Results are highly dependent on optimized mesh, proper boundary conditions, and problem definition • In the
Slide 18: Real Measurements
Real Measurements “The Universe is the best physics 3D Magnetic Field Scanning Set-Up simulator.” - One of my college professors
Slide 19: Sample Simulation
Sample Simulation Magnet Size - ID = 4mm - OD = 10mm - H = 3mm Sensor Placement - DAXIAL = -3mm - DRADIAL = +5mm Magnet Material - Sintered Neodymium
Slide 20: Off-Axis Sensing
Off-Axis Sensing Side-Shaft Position
Slide 21: Off-axis Compensation
Off-axis Compensation Angle (deg) mrS
Slide 22: Choosing a Magnetic Sensor
Choosing a Magnetic Sensor Part Resolution Number Description Output Format (bits) TMR – Newest, High-Accuracy 0.5° (0.1°) INL, High highest Bandwidth and Resolution, Digital Magnetic Angle ABZ, PWM, Reduced Wire Mode, resolution, MA600 Sensor Hall highest– Programmable bandwidth resolution / SPI, S
Slide 23: Sensor Selection Starting Point
Sensor Selection Starting Point Part Resolution Description Output Format Number (bits) ABZ, PWM, Reduced MA600 TMR – New, high resolution/bandwidth Wire Mode, SPI, SSI, 15 UVW MA732 Hall – Programmable resolution/bandwidth ABZ, PWM, SPI, SSI 14 Hall – Low power; consider for anything MA780 SPI 12 o
Slide 24: Reduce Cost with Magnetic Encoders
Reduce Cost with Magnetic Encoders Optical Encoder Magnetic Encoder Customer Benefits: Reduce Cost Reduce Size Operates in Harsh Environments without Costly Enclosures
Slide 25: Thank You
Thank You ted.smith@monolithicpower.com rev 20180504
Monolithic Power Systems — Technical Presentation (April 2023) on 6ix