ECE 453 Embedded Microprocessor System Design

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ECE 453Embedded MicroprocessorSystem Design
Week 8

• Michael G. Morrow, P.E.

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Topics

• Bus Signaling Technologies
• Interfacing to Inductive Loads
• Motor Interfacing
• Stepper Motors
• Power Transistors
• Heatsinking

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Bus Technologies and Standards

• The bus signaling technology determines the
  ultimate performance of the bus.
• Single-ended Technologies
• What does single-ended mean?
• Standards
• Incident-wave signaling
• Reflected-wave signaling
• Differential Technologies
• What does differential mean?
• Standards

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Technology Examples

• Gunning Transceiver Logic
• GTL
• Low-Voltage Differential-Signaling
• LVDS (TIA/EIA-644, RS-644)
• Point-to-point
• Multi-drop
• M-LVDS (TIA/EIA-899)
• Multipoint

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Interfacing to Inductive Loads

• Inductive Loads
• Motors
• Electromechanical Actuators
• Solenoids / Solenoid Valves
• Electromagnetic Relays
• Inductor Effects
• RL Transient Review
• Switching Inductive Loads
• Example

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Driving Inductive Loads

• DC Loads
• Drive Circuits
• BJTs versus MOSFETs
• Protection Circuits
• R
• C
• RC
• Diode
• MOSFET avalanche and active clamps
• AC Loads
• Drive Circuits

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DC Motors

• Applications
• Motor Characteristics
• Direction Control
• H-bridge
• Speed Control
• Torque is proportional to current
• Current is a function of supply voltage and motor
  rotational velocity
• Bottom line supply voltage does not control
  speed, unless torque is constant

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Stepper Motors

• Characteristics
• Applications
• Capability Measures
• Movement
• Stepper Motor Construction
• Variable Reluctance
• Permanent Magnet
• Hybrid

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Stepper Motor Operation

• VR Motor Operation
• PM Motor Operation
• Stepping Modes
• One phase on
• Two phase on
• Half-stepping
• Micro-stepping
• Winding construction
• Unipolar
• Bipolar
• Actual Construction
• Stepper Motor Controllers
• MC33192

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Power Transistors

• Packages
• TO-92
• TO-220 / TO-263
• TO-3
• SMT Packages
• Thermal Characteristics
• Mounting Methods
• Insulators

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Thermal Management

• Thermal Modeling
• We can model the thermal system as an electric
  circuit.
• Heatsink Applications
• Convection
• Forced-air
• Active cooling
• Heatsink Characteristics
• Exercises

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Wrapping Up

• Spring Break!
• Week 9
• PCI and Advanced Buses

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Heatsink Exercises

• Determine the maximum power that can be safely
  dissipated by an LM340-5 (in a TO-220 package) in
  still air at 68F.
• What will TJ be if operating from a 12V supply
  with 800mA supplied to the load. Assume TA 40C
  and you are using a Wakefield 634-15ABP heatsink
  in still air.

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Single-ended Bus Standards
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Differential Bus Standards
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Gunning Transceiver Logic

• GTL
• GTL

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LVDS

• Point-to-point
• Simplex

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LVDS

• Multi-drop
• Simplex

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M-LVDS

• Shared bus
• Half-duplex

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Actual Motor Construction
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Multi-pole Rotation, One-Coil On
A S B OFF
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Multi-pole Rotation
Multi-pole Rotation, One-Coil On
A OFF B S
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Multi-pole Rotation
Multi-pole Rotation, One-Coil On
A N B OFF
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Multi-pole Rotation
Multi-pole Rotation, One-Coil On
A OFF B N
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Multi-pole Rotation
Multi-pole Rotation, One-Coil On
A S B OFF
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DC Motor Characteristics

• Equivalent Circuit
• Current versus speed at constant VS
• Commutation
• Brushless DC Motors

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Inductive Load Drive Circuits

• BJTs
• VCEsat 0.4V
• PD ICVCE
• VCEsat kT-1
• MOSFETs
• VDS ID RDSon
• PD IDVDS ID2 RDSon
• RDSon kT

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Active Clamps (Protected FETs)
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Switching Characteristics
VC
VIN
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Switching Characteristics
VC
VIN
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AC Motor Drive Circuits
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H-bridge

• An H-bridge consists of two high-side switches
  (Q1,Q3) and two low-side switches (Q2,Q4)
• BJTs or FETs

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VR Stepper Motor
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One phase on Stepping
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Two phase on Stepping
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Half-stepping
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Unipolar motor
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Bipolar motor
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TO-92
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TO-3
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TO-220 / TO-263
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SMT Packages
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Thermal Characteristics
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MC33192
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MC33192