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TRANSCRIPT
Isolation Basics &
Isolation Applications
September 2008
2
Agenda
♦ Isolation requirements
� What is isolation?
� Why is isolation required?
� What are the safety and regulatory standards?
♦ Isolation applications
3
What is isolation?
♦ Galvanic isolation�No current flow from one circuit to another
�Signal information passes from one circuit to another
4
Why Do Systems Need Isolation?…
Non-Isolated System
HV Path
♦ A high-voltage breakdown path exists through the control circuitry
Hig
h V
olt
ag
e
5
Isolation Prevents Electrocution
♦ High voltage path is blocked because of high impedance between grounds
ISOLATOR
Very high impedance between grounds!
Hig
h V
olt
ag
e
6
Ground loop Common mode noise
Voltage transients Incompatible voltage levels
Isolation Resolves Design Problems
`
MCU or DSP
Bus Controller &
Transceiver
SIGNAL
RETURN
(-) (+)
Ground Loop
Ground Potential
Difference
Host
Computer
7
Regulatory Standards Organizations
German StandardsDKE (Deutscher Elektrotechnische Kommission)
Canadian StandardsCSA (Canadian Standards Associations)
International Electronic StandardsIEC (International Electrotechnical Commission)
U.S. StandardsUL (Underwriters Laboratories, Inc.)
Harmonizing of European StandardsCENELEC (European Committee for Electrotechnical
Standardization)
CharterOrganization Name
♦ Isolation compliance is regulated by governing Organizations
8
Application Vs. Global/Regional Safety Standards
804225145960950
41003950Telecom
0410 04111010126261010-11010-1
Measurement
and Control
8608730-16006565Household
7506012601-160601601Medical
60950950195060950950
Information
Technology
Equipment
16014-M9150850178204
604Industrial
DIN/VDECSA **UL*CENELEC
(EN)IECOrganization
GermanyCanadaU.S.EuropeInternationalApplication
♦ Different Countries regulate compliance via country’s
system standard
9
Optoisolator Component Level Specifications
DIN EN 60747-5-2
Component
Acceptance Notice #51577EN 60747-5-2IEC 60747-5-2Optoisolator
DIN/VDECSAULCENELECIECOrganization
GermanyCanadaU.S.EuropeInternational
♦ Component level certification regulated by component standard
♦ Certified components used to speed system level approval to country
standard (IEC60950, IEC61010, etc.)
10
Key Terms in Isolation
♦ Propagation Delay � The time it takes a signal a transition across the
barrier.
♦ Creepage� The distance along the insulating surface an arc
may travel.
♦ Clearance� The shortest path through air that an arc may
travel.
♦ Hazardous or Live� Voltage greater than 30 VRMS (42.4 VPEAK) or 60
VDC.
♦ SELV (safety extra-low-voltage)� Voltage less than 30 VRMS (42.4 VPEAK) or 60 VDC.
♦ Rated Voltage� The allowable continuous operating voltage that
the manufacturer specifies.
♦ Working Voltage� The highest possible root-mean square value of
the ac and dc voltage across insulation when the product is operating at it rated voltage.
♦ Isolation Voltage� Isolation voltage is based on qualification test
voltages that stresses the insulation of the product. High-pot (dielectric withstand) test are performed to determine isolation level for an isolation product.
Creepage
Clearance
Si8xxx
Si8xxx
11
Key Terms in Isolation (cont.)
♦ Functional Insulation
� Also called operational insulation, does not protect
or isolate against electrical shock, but is required
for a product to function.
♦ Basic insulation
� A single level of insulation that provides basic
protection against shock.
♦ Supplementary Insulation
� An independent insulation that manufacturers
apply in addition to basic insulation to reduce the
risk of electrical shock in the event of a failure of
basic insulation.
♦ Double Insulation
� Comprises both basic and supplementary
insulation.
♦ Reinforced insulation
� Is a single insulation system that provides
electrical-shock protection equivalent to double
insulation.
Note: Double, reinforced, and basic insulation are the most
important for safety isolation. For example, double insulation is required from SELV to hazardous live.
2.5KV isolator coverage at 120VAC
B – Basic Insulation
R – Reinforced Insulation
S – Supplementary Insulation
D – Double Insulation
Exert from IEC 60950
12
Isolator Key Specifications
♦ Isolation voltage� Maximum voltage across isolator
♦ Data rate/prop delay across isolator� Impacts loop stability & response in
control applications
ISOLATOR
OUTIN
GND1 GND2
∆V(max)
♦ Supply current� Impacts system power efficiency
♦ Common mode rejection� Error-free output when common
mode voltage is across isolator
13
Isolation Markets and Applications
Industrial
Automotive
Medical
Computer & Office Equipment
Communications
Consumer
•Automated test equipment
•Fieldbus
•Industrial communications
•Industrial networking
•Motor control
•PLC input/output isolation
•Power distribution systems
•Power generation
•Robotics
•Switching panel
•Switching power supplies
•Test & measurement
•Hybrid electric vehicles
•CANBus communications
•IPM motor inverter drives
•IPM DC-DC converters
•Inverters for battery chargers
•Battery/inverter voltage monitoring
•Defibrillators
•ECG/EKG
•Endoscopes
•Magnetic resonance imaging
•Patient monitoring
•Isolated input/output module
•Isolated USB hub
•Printers and plotters
•Automated meter reading
•Digital cross connect
•Distributed power architecture
•PBX and central office
•Power over ethernet
•Telephone switching equipment
•Telephone terminal equipment
•Wireless basestation
•Air conditioning
•Alarm systems
•Audio & video equipment
•Electronic gaming
•Fitness equipment
•Induction coolers
•Plasma displays
•Washing machines
14
Isolator Applications
Isolators
Si3226 ProSLIC
DSL/ProcessorDigital Isolators
Si3456Si3456
Opto
High VLow V
Control/ Monitor
DSL Gateway Ethernet Switch PoE
AutomotiveIndustrial/instrumentation/medical
+X
15
♦ Digitize sensor output from ADC in harsh environment
♦ Isolate high-speed digital signals from noise-sensitive analog circuits
Serial Output ADC
Parallel Output ADC
Isolated Data Acquisition
16
Industrial (Serial Field Bus) Communication
♦ Central communication to distributed field devices
� PROFIBUS - twisted pair serial (like RS485): 1.5Mbps or 12Mbps
� DeviceNet, others…
♦ Application requirements: <25Mbps, low prop delay, reliability
17
Industrial Communications - Isolated RS232/422, USB
♦ Isolation prevents common mode transients from corrupting data in a noisy environment
MCU/DSP
ISOLATION
ISOLATOR
ISOLATOR
D+
D-
USB I/O
RS232/422 USB
18
Industrial PLC I/O
♦ Isolates the low-voltage processor logic from drive voltages
Programmable Logic Controller I/O Unit
Logic
circuit
19
Automotive Isolation
♦ Hybrid electric cars, intelligent power module (IPM), digital signal isolation
♦ CANBus comm., power transistor isolation, MCU/ADC/DAC digital isolation
♦ Application requirements: wide temp range (-40 to 125C), high reliability
M
Isolation
MCU
or
DSP
CAN
Transceiver
MCU
Other
Devices
Isolation
UART
Network Controller
Bus Interface
Intelligent Power Module Automotive CANBus
20
Power Over Ethernet (PSE)
♦ Isolate I2C signal to 48V power supply
♦ Application requirements: 3.3V/5V, 1Mbps
Host
Controller
Hot Swap
Controller
Isolation
Ethernet
Switch/
Hub
INT/
SDA
SCL
INT/
SDA
SCL
RJ45
RJ45
RX
TX
21
Motor Control Isolation
♦ Many isolation paths - isolator, ISOdriver, current sensor opportunity
♦ High performance motors require precision timing from MCU to power devices
♦ Application requirements: short propagation delay, driving IGBT power devices
Motor Electronics Block Diagram
22
♦ Gateway box accepts external cable from telephone company
� TELCO cable subject to hazardous voltages
♦ Provides DSL, low-cost VoIP and higher-cost POTS service
♦ Safe system
� Metal connections on chassis are low voltage (SELV)
Typical Gateway Application
23
Gateway Installation with FXS, No USB
♦ Trade-off: FXS connection creates hazardous voltage path
� All circuitry now TNV-3
� CANNOT have exposed metal contacts outside box!
FXS connection
24
Gateway with FXS and USB
♦ Exposed metal on USB connector makes system unsafe
♦ Isolation must be added between exposed metal and TNV-3
Hazardous
voltage path
Non-Isolated Gateway w/FXS and USB
Isolated Gateway w/FXS and USB
♦ Isolation layer makes system safe!
� Gateway circuitry now SELV
Added isolation
25
Isolation Product in Power Delivery Sytems
VOUT
01
ISOLATED GATE DRIVE
SIGNAL
01
01
SECONDARYPOWER STAGES
PRIMARYPOWER STAGES
VIN
Si85xxCURRENTSENSORFamily
POWER
CONTROLLER
NON-ISOLATED DRIVERS
LOAD
Si82xxIso-Driver
Family
Si84xxIsolatorFamily
26
Isolation Applications Summary
Field Bus RS422/485 Others Inverter IPM
Defibrilator 〇〇〇〇Electrocardiograph (ECG/EKG) 〇〇〇〇Endoscopes 〇〇〇〇Esophagus Monitor (EPG) 〇〇〇〇Magnetic Resonance Imaging (MRI) 〇〇〇〇 〇〇〇〇Patient Monitoring 〇〇〇〇 〇〇〇〇X-Ray 〇〇〇〇 〇〇〇〇Automated Test Equipment 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇CPU Card 〇〇〇〇 〇〇〇〇 〇〇〇〇Elevator 〇〇〇〇 〇〇〇〇 〇〇〇〇Data Logging 〇〇〇〇 〇〇〇〇 〇〇〇〇Induction Cooker 〇〇〇〇 〇〇〇〇 〇〇〇〇Industrial Networking 〇〇〇〇 〇〇〇〇 〇〇〇〇Instrumentation 〇〇〇〇 〇〇〇〇 〇〇〇〇Motor Control 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Robotics 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇On-board Power Supply 〇〇〇〇Panel Switches 〇〇〇〇 〇〇〇〇 〇〇〇〇Prog. Logic Controller (PLC) 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Power Distribution 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Process Meter 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Remote Meter Reading
Servo Driver 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Sewing Machine 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Solar Generator 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Switch Mode Power Supply 〇〇〇〇 〇〇〇〇 〇〇〇〇Test & Measurement Equipment 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Thermo Counter/Recorder 〇〇〇〇 〇〇〇〇 〇〇〇〇Welding 〇〇〇〇 〇〇〇〇 〇〇〇〇
ADC/DAC
ADC/DAC, V/F
ADC/DAC
ADC/DAC
ADC/DAC
ADC/DAC
ADC/DAC, V/F
ADC/DAC
ADC/DAC
ADC/DAC
V/F
ADC/DAC
ADC/DAC
ADC/DAC
Digital Isolator or ISOdriver
Ind
ustr
ial
Med
ical
Market ApplicationVoltage
Monitor
A/D, D/A, or Voltage to
Freq. Conversion
Data Communication Driving Power Device
ADC/DAC
ADC/DAC, V/F
ADC/DAC, V/F
ADC/DAC, V/F
27
Isolation Applications Summary (cont.)
Inverter IPM Field Bus RS422/485 Others
Air Conditioning 〇〇〇〇 〇〇〇〇 〇〇〇〇Electronic Gaming 〇〇〇〇 〇〇〇〇Fitness Equipment 〇〇〇〇 〇〇〇〇 〇〇〇〇Induction Heating Cookers 〇〇〇〇 〇〇〇〇Musical Instrument Dig. Interface (MIDI) 〇〇〇〇Plasma Displays 〇〇〇〇Refrigerator 〇〇〇〇 〇〇〇〇 〇〇〇〇Washing Machines 〇〇〇〇 〇〇〇〇 〇〇〇〇PBX & Central Office 〇〇〇〇 〇〇〇〇 〇〇〇〇Power-Over-Ethernet (PoE) 〇〇〇〇 〇〇〇〇Telephone Switching Equipment 〇〇〇〇Telephone Terminal Equipment 〇〇〇〇Wireless Base Station 〇〇〇〇Elec. Cash Register, POS 〇〇〇〇 〇〇〇〇Isolated I/O 〇〇〇〇 〇〇〇〇Isolated USB 〇〇〇〇 〇〇〇〇Network 〇〇〇〇 〇〇〇〇Uninterruptible Power Supply (UPS) 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇Hybrid Electric Vehicle 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇 〇〇〇〇
Transportation System 〇〇〇〇 〇〇〇〇 〇〇〇〇
Digital Isolator or ISOdriver
Market ApplicationData CommunicationPower Device Drive Voltage
Monitor
Tra
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