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

nsp

ort

-

ati

on

Co

mp

uti

ng

&

Off

ice

Au

tom

ati

on

Co

nsu

me

rC

om

mu

nic

ati

on

s

www.silabs.com/power