Circuit Isolation Techniques
& TI Isolation Technology
Industrial Interface Products
iif_bdm@list.ti.com
4Q 2013
Agenda
Technical Review
Markets and Applications
Competitive Advantages
Product
Q&A
TI Information – Selective Disclosure
Technical Review
Signal Isolation
The Real
World
mC
Speed
Position
Flow
TRANSCEIVERS
RS-485/ CAN
Pressure
Sound
ADC
ISOLATION
Temperature
PLC
DSP
Light
Humidity
TI Information – Selective Disclosure
DIGITAL INTELLIGENCE
Why is Isolation Used?
• Is a means of preventing DC or uncontrolled
transient current from flowing between two
communicating points.
• Is used in two general situations.
Isolation
1. Where there is the potential for voltage surges
that may damage equipment or harm humans
2. Where interconnections involve large ground
potential differences (GPDs) and disruptive
ground loops are to be avoided.
In both cases isolation is used to tolerate or protect from
hazardous voltages, yet allows for data or power flow between
the two points.
TI Information – Selective Disclosure
Different Isolation Techniques
Galvanic Isolation
•Isolated circuits exchange signals without DC current flow between the isolated domains.
Transformer Isolation
•A form of Galvanic isolation using transformers to provide an AC coupled data path with
coil separation providing the isolation.
•The same topology can also be used to transfer power.
Junction Isolation
•Typically found in low voltage applications.
•Highest breakdown processes available can reach 1200v (International Rectifier).
Amplifier Isolation
•Instrumentation Amplifiers and Differential Amplifiers comprise this area.
•High levels of Common Mode signal rejection (isolation) while maintaining or amplifying
the signals of interest.
•Typically low-voltage (10s of volts). Frequency dependency can be a weakness.
Wireless Technology
•Recently also focused on power transmission, “The Holy Grail” of power electronics.
•Dielectric thickness is variable and Frequency dependencies must be specified per
application.
TI
Information – Selective Disclosure
What is Isolation
Voltage
Supply 1
Voltage
Supply 2
1) Electrical Installation can cause large
GPDs (ground potential difference)
Circuit 2
between two remote nodes.
Circuit 1
ISOLATOR
Signal &
Signal & Return Path
Return Path
Ground Loop
2) A direct ground connection between the
nodes closes the ground loop.
3) Noise sources (i.e. electric motors)
injecting large currents into the ground
modulate the ground loop current.
4) This ground noise then appears in the
signal path.
5) An isolator breaks the ground loop, thus
removing signal path noise.
GPD
Ground 1
With
Isolation
No Isolation
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Ground 2 6) The GPD yet still exists and the isolator
must be robust enough to withstand the
large voltage differences.
Why Isolate?? - Other reasons
120 Ω
120 Ω
Data
SN65HVD233
CAN
CAN
SN65HVD233
Group loop
isolation
ISO
ISO7221C
ISO7221C
ISO
Noise
isolation
TMP101
Sensor
Fan
DSP
TMS 320 F2810
DSP
with CAN
Controller
DSP
120V
TI Information – Selective Disclosure
ADS1255
24-Bit
ISO7241A
OPA333
SN75477
LVC2G06
Amp
ISO
ISO
ISO721
Block High
Voltage
Amp
ISO
ISO7220M
Amp
Motor
480V
Data Isolation: Common-Mode
Transient Event
Signals referenced
to GND2
CMTI – The change in ground 1 relative ground 2. Measured in kV / μSec.
TI Information – Selective Disclosure
Isolation history
Capacitive
based isolation
Ewald Georg von Kleist invented the
first recorded capacitor 1745
Inductive
based isolation
Michael Faraday demonstrated the
transformer principle in 1831
Opto-coupler
based isolation
Zarlink Invented the
opto-coupler (1968)
Others…
Sound, RF, light,
Mechanical, etc
TI Information – Selective Disclosure
Isolation Techniques
Capacitive
Inductive
GMR
Optical
A. Capacitive
Capacitive
Inductive
GMR
Optical
ISO72X
ADuM1xx
IL7x
HCPL-07xx
CIO
1 pF
1 pF
Isolation
Dielectric
SiO2
Polyimide
Which is capacitive coupled?
B. Inductive
1.1 pF
C. GMR
D. Optical
Polyimide
0.6 pF
Mold
compound
E. All of the above
TI Information – Selective Disclosure
Source: TI App note SLLA198
www.ti.com/iso721
(Click on above link for web info)
Some History
“ Burr Brown Announces Industry-First Isolated Digital Coupler Using
Capacitive Barrier Technology.”
Article from: Business Wire Dated: August 19, 1998
Coplanar
Capacitor
Technology
Technical Innovation by TI with regard to capacitive isolation
technology improvements is impressive!!
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How are they constructed?
Cross Sectional View
Transmit
Chip Chip
Transmit
Receive
Chip
Receive
Chip
Mold compound
Bond wire
Top plate = Al
High Voltage
Capacitor Detail
Inter Level Dielectric
(Tons of SiO2)
Bottom Plate = Silicon Substrate (doped)
TI Information – Selective Disclosure
8-14 mm
Internal Construction
ISO72x: Integrated at
process level
Optical: Isolation functionality
added at package level
Inductive: Integrated at
process level
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How do they work?
Isolation Barrier
OSC
Low – Frequency
Channel
(DC...100 kbps)
LPF
PWM
VREF
OUT
IN
DCL
High – Frequency
Channel
(100 kbps...200Mbps)
VREF
 The LF channel assures correct output signal polarity during loss of input signal (i.e. wire-break)
 HF and LF channels use differential signaling for high noise immunity
 In the new architecture, all signal transitions go through the High-Frequency Channel.
TI Information – Selective Disclosure
High-Frequency Channel (50:50 duty cycle)
1
2
A
3
4
CLOCK TRANSFER
B
(Duty Cycle = 50:50 )
C
D
1
IN’
VREF
A
C
A
1.
2.
3.
4.
B
Initial Staging
RC Differentiator Stage
Comparator Stage
Flip Flop Stage
C
C
D
D
L
L
H
H
L
H
L
H
S
H
L
L
S
L
H
L
S = store previous condition
TI Information – Selective Disclosure
A
( IN’)
D
B
2
B
C
3
C
D
4
D
Low Frequency Channel
A
B
OSC
C
D
IN’
PWM
IN”
VREF
C
A
B
D
IN’
CLK
IN”
Between A and D, the LF-channel works
in the same way the HF channel does.
A
B
The only differences are the pulse-width
modulation at the beginning and the
demodulation at the end.
C
D
TI Information – Selective Disclosure
E
DEMOD
E
Terminology
Working or Operating Voltage (Vrms):
• Voltage that may be applied continuously across the Isolation barrier, ranges from 300Vrms to 1500Vrms
Isolation or Transient Voltage (Vrms):
• Voltage that may occur temporarily across the barrier tested for 1 minute during qualification.
• Ranges from 2.5kVrms to 6kVrms
Basic or Functional Isolation:
• Assumes a single level of isolation of certain strength
• Is applicable for most industrial applications and AC-equipment ≤ 400Vrms, and for consumer electronics.
• Is mostly rated at 560Vpk continuous, 4kVpk transient voltage.
Reinforced Isolation:
• Assumes a single level of isolation providing the same reliability as a two-layer isolation.
• Is applicable for most medical applications and AC-equipment > 400Vrms.
• For component-level reinforced rating, VDE requires certification testing at a 10 kVpk surge voltage level.
Common Mode Transient Immunity:
• CMTI is the quick change in Reference potential from primary to secondary.
• Given as the dV/dt up to which no false toggling of the output will occur (e.g. 35kV/us)
Partial Discharge (PD):
• Is a phenomena exhibited by insulator material when subjected to high electrical stresses, and is caused by the
localized dielectric breakdown of voids or imperfections present within, which does not immediately bridge the space
between two conductors.
• It is measured in pico-coulombs using ‘Apparent Charge’ method. 100% units are production-tested for PD.
• SiO2 is a very resilient insulation material.
TI Information – Selective Disclosure
Creepage and Clearance
Discusses the surface-distance that may conduct if wet/polluted, respectively the air-distance. For
560V/4kV mostly 5mm is sufficient, for 890V/6kV mostly 8mm is needed. Depends on pollution degree
Creepage distance
Clearance distance
Surface
Air
Shortest distance between two conductive
leads, across isolation barrier, measured
along surface of insulation.
Package/ designation
TI Package
Specs
Narrow body SOIC/ D
Gull wing / DUB
Wide body SOIC/ DW
TI Information – Selective Disclosure
QSOP / DBQ
Shortest distance between two conductive
leads , across isolation barrier, measured
through air.
Creepage mm
Clearance mm
4
4
6.8
6.1
8
8
3.7
3.7
Discovery Questions…
… to allow educated solution-proposals
1.
2.
Isolation strength:
basic/reinforced? What certifications?
Isolation & working voltage:
4kVpeak, 560Vpk continuous?
6kVpeak, 890Vpk continuous?
3.
Stand-alone isolation or integration
(Transceiver, Gate-Driver, Data-Converter)?
4.
Supply Voltages?
5.
Channel-count & channel direction?
6.
What is the transient immunity requirement? (CMTI)
TI Information – Selective Disclosure
Markets/Applications
TI Information – Selective Disclosure
Applications utilizing Isolation
Industrial:
• Robotics
• PLC input/output isolation
• Industrial networks
• Motor control
• Power supplies
Primary Task:
•Isolation between High-Power and Control Signals
•Isolation of Bus-Nodes to prevent Corruption
of the complete Bus & Common Mode Rejection
TI Information – Selective Disclosure
Applications utilizing Isolation
Medical:
Communications:
•
•
•
•
• PBX (Private Branch Exchange)
and central office
• Telephone terminal equipment
• Telephone switching equipment
• Modems
• ISDN
• Ethernet / PoE
Microwave therapy
Patient monitoring
Electrocardiographs
Defibrillators
Primary Task:
Communications:
•Isolation between Power and Caller
•Isolation of Bus-Nodes to prevent
Corruption of the complete Bus
TI Information – Selective Disclosure
Medical:
• Isolation between Power and Patient
Applications utilizing Isolation
Consumer Electronics:
•
•
•
•
Video (TV, VCR, etc.)
Plasma displays
Electronic gaming
Home appliances
Computers & Office Equipment
• Isolated I/O
• Printers and plotters
• Fax machines
Primary Task:
• Isolation between High-Power and User
TI Information – Selective Disclosure
Competitive Analysis
TI Information – Selective Disclosure
Specs and Reliability Comparison
Opto
(Avago)
Magnetic
(ADI)
Capacitive
(Si Labs)
Capacitive
(TI)
Max Data Rate (Mbps)
50
150
150
150
Typ Power Consumed/Ch @ 25Mbps & 3.3V (mA)
16
3.4
2.7
2
Max Propagation Delay Time (ns)
22
32
13
12
Pulse Width Distortion (ns)
2
2
4.5
1.5
Channel-to-Channel skew (ns)
16
2.0
2.5
1.6
Part-to-Part Skew (ns)
20
10
4.5
2
ESD on all Pins (kV)
±2
±2
±4
±4
Minimum CM Transient Immunity (kV/us)
20
25
25
25
-45..125
-40..125
-40..125
-40..125
6.92E+04
3.17E+07
-
1.65E+09
14391
31.55
-
0.6
Radiated Electromagnetic-Field Immunity
IEC61000-4-3 (80MHz-1000MHz)
MIL-STD 461E RS103 (30MHz-1000MHz)
-
Fails*
Fails*
Fails*
Fails*
Complies
Complies
High-Voltage Lifetime Expectancy (yrs)
-
< 10
> 60*
> 28
Temperature Range (oC)
MTBF @ 125oC, 90% Confidence (Hrs)
FIT@ 125oC, 90% Confidence (per 1E+09 hrs)
* Devices passed the minimum criteria set by some standards. See details later in the presentation.
TI Information – Selective Disclosure
Competitive Analysis – ICC1
ICC1 COMPETITIVE ANALYSIS @ 3.3V
35
30
ICC1 (mA)
25
ISO7641FM
20
ISO7641FC
Si8641BD
15
ADuM4401C
10
5
0
0
25
50
75
100
125
150
Data Rate (Mbps)
 TI Isolators have excellent power consumption throughout its operating range.
 Data shown above is taken in the lab on the same setup to ensure apples-toapples comparison.
TI Information – Selective Disclosure
Competitive Analysis – ICC2
ICC2 COMPETITIVE ANALYSIS @ 3.3V
30
25
ICC2 (mA)
20
ISO7641FM
ISO7641FC
15
Si8641BD
ADuM4401C
10
5
0
0
25
50
75
100
125
150
Data Rate (Mbps)
 TI Isolators have excellent power consumption throughout its operating range.
 Data shown above is taken in the lab on the same setup to ensure apples-toapples comparison.
TI Information – Selective Disclosure
Competitive Analysis – Propagation Delay
Propagation Delay @ 3.3V
35.00
Prop Delay (ns)
30.00
25.00
ADuM4401C
20.00
Si8641BD
ISO7641FC
15.00
ISO7641FM
10.00
5.00
0.00
Device Type
 TI has isolators with very fast propagation delays (M-grade) and devices with
integrated input noise filters (C-grade).
 Data shown above is taken in the lab on the same setup to ensure apples-toapples comparison.
TI Information – Selective Disclosure
Dielectric Materials Used for Isolation
• SiO2: ISO72x Typical BV is 800 Vpeak/um
– Inorganic
– Highly Stable (over temperature, moisture, time), high quality
– Used extensively and for long time as dielectric in semiconductor
(low defect rates)
– Deposited in a controlled semiconductor process
• Polyimide: ADI Transformer core Typical BV is 250 Vpeak/um
– Organic
– Retains moisture – affects lifetime especially at high voltages
– Used in semiconductor mainly for stress relief & now as isolation
barrier
• Epoxy: Opto-couplers: Typical BV is 50 Vpeak/um
– Uses filler materials
– Leaky (higher partial discharge)
– Applied at packaging as mold compound
– Voids and anomalies are common
TI Information – Selective Disclosure
High Voltage Lifetime – TDDB
(time dependent dielectric breakdown)
TI Information – Selective Disclosure
High Voltage Lifetime
Temperature and Voltage Effect
Tj = 150C
70
Lifetime in Years
60
Tj = 100C
Tj = 85C
59
50
43
40
30
31
28
20
23
20
15
11
10
0
500
600
700
800
Vpeak (Working Voltage)
TI Information – Selective Disclosure
900
1000
E-field immunity Test Report
TI Information – Selective Disclosure
EN55022 Class B Radiations Testing
1Mbps: Comparison of Radiated Noise Spectrum – Antenna Horizontal
ADuM1201: 1Mbps
operation @ 5V Vcc
ISO7221: 1Mbps
operation @ 5V Vcc
TI Information – Selective Disclosure
EN55022 Class B Radiation Testing
25Mbps: Comparison of Radiated Noise Spectrum – Antenna Horizontal
ADuM1201: 25Mbps
operation @ 5V Vcc
ISO7221: 25Mbps
operation @ 5V Vcc
TI Information – Selective Disclosure
E-field susceptibility Test Report
TI
Isolator
ADI
Isolator
TI Information – Selective Disclosure
Roadmap and Products
(Click Link for presentation)
TI Information – Selective Disclosure
Thank You!