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Introduction to Tertiary Telecom
Protection
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Outline
Tertiary Telecom Protection– Primary / Secondary / Tertiary– Transformer Coupled Applications– Tertiary Protection Requirements– Differential vs Rail Clamp Diode Array Protection– Driver Voltages & Vdrm vs Vs– Low Capacitance / Flat Capacitance
Littelfuse Tertiary Protection Products– P0080SAMC Family – SDP0242Q12F – SP03 Family– SP300x Family – SP3050 – Selection Table
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Building Entrance Line Card
Primary / Secondary / Tertiary Protection
Protection is a coordinated layering of protection technologies
Primary Protection
• OVP ~ 1000V• Thermal Overload• UL• NEBS • GR-974
Secondary Protection
• OVP ~ 300V• OCP ~ Fuse / PTC• GR-1089• UL 60950• ITU K.20 / K.21
Tertiary Protection
• OVP ~ 30V• No Regulatory Need
Outdoor Cabling
Tertiary protection is unique in that the performance requirements are dictated only by the customer’s perceived need.
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Transformer Coupled Applications
Tertiary protection circuits are
separated from the secondary protection
circuits by a transformer:
xDSL
T1 / E1
Ethernet
Tertiary protection is used to protect the signal driver circuitry. • T1/E1 circuits call this the transceiver. • xDSL circuits use line drivers. • Ethernet uses a PHY.
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Tertiary Protection Requirements
Tertiary protection requirements come from four considerations:– The nature of the threats to the protection scheme.
ESD only? Or AC Power Cross? Lightning Exposure?
– The amount of energy coupled through the transformer. Primary / Secondary Technology & Topology.
– The protection requirements of the protected driver circuitry. Operating Voltages / Damaging Voltages
– The nature of the datastream being protected. The Protection Scheme Must NOT Interfere!
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Rail Clamp Protection
Line Drivers
Transceiver
PHY
Po
wer S
up
ply
+V
-V
Digital Circuitry Surge Energy
Rail Clamp Protection Strategy:– Dump Energy Into Power Supply Rails
Through Steering Diodes Littelfuse offers several Rail Clamp Diode Arrays that combine
Steering and TVS diodes
Differential Energy: Through transformer magneticsCommon-Mode Energy: Through inter-winding capacitance.
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Differential Protection
Line Drivers
Transceiver
PHY
Po
wer S
up
ply
+V
-V
Digital Circuitry Surge Energy
Differential Protection Strategy:– Absorb Energy Directly
Differential Protection: Does not protect against common-mode energy Can not deliver energy to downstream components
Littelfuse offers several Differential Protection devices
for tertiary protection
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Driver Voltages & Protection Voltages
There are a variety of supply voltages for drivers:
Driver TypeTypical Power Rail
Voltage
Ethernet PHY 2.8, 3.3, 5.0
T1 / E1 / T3 5.0
xDSL (CPE End)
6, 7, 12
xDSL (CO End)
6, 12, 16, 20, 24
Two KEY Points…
• Protection VDRM or VRWM must be higher than the driver voltage.
• Relative protection effectiveness comes from comparing VC or VS on identical test waveforms.
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Capacitance Issues
High Capacitance will rob power from the signal.
Capacitance gains in importance as the data rate of the signal increases.– Non-Issue for Voice, T1/E1– Minor Issue for T3, ADSL– Major Issue for VDSL,
Ethernet Higher capacitance devices
should minimize how much their capacitance varies with applied voltage. – Use steering diodes– Use devices in series
SIDACtor Capacitance vs Line Voltage
0
10
20
30
40
50
60
70
80
90
100
0.1 1 10 100Line Voltage
pF
P0080SAMC
P0080SCMC
P0300SAMC
P0300SCMC
P0640SCMC
P2600SCMC
P3100SCMC
P3100D
P3500SCMC
There is a natural trade-off between surge capability, capacitance and clamp voltage:
High Surge High Capacitance Low Clamp Voltage
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Outline
Tertiary Telecom Protection– Primary / Secondary / Tertiary– Transformer Coupled Applications– Tertiary Protection Requirements– Differential vs Rail Clamp Diode Array Protection– Driver Voltages & Vdrm vs Vs– Low Capacitance / Flat Capacitance
Littelfuse Tertiary Protection Products– P0080SAMC Family – SDP0242Q12F – SP03 Family– SP300x Family – SP3050 – Selection Table
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P0080SAMC
Relatively high capacitance Low speed apps Very high surge capability Low voltage drivers only Pure differential protection SMB, QFN or TO-92 Packaging
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SDP0242Q12F
The only Littelfuse solution for drivers above 5V Pure differential protection Designed for VDSL applications
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SP03 Family
Available in 3.3V, 6 and 8V VRWM
Differential Protection Grounded Bridge Option 150A 8x20 Surge Rating SO-8 Packaging
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SP300x Family
Rail Clamp or Differential Protection Variety of SMT Packaging Ultra-Low Capacitance Limited Surge Capability
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SP3050
Rail Clamp or Differential Protection Good Parameter Balance:
– Mid-Capacitance– Mid-Surge
SOT23-6 Packaging
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Tertiary Protection Selection
Driver Voltage
Clamp Voltage
Surge Withstand
(8x20)
Capacitance(0V)
Circuit Configuration
P0080 Family
0 - 6V 25V(100V/uS)
150A 53pF Differential
SP300x 0 - 6V 10.6 – 11.8V(2A 8x20)
2.5 – 4.5A 0.35 – 0.50 pFRail Clamp Diode Array
SP3050 0 - 6V 13.2V(8A 8x20)
10A 1.2pFRail Clamp Diode Array
SP03-3.3
SP03-6
SP03-8
0 - 3.3V
0 - 6V
0 - 8V
18V - 22V(100A 8x20)
150A 8pFGrounded Diode
Array
SDP0242Q12F 0 - 24V 43V(100V/uS)
80A 15pF Differential
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Thank You!
Tertiary Telecom Protection
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