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Introduction to TVS Diode Arrays (SPATM Family)

Purpose– To introduce Littelfuse’s TVS Diode Arrays (SPATM Family) for

ESD and Lightning Protection

Objectives– Discuss the various threats that can affect electronic devices

and the standards used to evaluate their performance– Explanation of how protection devices operate– Discussion of key parameters commonly found in datasheets– Explanation of why silicon is the preferred protection technology– Examine the Littelfuse TVS Diode Array portfolio and how the

products are categorized

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ElectroStatic Discharge Protection

ESD is one of four major threats to electronic equipment and is the direct result of human interaction.

Lightning

AC Power Contact

Sustained Overload

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Triboelectric charging occurs when two materials make contact and separate Electrons from one material are transferred to another leaving one positively

charged and the other negatively charged.– The nature of the materials will determine who losses or gains electrons

The build up of static electricity is determined by several factors such as: area of contact, the speed of separation, relative humidity, and chemistry of the materials, surface work function, etc.

*Table from ESDA

What is ESD and where does it come from? – Triboelectric Charging

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ESD Standards – Human Body Model, MIL-STD

Based on Skin-to-Metal Contact– e.g. Person touches pin of IC, discharging directly to pins

Referenced in the Military Standard (883, Method 3015.7) test specification

Addresses the Manufacturing/Production environment; testing is done directly on the IC

Circuit Model:

Voltage Peak Current 500V 0.33A 1,000V 0.67A 2,000V 1.33A 4,000V 2.67A 8,000V 5.33A

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Based on Metal-to-Metal Contact– e.g. Person with tool/key in hand discharges to I/O port

Used in IEC 61000-4-2 test specification Addresses the user-environment; testing is done at the

application or system level Circuit Model:

Voltage Peak Current2,000V 7.5A4,000V 15.0A6,000V 22.5A8,000V 30.0A

ESD Standards – IEC 61000-4-2

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Discharge Voltage First Peak Current, 30ns Current, 60ns 2,000 V 7.5 A 4 A 2 A 4,000 V 15.0 A 8 A 4 A 6,000 V 22.5 A 12 A 6 A 8,000 V 30.0 A 16 A 8 A

Specified current values, per discharge voltage

Most all manufacturers test to 8kV or higher!

ESD Standards – IEC 61000-4-2 Waveform

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Peak current Peak currentDischarge Voltage Human Body Model IEC 61000-4-2 500 V 0.33 A 1,000 V 0.67 A 2,000 V 1.33 A 7.5 A 4,000 V 2.67 A 15.0 A 8,000 V 5.33 A 30.0 A

The key here is that a chipset that survives Human Body Model testing (in the manufacturing environment) is not guaranteed to survive in the field, where the exposure to ESD will be much more severe.

Different models yield much different peak current values; ultimately electrical stresses on the chipset are very different.

ESD levels in the field far exceed the values that can be generated in the manufacturing environment.

Comparing the Two Specifications – IEC 61000-4-2 vs. Human Body Model

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TVS Diode Arrays for ESD and Lightning Protection

Generally, 2 circuit types TVS Arrays

Typical capacitance range 3.5pF-30pF ESD Level: ±8kV to ±30kV Can be unidirectional or bidirectional

Diode Arrays Typical capacitance range 0.40pF-5pF ESD Level: ±8kV to ±30kV Can be unidirectional or bidirectional

Sizes range from 0201 to MSOP-10 Operating voltage up to 6VDC

Number of channels range from 1-14

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Time

Vo

ltag

e

Transient ESD

Circuit Damage Level

Clamping Level

Normal Operating Level

TVS Diode ArraysHow do they work?

GND

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Time

Vo

ltag

e

Transient ESD

Circuit Damage Level

Normal Operating Level

TVS Diode ArraysHow do they work?

GNDEnergy Dissipated in TVS

Clamping Level

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Bidirectional Unidirectional

TVS Diode ArraysWhat are the key parameters?

+I

+V-V

-I

IPP

IT

VR VBR VC

IR

+I

+V-V

-I

IPP

IT

VR VBR VC

IR

+I

+V-V

-I

IPP

IT

VR VBR VC

IR

+I

+V-V

-I

IPP

IT

VR VBR VC

IR

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+I

+V-V

-I

IPP

IT

VR

orVRWM

VBR VC

IR

Key Parameters: VR or VRWM

Reverse Standoff Voltage or

Reverse Working Maximum

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+I

+V-V

-I

IPP

IT

VR VBR VC

IR

Key Parameters: VBR

Breakdown Voltage

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+I

+V-V

-I

IPP

IT

VR VBR VC

IR

Key Parameters: Vc

Clamping Voltage

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Peak Pulse Current (Lightning Capability) For protection of telecom or broadband equipment lightning immunity is

just as important as ESD protection so for these devices the peak pulse current can be the driving factor.

The required level is often driven by regulatory standards such as Telcordia GR-1089, ITU, YD/T, IEC, etc

Common waveshapes (trxtd) are 2x10µs, 8x20µs, and 10x1000µs

Key Parameters: Peak Pulse Current (IPP)

Underground LineUnderground Line

Transients

Transients

Transients

Transients

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The figure below depicts a protection device as a variable resistor which will be high impedance (low leakage) during normal circuit operation and low impedance during any EOS (Electrical Over Stress) or ESD event.

The ultimate goal of a protection device is to provide the lowest resistance shunt path to GND under an ESD event to minimize the energy seen by the chipset or IC.

Ideally, all current would be steered into the ESD device so that the protected IC would not have to dissipate any of the energy input into the circuit.

Lower RDYN = Lower clamping voltage = Better, more robust protection

Key Parameters: Dynamic Resistance (RDYN)

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The dynamic resistance is the impedance value that the ESD suppressor represents as it switches from “off” to “on”

Using SP1005-01WTG as an example, we find:

This is the single best parameter to use in comparing ESD suppressors to determine which one is better!

Dynamic ResistanceHow it’s calculated

0.7Ω1A2A

9.3V10.0V

ΔI

ΔVRDYN

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Peak Voltage = 240V vs. 156V

Clamp Voltage = 75V vs. 16V

Data of Littelfuse’s SP1003-01DTG vs. a competitor varistor. Both devices have the same footprint (0402), same standoff voltage, and similar capacitances.

The area between the curves represents the amount of energy that DOES NOT get to the chip when this MLV was replaced by the SP1003-01DTG. The reduction in transient energy helps ensure that the chipset will survive even severe ESD events.

Dynamic ResistanceComparison of Competing Technologies

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Capacitance Low capacitance is needed in high-speed applications to minimize

signal degradation

A low capacitance device ensures the eye-diagram can stay within spec to prevent data corruption

Key Parameters: Capacitance

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General Purpose ESD Protection• Low-speed circuits (< 100Mbps) • Examples include power ports, keypads, buttons,

switches, audio, analog video, USB 1.1

Low Capacitance ESD Protection• High-speed data buses (> 100Mbps) • Examples include HDMI, USB 2.0, USB 3.0,

FireWire, DisplayPort, Ethernet, eSATA

Lightning Surge Protection• Specifically refers to Ethernet (10/100/1000) and

xDSL circuits in which there is a requirement to provide ESD and/or lightning surge protection (will vary by standard, customer, and application).

TVS Diode Arrays Product Categories

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General Purpose ESD Protection

Low Capacitance ESD Protection

Lightning Surge Protection

SP05 SP1001 SP1002 SP1003 SP1004 SP1005SP1006 SP1007 SP1010 SP1011 SP720 SP721 SP723 SP724 SP725

SP6001 SP6002

SP3001 SP3002 SP3003SP3004 SP3010 SP3011

SP3012

SP03-3.3 SP03A-3.3 SP03-6SPLV2.8 SPLV2.8-4 SP3050

SP4060 SP4061 SP4062SP4040

TVS Diode Arrays Product Categories

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System Level ESD Guide

Available on the Littelfuse website:– http://www.littelfuse.com/data/en/Technical_Articles/Littelfuse_ESD_System_Level_Guide.pdf

Discusses multiple applications such as:– USB1.1/2.0/3.0– HDMI– DVI– 10/100/1000 Ethernet– eSATA– 1394a/b– LVDS– Audio (Speaker/Microphone)– Analog Video– SIM Sockets– RS-485– CAN Bus– Keypad/Push button– LCD/Camera display interfaces

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Introduction to TVS Diode Arrays (SPATM Family)

Thank you!