TVS Diode Technology | Applications | RoHS Compliance | Selecting the Correct Part Type | Schematic Symbols | Definitions of Terms | Impulse Current Waveform | Mechanical Characteristics | Solderability | Preformed Lead Drawings | Part Marking | Part Numbering System

TVS Diode Technology

World Products Transient Voltage Suppression (TVS) Diodes are silicon avalanche devices designed, manufactured, specified and tested according to voltage suppression applications.

These devices, with their fast response and low clamping characteristics, protect all MOS technology based devices, hybrids, and other voltage sensitive components. The low clamping factor and pico-second response time of World Products TVS Diodes clamps transient pulses early and maintains them at an acceptable level for their entire duration. In other overvoltage protection devices, response times are delayed by 24nS to 2µs allowing transients to reach dangerous levels. World Products TVS Diodes are designed to meet a 1.30 maximum clamping factor at their rated peak impulse current. This can be compared to clamping factors of 2 to 5 found in other protection devices.

Applications

TVS Diodes are the optimum choice in protecting computer or data processor circuits and power supplies, airframe avionics and controls, numerically controlled machines, telecom circuits, and many other applications. These devices are designed to protect against transient voltages generated by lightning, electro-static discharge (ESD), and inductive switching.

RoHS Compliance

All axial TVS Diodes (no suffix code required) and SMD TVS Diodes (denoted by suffix “F”) products purchased from World Products, LLC. comply to a maximum concentration value of 0.1% by weight in homogeneous materials for lead (Pb), mercury, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) and of 0.01% weight in homogeneous materials for cadmium and are in compliance with Directive 2002/95/EC of the European Parliament and of the Council of 27 January 2003 on the restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS Directive).

Note:  Lead(Pb) in high-melting point solder for internal connections is not inhibited by RoHS. (i.e. tin-lead solder alloys containing more than 85%)

Selecting the Correct Part Type

The following guidelines should be observed in selecting the correct diode:

1. If the stand-off voltage is less than the operating voltage of the application, the diode will continually clamp the circuit voltage.
2. The Peak Pulse Current (IPPM) is the maximum current the TVS can handle. The source transient current is determined by dividing the peak transient voltage by the source impedance — this is often difficult to determine. In many cases, however, this may be obtained from industry standard documents, customer requirements, etc.
3. Determine the maximum voltage level that the protected device can withstand (VWS). Select a suppressor which will clamp the transient at a lower level (VC).

Consider the transient source: lightning, electro-static discharge, inductive switching or nuclear explosion (NEMP). Often, a 1500 watt peak pulse rated device will protect against transients due to secondary lightning effects or inductive switching on power, data and telephone lines. A 500 watt device is sufficient to protect sensitive components against transients generated by electro-static discharge.

VC Clamping Voltage:
Peak voltage across the suppressor measured at a specific IPPM. (Note: due to thermal, reactive or other effects, peak voltage and peak current are not necessarily coincident in time.)

IPP Peak Impulse Current:
Peak current measured using a specified waveform.

IPPM Rated Peak Impulse Current:
Rated maximum value of peak impulse current (IPP) applied using a 10 x 1000µs waveform. (Minimum of 10 pulses applied.)

Vwm Rated Standoff Voltage:
Maximum working (continuous) DC or peak voltage which may be applied over the standard operating temperature range. (Note: Vwm of a selected device must be greater than or equal to the maximum operating voltage of the line to be protected.)

ID Stand-By Current:
Maximum current that flows through the suppressor at rated standoff voltage (VWM) at a specified temperature.

VBR Breakdown Voltage:
The voltage measured across the suppressor at a specified DC test current (IT).

IT Test Current:
The specific DC current applied to the suppressor used to determine breakdown voltage (VBR).

VBR Temperature Coefficient:
The ratio of change in breakdown voltage (VBR) to changes in temperature. Expressed either as millivolts per degree centigrade (mV/°C) or percent change in breakdown voltage per degree centigrade (%VBR/°C).

CF Clamping Factor:
Ratio of the measured clamping voltage (Vc) at specified peak pulse current (IPP) to breakdown voltage (VBR) on a specific device.

         VC
CF = -----
         VBR

C Capacitance:
Capacitance between the two terminals of a suppressor measured at a specific frequency and bias voltage.

PPPM Rated Multiple Peak Pulse Power:
Derived by multiplying the maximum clamping voltage (VC) times the Rated Peak Impulse Current (IPPM).

IFSM Rated Forward Surge Current:
Unidirectional devices only. Maximum forward current during a 8.3ms half sine wave of AC line frequency (60Hz).

Impulse Current Waveform

Mechanical Characteristics

Case: UL94V-0 Molded Epoxy
Leads: Tinned Copper

Bending Terminal Leads (Through-hole) Types

When bending the leads, in order to avoid stress to the area where the leads enter the resinous body, use a tool that clamps the point between the package and the bending point. Improper bending will damage the die or separate the resin from the mounting frame, resulting in a degradation in electrical characteristics or a reliability problem such as poor resistance to moisture.

The leads must be bent only once and they should not be bent at an angle of more than 90°C. Leads must be formed before fixing them to a printed circuit board. Never form the leads after soldering.

Recommended distances are:
2mm for P4KE and SA series.
3mm for 1.5KE series.
4mm for 3KP, 5KP, 15KP, 20KP and 30KP series.

Solderability

Military Standard 202G, Method 208H

Heat Resistance of Solder

Note: For Lead-free solder, the maximum temperature during mounting processes will be 260°C for both re-flow and flow soldering processes.

Soldering of Through-hole Mounting Devices

Resistance to soldering heat test is carried out under the condition shown below. Soldering should be completed at a
lowest possible temperature for a shortest period.

Temp. 260± 5°C
Duration 10± 1s

General requirements for manual soldering are as follows:

• Use a soldering iron of 30 watts maximum, that is grounded or with a high insulation resistance.
• The iron tip is kept away from any resinous body.
• Attachment should be achieved in not more than 3 seconds.

Be sure again not to put an excessive mechanical stress on devices, such as a rough insertion of device into a throughhole, or manual reforming of leads after soldering.

Preformed Lead Drawings

Part Marking

Part Numbering System

AXIAL TYPE

SURFACE MOUNT

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