Resistors FAQ

Compliance Management

Can I download RoHS, REACH, MSL, life cycle and similar data for all your products in one go?

Yes, in addition to looking up this information for individual products, you can download an Excel compatible matrix for the whole product range: Compliance, Processing & Lifecycle Matrix. This link, and further information may be found on the Product Compliance page.

Can I get IPC1752 material composition for a resistor?

Yes, IPC1752 material composition declarations are available on request. Please use IPC1752 Enquiry with the relevant series entered to request this information.

Can I get the latest EICC CMRT for Conflict Mineral reporting?

Yes, the latest Conflict Mineral reports are available on the Product Compliance page, one for our Bedlington site and one for our Corpus Christi site. If you are uncertain which site is relevant, search for the relevant product, click on the Type and select the Compliance tab, then download the report. This will be the correct report for the product you have selected.

How can I check for SVHC content?

Search for the relevant product, click on the Type and select the Compliance tab. This shows the REACH status and the latest number of SVHCs covered, and a certificate can be downloaded.

How can I find a resistor's REACH status?

Search for the relevant product, click on the Type and select the Compliance tab. This shows the REACH status and the latest number of SVHCs covered, and a certificate can be downloaded.

How can I find a resistor's RoHS status and certificate?

Search for the relevant product, click on the Type and select the Compliance tab. This shows the RoHS status of Pb-free version and how to identify whether a part number is Pb-free. The relevant RoHS certificate can also be downloaded.

How can I tell if a part number is for a Pb-free version, and what termination finish is used?

Search for the relevant product, click on the Type and select the Compliance tab. The first section shows information on Pb-free finish and how part numbers show this status.

How do I request an IMDS entry for a resistor?

Please request this information by using IMDS Enquiry with the relevant series entered.

Component Certification

What products have AEC-Q200?

Products with AECQ200 may be found here.

What products have CECC release or MIL approvals?

Products with CECC release may be found here, and those with MIL approvals here.

What products have DSCC drawings?

Products with DSCC drawings may be found here.

What products have UL recognition?

Products with UL recognition may be found here.

Export Control

Can I find out the country of origin for a resistor?

Please request this information by using Country of Origin Enquiry with the relevant series entered.

Can I get the ECCN commodity code or HTS code for a resistor?

Please request this information by using Export Control Enquiry with the relevant series entered.

How can I establish the ITAR status of a resistor?

Please request this information by using ITAR Enquiry with the relevant series entered.

General

Can you help me to understand the definitions of technical terms used on your datasheets?

Yes, please look at Definitions of Technical Terms. If you need further help, please send a Technical Enquiry.

How do I find a resistor datasheet?

Enter the series or type in the Product Data Search box and click on the related PDF icon.

How do I read the colour code / color code on a resistor?

The resistor colour code / color code description may be found here.

How do I read the EIA-96 value code (2 digits & 1 letter) on a small chip resistor?

The EIA-96 value codes are listed here.

What products are available in SnPb / leaded / pure tin free terminations?

Products with SnPb terminations are listed here.

What standard resistance values are available?

Consult the Electrical Data part of the product datasheet. In most cases this will specify the standard value series, often E24 or E96. This refers to EIA standard resistor values listed here. Low ohmic value products are often additionally available in integer values up to 10 milliohms and in multiples of 5 milliohms. Some products are available only at a limited set of values listed on the datasheet.

What is an infallible resistor?

An infallible resistor, within the field of Intrinsically Safe (IS) design, is defined as one for which a short circuit failure mode is considered impossible, and therefore need not be simulated during analysis or testing. It is used for the function of limiting the current which may pass through barriers designed to restrict energy transfer between parts of an IS system. As it is a potential dissipator of heat, it is generally derated by at least 50% in order to limit maximum surface temperature. When the level of protection requires the resistors to be doubled or tripled, they are connected in series.

The technology preferred for this is wirewound, since this is essentially like a conventional wire link fuse, albeit with the wire wound around an insulated rod. For such a part the failure modes may be parametric (+/- a few percent ohmic value change) or open circuit.

An example of a products series which may be suitable for this is ULW.

Life Cycle Management

How do I find out the life cycle status or estimated EOL of a resistor?

Search for the relevant product, click on the Type and select the Life Cycle tab. This indicates whether a product is Growth, Mature, Decline, NRND or Obsolete. An estimate of number of years to EOL is also given.

Where can I get information on obsolete resistors?

Many obsolete components are included on this website, although they are excluded from parametric or category search results . You can find them by entering the product series or type in the Product Data Search box. In the results, the Basic tab gives brief data and the datasheet, and the Life Cycle tab gives EOL date, PCN download and suggested replacement product where available.

Manufacturing

What storage conditions are recommended and what shelf life time do the resistors have?

No shelf life is defined as such, but in general, solderable parts should be tested for solderability before use if over 2 years old. Detailed advice on shelf life and storage conditions is given here.

Where can I find out compatible wave soldering conditions?

Search for the relevant product, click on the Type and select the Processing tab. This indicates whether a part is compatible with wave soldering, and any conditions which apply.

Where can I find out the MSL (Moisture Sensitivity Level) of SMD resistors?

Search for the relevant product, click on the Type and select the Processing tab. This indicates MSL for reflow compatible products.

Where can I find out the reflow conditions of SMD resistors?

Search for the relevant product, click on the Type and select the Processing tab. This indicates reflow compatibility.

Purchasing

Can I find the current leadtime for a resistor?

Please request this information by using Leadtime Enquiry with the relevant series entered.

Do you have a cross reference list or table of equivalents for resistors from alternative sources?

Yes, this is built in to our website and may be accessed by entering the alternative source type or part number in the Cross Reference Search box. This will generate suggestions as you type, which may be selected as required. Generally only the type or part number prefix is required.

How can I check availability of stock?

Most stock available to purchase is with our franchised distributors, and may be located by entering the part number in the Distributor Stock Check box. If you do not find what you are looking for, please make a Stock Availability Enquiry with the full part number(s).

How can I check on the status of a delivery?

You can make a Delivery Status Enquiry to our Customer Service team.

How can I check on the status of an order?

You can make an Order Status Enquiry to our Customer Service team.

How can I contact my local sales contact, franchised distributor or rep agency?

Contact details for our sales offices and franchised distributors in each region, together with manufacturers' representatives for USA, may be found on the sales page.

How can I request an expedite on my order?

You can make a Expedite Request Enquiry to our Customer Service team.

How do I get hold of samples for a prototype or pre-production build?

The fastest way to get samples is normally to use one of our franchised distributors. You can search for stock by entering the part number in the Distributor Stock Search box. If you cannot find what you need then you can send our Sales team a Sample Request Enquiry.

Where should I send my RFQ?

You can send an RFQ Enquiry to our Sales team.

Quality

Can I see your company's ISO14001 environmental management system certificates?

Yes, our ISO14001 environmental management system certificates may be downloaded here.

Can I see your company's ISO9001 / TS16949 quality management system certificates?

Yes, our ISO9001 / TS16949 quality management system certificates may be downloaded here.

Can I see your company's OHSAS 18001 occupational health and safety management system certificates?

Yes, our OHSAS 18001 occupational health and safety management system certificates may be downloaded here.

How can I find out when a PCN has been issued?

To check for existing PCNs on a product, search for the relevant product, click on the Type and select the Life Cycle tab. This will contain a link to related PCNs if any exist. To be informed immediately of PCNs in the future, sign up by going to the Talk to Us box, selecting Sign Up, entering your details and selecting PCNs.

How can I report a quality concern?

You can send our Quality team Quality Concern Enquiry.

How can I request a CAR (Corrective Action Report) for a quality concern I have?

You can send our Quality team a CAR Enquiry.

How can I request an 8D Report for a quality concern I have?

You can send our Quality team an 8D Report Enquiry.

How can I request an RMA number in order to return parts?

You can send our Quality team an RMA Request Enquiry.

R&D / Design

Can I do a parametric search by value, ratings and precision?

Yes, by going to the Products Page and entering one or more values in the parameter boxes on the right and clicking on Search. This type of search may be further refined by selecting the required category (mounting, package etc.) When there are 15 or fewer results, or when you click on Show Selected, the results table is displayed.

Can you supply FIT rate data for a product?

For many products sufficient reliability test data has been accumulated to allow calculation of FIT rate, and this may be requested by sending a FIT Enquiry to our Applications team.

Can you supply MTBF data for a product?

For many products sufficient reliability test data has been accumulated to allow calculation of MTBF, and this may be requested by sending an MTBF Enquiry to our Applications team.

Can you supply reliability data for a product?

For many products sufficient reliability test data has been accumulated to allow calculation of FIT rate, and this may be requested by sending a Reliability Enquiry to our Applications team.

Do you have products for high temperature applications?

Yes, products for high temperature operation may be found here.

Do you provide 3D drawings / STP / STEP design models?

Yes, selected products have 3D drawing data. To find this search for the relevant product, click on the Type and select the Related Literature tab.

How are voltage, current, power and resistance related?

The resistance value of a resistor is defined as the ratio of the voltage across it to the current through it. The power dissipated is the product of voltage and current. A Resistance Calculator is available where you can enter any two known values, and the remaining two values are calculated.

How do I calculate Ohm's law?

Ohm's Law states that resistance is the voltage across a resistor divided by the current flowing through it. A Resistance Calculator is available which calculates all current, voltage and resistance values.

How do I calculate the power rating for high temperature operation?

The power rating on a datasheet applies at ambient temperatures up to the rated temperature (e.g. 1W at 70°C). For higher ambient temperatures the resistor is de-rated, often linearly, to zero power at a temperature stated on the datasheet. This de-rating information is either given as a de-rating graph, or as a statement in the Performance Data section. A Temperature Derating Calculator is also available.

How do I calculate the value of a bleed resistor for safe capacitor discharge?

Safe capacitor discharge is defined in terms of initial charge voltage, safety threshold voltage and maximum allowed discharge time. Knowing these factors, the maximum bleed resistance for a given capacitor value (at maximum upper tolerance) may be calculated using the Capacitor Discharge Calculator.

How do I get hold of samples for my design prototype?

The fastest way to get samples is normally to use one of our franchised distributors. You can search for stock by entering the part number in the Distributor Stock Search box. If you cannot find what you need then you can send our Sales team a Sample Request Enquiry.

How do I know whether power rating or limiting element voltage applies for a specific resistor?

A parameter called critical resistance is stated on the Technical tab of the information page for most product types. Below the critical resistance the rated power is the limiting factor, whilst above it the limiting element voltage is the limiting factor. A Limiting Factor Calculator may be used to determine the actual maximum voltage and power for given ratings and resistance value.

How do I relate the pulses or surges in my design to the data on your datasheet?

Datasheets give surge energy capacity for wirewound or bulk metal types and peak power versus duration for film types. Testing normally relates to rectangular pulse shapes. A Pulse Calculator is available to help you relate datasheet pulse data to your application circuit.

How do I request FAE support for product selection or customisation?

You can send out Applications team an FAE Support Enquiry.

What tools exist to help me choose the correct resistor for my design?

You can go to the Products Page and search our entire range by parameters (resistance value, ratings and precision) and by required category (mounting, package etc.) When there are 15 or fewer results, or when you click on Show Selected, the results table is displayed. Alternatively, a quick overview of our product portfolio is available in our Shortform Catalogue and in application notes on the Literature Page.

What is the definition of ambient temperature, maximum (°C)?

The maximum ambient temperature which the component is designed to withstand for continuous operation. Also known as Upper Category Temperature (UCT). (See Rated Ambient Temperature for a definition of ambient temperature.)

What is the definition of best TCR (± ppm/ °C)?

The highest precision grade of TCR offered, which may apply to a restricted ohmic value range. TCR (Temperature Coefficient of Resistance) is defined as the maximum magnitude of reversible ohmic value change per degree centigrade due to deviation in body temperature from a reference normally of 20°C. In the case of arrays and networks, the TCR given here is tracking TCR; see datasheet for absolute TCR.

What is the definition of best tolerance (± %)?

The highest precision grade of tolerance offered, which may apply to a restricted ohmic value range. Tolerance is defined as the maximum allowable magnitude of deviation from nominal ohmic value measured at delivery and at room temperature. In the case of arrays and networks, the tolerance given here is ratio tolerance; see datasheet for absolute tolerance.

What is the definition of critical resistance (Ω)?

The resistance value at which application of the Limiting Element Voltage causes dissipation of the full Rated Power. At ohmic values below this, the Rated Power is the limiting factor which restricts electrical loading, whilst at ohmic values above this, the Limiting Element Voltage is the limiting factor. A Limiting Factor Calculator is available to determine critical resistance and which rating matters for a specific resistor.

What is the definition of derate to 0W temperature (°C)?

The temperature at which the derating curve meets zero watts. This normally equals the Maximum Ambient Temperature, but for some power resistors, may exceed it. Derating is normally linear from full Rated Power at Rated Ambient Temperature, unless the datasheet states otherwise. A Temperature Derating Calculator is available to assist in calculations.

What is the definition of isolation voltage (V)?

The maximum continuous voltage which may be applied between the resistor and a conductor in contact with its insulated body.

What is the definition of limiting element voltage (V)?

The maximum continuous voltage which may be applied across a resistor whose ohmic value is greater than or equal to the critical resistance. Also known as Maximum Working Voltage. Usually it is DC or AC rms, but the datasheet for high voltage parts may define it as DC or AC peak.

What is the definition of power rating (W)?

The maximum continuous power that may be dissipated by a resistor whose ohmic value is less than or equal to the Critical Resistance and at or below the Rated Ambient Temperature. Also known as Rated Power. In the case of arrays and networks, the rating given here is per resistor element; see datasheet for package rating.

What is the definition of rated ambient temperature (°C)?

The highest ambient temperature at which the full Rated Power may be dissipated. Ambient temperature is defined as the temperature which would be adopted by the body of the resistor under application conditions except with negligible power dissipation in the resistor. For through-hole packages this is usually air temperature, for heatsink mounted packages it is heatsink temperature, and for SMD packages it is local PCB temperature.

What is the definition of resistance, maximum (Ω)?

The maximum ohmic value available in the standard range.

What is the definition of resistance, minimum (Ω)?

The minimum ohmic value available in the standard range.

Do you have pulse or surge data for your products?

Several products are specified for pulse and surge applications, and these have data on the datasheet. For bulk metal and wirewound types this is given as an energy rating in Joules. For film types it is a graph of peak power versus duration. Additional data for wirewound resistors is given in an Application Note.

What is the definition of single pulse data?

Single pulse data relates to a situation where a resistor sees a momentary high power dissipation for a short duration, normally below 100ms, and where this is either an isolated event, or repeated infrequently such that the mean dissipated power is much less than the rated power. If mean power dissipation is significant, refer to continuous pulse data. A Pulse Calculator is available to help you relate datasheet pulse data to your application circuit.

What is the definition of continuous pulse data?

Continuous pulse data relates to a situation where a resistor sees a momentary high power dissipation for a short duration, normally below 100ms, and where this is repeated such that the mean dissipated power is equal to the full rated power. If the application requires a mean power dissipation less than this, the pulse power limit can be derived by interpolation between this and the single pulse data. A Pulse Calculator is available to help you relate datasheet pulse data to your application circuit.

Can I get an Approval Test Report for a product?

In most cases test data is available on request, and you may use a Test Report Request Enquiry for this purpose.