Organization and Basis of Presentation (Policy)	9 Months Ended
Oct. 28, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying interim Unaudited Consolidated Condensed Financial Statements of Semtech Corporation and its subsidiaries have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of the Company, these unaudited statements contain all adjustments (consisting of normal recurring adjustments) necessary to present fairly, in all material respects, the financial position of Semtech Corporation and its subsidiaries for the interim periods presented. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations, and the Company believes that the included disclosures are adequate to make the information presented not misleading. In March 2012, the Company completed the acquisitions of Gennum Corporation (“Gennum”) and Cycleo SAS (“Cycleo”). The Unaudited Consolidated Condensed Financial Statements include the results of operations of Gennum and Cycleo commencing as of the acquisition dates. See Note 2 for further discussion. These Unaudited Consolidated Condensed Financial Statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s latest annual report on Form 10-K. The results reported in these Unaudited Consolidated Condensed Financial Statements should not be regarded as necessarily indicative of results that may be expected for any subsequent period or for the entire year.
Fiscal Year	Fiscal Year The Company reports results on the basis of 52 and 53 week periods and ends its fiscal year on the last Sunday in January. The other quarters generally end on the last Sunday of April, July and October. All quarters consist of 13 weeks except for one 14-week period in 53-week years. The third quarter of fiscal years 2013 and 2012 each consisted of 13 weeks.
Segment Information	Segment Information The Company operates and accounts for its results in one reportable segment. The Company designs, develops, manufactures and markets high performance analog and mixed signal integrated circuits. The Chief Executive Officer has been identified as the Chief Operating Decision Maker as defined by guidance regarding segment disclosures.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Interest Rate Derivative	Interest Rate Derivative The Company manages interest expense using variable rate debt. To manage its interest rate risk, the Company occasionally hedges the future cash flows of its variable rate debt, principally through interest rate contracts with major financial institutions. Interest rate cap contracts involve the receipts of variable amounts from a counterparty when one-month LIBOR exceeds the capped interest rate in exchange for an upfront payment from the Company, capping the Company’s one-month LIBOR floating interest payments at the strike rate on its interest rate cap contract. Interest rate contracts that meet specific criteria are accounted for as cash flow hedges in accordance with the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification (“ASC”) Topic 815, Derivatives and Hedging. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income, net of taxes, and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings.
Earnings Per Share	Basic earnings per common share is computed by dividing income available to common shareholders by the weighted-average number of shares of common stock outstanding during the reporting period. Diluted earnings per common share incorporates the incremental shares issuable, calculated using the treasury stock method, upon the assumed exercise of stock options and the vesting of restricted stock.
Revenue Recognition	Revenue Recognition The Company recognizes product revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collectability is probable. Recovery of costs associated with product design and engineering services are recognized during the period in which services are performed. The product design and engineering recovery, when recognized, will be reported as a reduction to product development and engineering expense. Historically, these recoveries have not exceeded the cost of the related development efforts. The Company includes revenue related to granted technology licenses as part of “Net sales.” Historically, revenue from these arrangements has not been significant though it is part of our recurring ordinary business. In the third quarter of fiscal year 2013, the Company entered into a single licensing arrangement that resulted in the recognition of $7.5 million of revenue. The Company defers revenue recognition on shipment of products to certain customers, principally distributors, under agreements which provide for limited pricing credits or return privileges, until these products are sold through to end-users or the return privileges lapse. For sales subject to certain pricing credits or return privileges, the amount of future pricing credits or inventory returns cannot be reasonably estimated given the relatively long period in which a particular product may be held by the customer. Therefore, the Company has concluded that sales to customers under these agreements are not fixed and determinable at the date of the sale and revenue recognition has been deferred. The Company estimates the deferred gross margin on these sales by applying an average gross profit margin to the actual gross sales. The average gross profit margin is calculated for each category of material using standard costs which is expected to approximate actual costs at the date of sale. The deferred gross margin does not include any adjustments for sales returns. The estimated deferred gross margins on these sales, where there are no outstanding receivables, are recorded on the Unaudited Consolidated Condensed Balance Sheets under the heading of “Deferred revenue.” The Company records a provision for estimated sales returns in the same period as the related revenues are recorded. The Company bases these estimates on historical sales returns and other known factors. Actual returns could be different from Company estimates and current provisions for sales returns and allowances, resulting in future charges to earnings.
Share-based Compensation, Option and Incentive Plans	Share-based Payment Arrangements The Company has various equity award plans that provide for granting stock-based awards to employees and non-employee directors of the Company. The plans provide for the granting of several available forms of stock compensation. As of October 28, 2012, the Company has granted options and restricted stock under the plans and has also issued some stock-based compensation outside of the plans, including options and restricted stock issued as inducements to join the Company. Grant Date Fair Values and Underlying Assumptions; Contractual Terms The Company uses the Black-Scholes pricing model to value options. For awards classified as equity, stock-based compensation cost is measured at grant date, based on the fair value of the award, and is recognized as an expense over the employee’s or director’s requisite service period. For awards classified as liabilities, stock-based compensation cost is measured at fair value at the end of each reporting date until the date of settlement, and is recognized as an expense over the employee’s or director’s requisite service period. Expected volatilities are based on historical volatility using daily and monthly stock price observations.
Investments	Investments that have original maturities of three months or less are accounted for as cash equivalents. This includes money market funds, time deposits and U.S. government obligations. Temporary and long-term investments consist of government, bank and corporate obligations, and bank time deposits with original maturity dates in excess of three months. Temporary investments have original maturities in excess of three months, but mature within twelve months of the balance sheet date. Long-term investments have original maturities in excess of twelve months. The Company determines the cost of securities sold based on the specific identification method. Realized gains or losses are reported in “Interest income and other expense, net” on the Unaudited Consolidated Condensed Statements of Income. The Company classifies its investments as “available for sale” because it may sell some securities prior to maturity. The Company’s investments are subject to market risk, primarily interest rate and credit risks. The Company’s investments are managed by a limited number of outside professional managers that operate within investment guidelines set by the Company. These guidelines include specified permissible investments, minimum credit quality ratings and maximum average duration restrictions and are intended to limit market risk by restricting the Company’s investments to high quality debt instruments with relatively short-term maturities.
Fair Value of Financial Instruments	When determining the fair value measurements for assets and liabilities required or permitted to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance. The Company uses the following three levels of inputs in determining the fair value of the Company’s assets and liabilities, focusing on the most observable inputs when available: Level 1 - Quoted prices in active markets for identical assets or liabilities. Level 2 - Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets with insufficient volume or infrequent transactions (less active markets); or model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Unobservable inputs to the valuation methodology that is significant to the measurement of fair value of assets or liabilities. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level in the fair value hierarchy within which the fair value measurement is disclosed is determined based on the lowest level input that is significant to the fair value measurement.
Goodwill and Intangible Assets, Goodwill	Goodwill is not amortized, but is tested for impairment using a two-step method on an annual basis and whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The recoverability of goodwill is measured at the reporting unit level by comparing the reporting unit’s carrying amount, including goodwill, to the fair market value of the reporting unit. The fair value of goodwill is tested for impairment on a non-recurring basis in the accompanying Unaudited Consolidated Condensed Financial Statements using Level 3 inputs.
Goodwill and Intangible Assets, Intangible Assets	Purchased intangibles are amortized on a straight-line basis over their estimated useful lives. In-process research and development is recorded at fair value as of the date of acquisition as an indefinite-lived intangible asset until the completion or abandonment of the associated research and development efforts or impairment. Upon completion of development, acquired in-process research and development assets are transferred to finite-lived assets and amortized over their useful lives.
Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived	The Company reviews indefinite-lived intangible assets for impairment annually or whenever events or changes in circumstances indicate the carrying value may not be recoverable. Recoverability of indefinite-lived intangible assets is measured by comparing the carrying amount of the asset to the future discounted cash flows the asset is expected to generate. Acquired in-process research and development will be tested for impairment on a non-recurring basis in the accompanying consolidated financial statements using Level 3 inputs.

Organization and Basis of Presentation (Policy)

9 Months Ended

Oct. 28, 2012

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accompanying interim Unaudited Consolidated Condensed Financial Statements of Semtech Corporation and its subsidiaries have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of the Company, these unaudited statements contain all adjustments (consisting of normal recurring adjustments) necessary to present fairly, in all material respects, the financial position of Semtech Corporation and its subsidiaries for the interim periods presented. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) have been condensed or omitted pursuant to such rules and regulations, and the Company believes that the included disclosures are adequate to make the information presented not misleading.

In March 2012, the Company completed the acquisitions of Gennum Corporation (“Gennum”) and Cycleo SAS (“Cycleo”). The Unaudited Consolidated Condensed Financial Statements include the results of operations of Gennum and Cycleo commencing as of the acquisition dates. See Note 2 for further discussion.

These Unaudited Consolidated Condensed Financial Statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s latest annual report on Form 10-K. The results reported in these Unaudited Consolidated Condensed Financial Statements should not be regarded as necessarily indicative of results that may be expected for any subsequent period or for the entire year.

Fiscal Year

The Company reports results on the basis of 52 and 53 week periods and ends its fiscal year on the last Sunday in January. The other quarters generally end on the last Sunday of April, July and October. All quarters consist of 13 weeks except for one 14-week period in 53-week years. The third quarter of fiscal years 2013 and 2012 each consisted of 13 weeks.

Segment Information

The Company operates and accounts for its results in one reportable segment. The Company designs, develops, manufactures and markets high performance analog and mixed signal integrated circuits. The Chief Executive Officer has been identified as the Chief Operating Decision Maker as defined by guidance regarding segment disclosures.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Interest Rate Derivative

The Company manages interest expense using variable rate debt. To manage its interest rate risk, the Company occasionally hedges the future cash flows of its variable rate debt, principally through interest rate contracts with major financial institutions. Interest rate cap contracts involve the receipts of variable amounts from a counterparty when one-month LIBOR exceeds the capped interest rate in exchange for an upfront payment from the Company, capping the Company’s one-month LIBOR floating interest payments at the strike rate on its interest rate cap contract. Interest rate contracts that meet specific criteria are accounted for as cash flow hedges in accordance with the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification (“ASC”) Topic 815, Derivatives and Hedging.

The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income, net of taxes, and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings.

Earnings Per Share

Basic earnings per common share is computed by dividing income available to common shareholders by the weighted-average number of shares of common stock outstanding during the reporting period. Diluted earnings per common share incorporates the incremental shares issuable, calculated using the treasury stock method, upon the assumed exercise of stock options and the vesting of restricted stock.

Revenue Recognition

The Company recognizes product revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collectability is probable. Recovery of costs associated with product design and engineering services are recognized during the period in which services are performed. The product design and engineering recovery, when recognized, will be reported as a reduction to product development and engineering expense. Historically, these recoveries have not exceeded the cost of the related development efforts.

The Company includes revenue related to granted technology licenses as part of “Net sales.” Historically, revenue from these arrangements has not been significant though it is part of our recurring ordinary business. In the third quarter of fiscal year 2013, the Company entered into a single licensing arrangement that resulted in the recognition of $7.5 million of revenue.

The Company defers revenue recognition on shipment of products to certain customers, principally distributors, under agreements which provide for limited pricing credits or return privileges, until these products are sold through to end-users or the return privileges lapse. For sales subject to certain pricing credits or return privileges, the amount of future pricing credits or inventory returns cannot be reasonably estimated given the relatively long period in which a particular product may be held by the customer. Therefore, the Company has concluded that sales to customers under these agreements are not fixed and determinable at the date of the sale and revenue recognition has been deferred. The Company estimates the deferred gross margin on these sales by applying an average gross profit margin to the actual gross sales. The average gross profit margin is calculated for each category of material using standard costs which is expected to approximate actual costs at the date of sale. The deferred gross margin does not include any adjustments for sales returns. The estimated deferred gross margins on these sales, where there are no outstanding receivables, are recorded on the Unaudited Consolidated Condensed Balance Sheets under the heading of “Deferred revenue.”

The Company records a provision for estimated sales returns in the same period as the related revenues are recorded. The Company bases these estimates on historical sales returns and other known factors. Actual returns could be different from Company estimates and current provisions for sales returns and allowances, resulting in future charges to earnings.

Share-based Compensation, Option and Incentive Plans

Share-based Payment Arrangements

The Company has various equity award plans that provide for granting stock-based awards to employees and non-employee directors of the Company. The plans provide for the granting of several available forms of stock compensation. As of October 28, 2012, the Company has granted options and restricted stock under the plans and has also issued some stock-based compensation outside of the plans, including options and restricted stock issued as inducements to join the Company.

Grant Date Fair Values and Underlying Assumptions; Contractual Terms

The Company uses the Black-Scholes pricing model to value options. For awards classified as equity, stock-based compensation cost is measured at grant date, based on the fair value of the award, and is recognized as an expense over the employee’s or director’s requisite service period. For awards classified as liabilities, stock-based compensation cost is measured at fair value at the end of each reporting date until the date of settlement, and is recognized as an expense over the employee’s or director’s requisite service period. Expected volatilities are based on historical volatility using daily and monthly stock price observations.

Investments

Investments that have original maturities of three months or less are accounted for as cash equivalents. This includes money market funds, time deposits and U.S. government obligations. Temporary and long-term investments consist of government, bank and corporate obligations, and bank time deposits with original maturity dates in excess of three months. Temporary investments have original maturities in excess of three months, but mature within twelve months of the balance sheet date. Long-term investments have original maturities in excess of twelve months. The Company determines the cost of securities sold based on the specific identification method. Realized gains or losses are reported in “Interest income and other expense, net” on the Unaudited Consolidated Condensed Statements of Income.

The Company classifies its investments as “available for sale” because it may sell some securities prior to maturity. The Company’s investments are subject to market risk, primarily interest rate and credit risks. The Company’s investments are managed by a limited number of outside professional managers that operate within investment guidelines set by the Company. These guidelines include specified permissible investments, minimum credit quality ratings and maximum average duration restrictions and are intended to limit market risk by restricting the Company’s investments to high quality debt instruments with relatively short-term maturities.

Fair Value of Financial Instruments

When determining the fair value measurements for assets and liabilities required or permitted to be recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance. The Company uses the following three levels of inputs in determining the fair value of the Company’s assets and liabilities, focusing on the most observable inputs when available:

Level 1 - Quoted prices in active markets for identical assets or liabilities.

Level 2 - Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets with insufficient volume or infrequent transactions (less active markets); or model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 - Unobservable inputs to the valuation methodology that is significant to the measurement of fair value of assets or liabilities.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level in the fair value hierarchy within which the fair value measurement is disclosed is determined based on the lowest level input that is significant to the fair value measurement.

Goodwill and Intangible Assets, Goodwill

Goodwill is not amortized, but is tested for impairment using a two-step method on an annual basis and whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The recoverability of goodwill is measured at the reporting unit level by comparing the reporting unit’s carrying amount, including goodwill, to the fair market value of the reporting unit.

The fair value of goodwill is tested for impairment on a non-recurring basis in the accompanying Unaudited Consolidated Condensed Financial Statements using Level 3 inputs.

Goodwill and Intangible Assets, Intangible Assets

Purchased intangibles are amortized on a straight-line basis over their estimated useful lives. In-process research and development is recorded at fair value as of the date of acquisition as an indefinite-lived intangible asset until the completion or abandonment of the associated research and development efforts or impairment. Upon completion of development, acquired in-process research and development assets are transferred to finite-lived assets and amortized over their useful lives.

Goodwill and Intangible Assets, Intangible Assets, Indefinite-Lived

The Company reviews indefinite-lived intangible assets for impairment annually or whenever events or changes in circumstances indicate the carrying value may not be recoverable. Recoverability of indefinite-lived intangible assets is measured by comparing the carrying amount of the asset to the future discounted cash flows the asset is expected to generate. Acquired in-process research and development will be tested for impairment on a non-recurring basis in the accompanying consolidated financial statements using Level 3 inputs.