Organization And Basis Of Presentation (Policy)	3 Months Ended
Organization And Basis Of Presentation (Policy)	Apr. 29, 2012
Organization And Basis Of Presentation [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, although 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 first 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 accounting principles generally accepted in the United States 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.

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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+ Details

- Definition

Disclosure of accounting policy for determining an entity's fiscal year or other fiscal period. This disclosure may include identification of the fiscal period end-date, the length of the fiscal period, any reporting period lag between the entity and its subsidiaries, or equity investees. If a reporting lag exists, the closing date of the entity having a different period end is generally noted, along with an explanation of the necessity for using different closing dates. Any intervening events that materially affect the entity's financial position or results of operations are generally also disclosed.

+ References+ Details

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

+ References+ Details