Document And Entity Information	6 Months Ended
	Jul. 29, 2012	Aug. 31, 2012
Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Jul. 29, 2012
Amendment Flag	false
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2
Entity Registrant Name	SEMTECH CORP
Entity Central Index Key	0000088941
Current Fiscal Year End Date	--01-27
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		65,938,219