| Document and Entity Information | Jun. 02, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jun. 2, 2021 |
| Entity Registrant Name | SEMTECH CORP |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-06395 |
| Entity Tax Identification Number | 95-2119684 |
| Entity Address, Address Line One | 200 Flynn Road |
| Entity Address, City or Town | Camarillo |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 93012-8790 |
| City Area Code | 805 |
| Local Phone Number | 498-2111 |
| Entity Information, Former Legal or Registered Name | Not applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000088941 |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | SMTC |
| Security Exchange Name | NASDAQ |
