Oct 30 (Reuters) - Monolithic Power Systems said it would buy back up to $640 million-worth company shares and reported largely in-line results on Monday, sending its stock up 8% in trading after the bell.

Kirkland, Washington-based Monolithic, which sells power circuits and other semiconductor products, is seeing demand scale as enterprises upgrade their cloud and network infrastructure to support new AI functionality and the growing Internet user-base.

The new buyback plan will be valid through October 2026. Monolithic Power's shares have gained 14.3% compared with the 22.2% rise in technology-heavy Nasdaq Composite year to date. The company had $1 billion in cash and equivalents as of September.

In the current quarter ending Dec. 31, the company sees revenue between $442 million and $462 million. The midpoint of the range came in slightly below the $451.7 million estimate, according to LSEG data.

Revenue decreased 4% to $474.9 million in the most-recent quarter ended Sept. 30, compared with analysts' consensus estimate of $474.1 million.

It earned $3.08 per share, slightly higher than the estimate of $3.07.

Sales to storage and computing customers, the largest end-market for Monolithic Power, grew 15% to $129.5 million. Its second-largest revenue line, enterprise data, jumped over 30% to $98.9 million. (Reporting by Yuvraj Malik in Bengaluru; Editing by Krishna Chandra Eluri)