The Docomo-backed mobile device semiconductor maker has now raised $50m in debt and equity.

US-based semiconductor producer Quantance has raised $6m in funding of a round that could increase to $9m, according to an SEC filing on Tuesday.

Quantance’s latest investors were not disclosed, but the company has now raised approximately $50m, including $12m from a series D round in April 2013 backed by Docomo Capital, the corporate venturing arm of telecommunications company Docomo, TD Fund, Granite Ventures and InterWest Partners.

The same investors earlier combined to invest $11m in Quantance, which focuses on the mobile device market, in 2008.