Onsemi Is Buying Synaptics for $7 Billion in Stock. Its Own Investors Marked It Down 6%.

Onsemi agreed on Thursday to buy Synaptics in an all-stock deal worth about $7 billion, the largest acquisition the company has ever made. Then its own shareholders marked the stock down roughly 6% in after-hours trading. Synaptics shares went the other way, up about 13%. That split tells you most of what you need to know about who is paying and who is getting paid.

This is the deal: onsemi, the Scottsdale, Arizona chipmaker known for power and analog parts, is handing Synaptics holders 1.350 onsemi shares for every Synaptics share. That works out to about a 19% premium, but measured against the 10-day volume-weighted average price of both stocks, not against Wednesday's close. When the dust settles, Synaptics shareholders are expected to own about 12% of the combined company. Synaptics becomes a wholly owned onsemi subsidiary and gets delisted from Nasdaq. The companies expect to close in the middle of 2027, which is a long time to wait and a long time for regulators to look.

What onsemi is actually buying

Synaptics is the company behind a lot of hardware you have touched without thinking about it: touchpad and touchscreen controllers, fingerprint sensors, display drivers. That was the old business. The part onsemi cares about is the newer one. Synaptics has been pushing into edge AI silicon, the Astra line of system-on-chips meant to run models on the device instead of in a data center, plus wireless connectivity parts including Wi-Fi 7.

The numbers say the pivot is real. For its fiscal year ended June 28, 2025, Synaptics reported $1.074 billion in revenue, up 12%. The standout was Core IoT, which grew 53% year over year and now makes up roughly a quarter of the company. So onsemi is not buying a dying touch-sensor vendor. It is buying sensing and connectivity parts that sit at the edge, next to the power and analog chips onsemi already sells.

The buzzword, translated

Onsemi is selling this under the banner of "physical AI." Translated once: AI that runs in machines and devices that move and sense in the real world (cars, factories, appliances) rather than AI that runs on servers answering chat prompts. CEO Hassane El-Khoury laid out the pitch in the company's own words:

As artificial intelligence moves beyond the cloud and into the physical world, including automotive and industrial, the next phase of innovation will depend on systems that can sense, decide, act and adapt in real time. This shift towards Physical AI will require Power, Sense, Connected Compute and Control to work together seamlessly.

Strip the capital letters off the four pillars and the logic is sound. A self-driving feature or a factory robot needs something to power it, something to sense its surroundings, something to do compute locally, and something to control the result. Onsemi is strong on power and control. Synaptics brings the sensing and the connected compute. On a whiteboard, the pieces fit. The skepticism is not about whether the parts complement each other. It is about the price and the math attached to it.

The numbers worth questioning

Onsemi says the deal adds $30 billion to its total addressable market, lifting it to $243 billion by 2030. Keep two things straight here. Total addressable market is not revenue, and a number ending in 2030 is a forecast, not a result. Every chip company draws a giant TAM circle around its product category and points at it during acquisitions. It is the slide that justifies the premium. Treat the $243 billion the way you would treat any five-year projection from a party with a reason to make it large.

The harder numbers are these: onsemi expects the deal to add to non-GAAP earnings per share within 18 months of closing, and it is targeting $200 million in annual synergies. "Non-GAAP" and "synergies" are both worth a raised eyebrow. Non-GAAP earnings strip out the cost of the stock onsemi is printing to pay for this. And $200 million in synergies on a $7 billion deal is the kind of round figure that shows up in the press release and gets revised later.

Why the buyer's stock fell

Here is the part that matters. When a company pays cash, the market judges the target. When a company pays entirely in its own stock, the market judges the acquirer, because existing shareholders are being diluted to fund the purchase. Onsemi down 6% and Synaptics up 13% is the market saying it likes the deal more for the seller than the buyer. That is common in all-stock acquisitions, and it is not by itself a verdict that the deal is bad. It is a signal that onsemi's investors are not yet convinced the $7 billion in new shares will earn their keep.

The strategic case is coherent. Onsemi wants to be the company that supplies the full bill of materials for intelligent edge devices, and Synaptics fills real gaps. Whether that is worth diluting your shareholders by paying a premium in stock that the same shareholders just discounted is the question onsemi has until mid-2027 to answer.