Franklin Antonio, the UC San Diego graduate who co-founded chipmaker Qualcomm, helping fan the growth of everything from cellphones to social media to wearable medical devices, has died, the company said late Friday.

Qualcomm did not say when, where or why the 69-year-old Antonio died.

“I’m very sad to share that Franklin Antonio, EVP & Chief Scientist, Emeritus, has passed away,” Qualcomm CEO Cristiano Amon told workers in an internal message.

“As employee #7, Franklin was one of Qualcomm’s original founders and our longest-serving employee,” the message read. “He was personally involved in so many of Qualcomm’s early technology breakthroughs and, simply put, we would not be the company we are today without his contributions.”

Antonio’s passing also drew a heartfelt response from Irwin Jacobs of La Jolla, the main force behind the founding of Qualcomm.

“This is really tragic,” Jacobs told the Union-Tribune. “He was a student of mine at UCSD, one of the best undergraduates that I have ever had.

“He then worked with me at Linkabit and at Qualcomm. He was a key figure in the success of both companies.”

Jacobs added that Antonio “was a different kind of person. He didn’t always respond to foolish remarks gently. But he was very sharp and helpful. I often used him as an example of the kind of person you need in a company.”

Antonio also was one of San Diego’s well-known philanthropists. UCSD is preparing to open a $180 million engineering center that was seeded with an initial $30 million gift from him. He also donated to Father Joe’s Villages, and the lunch program was renamed in his honor — the Franklin Antonio Public Lunch Program — several years ago.

Major donors usually talk in broad strokes. But Antonio took a very personal approach in 2019 when he donated $30 million to UCSD for the new engineering building.

“As UCSD has grown, I worry about the undergraduate experience,” Antonio told the Union-Tribune “I see this sea of undergraduates and I can’t imagine that they all get the faculty access that I wish they would have.

“The interaction between the students and the faculty is the reason we have the university. If you didn’t need that, you could all just watch online courses.”

Albert Pisano, dean of UCSD’s Jacobs School of Engineering, said, “I will miss Franklin greatly. He was a true visionary and a brilliant engineer.

“His generosity and collaboration were remarkable. Franklin and I connected on a deep understanding of the importance of creating an engineering building that puts the student experience first by baking the circulation of people and ideas into the design of the building.”

Pisano said he feels a responsibility to carry forward the mission that Antonio wanted.

“If you look at Franklin’s career, he was a prolific inventor with hundreds of patents,” said Pisano, who aims to make the building “a giant, productive machine to create all these other patents and inventions and innovations.

“It’s so tragic. We feel we’ve lost a very important partner,” he continued. “But with that loss, we are resolved that we will do everything possible to carry forward the legacy that he wanted us to carry for him. We are determined to be successful in that.”

Antonio graduated from UCSD in 1974 with a bachelor’s degree in applied physics and information science. He worked at Linkabit for 12 years before joining Jacobs, Andrew Viterbi and four others — Adelia Coffman, Klein Gilhousen, Harvey White and Andrew Cohen — to found Qualcomm in 1985. Gilhousen died in 2016.

Antonio fostered the growth of Qualcomm’s engineering department and served as project engineer for the company’s OmniTRACS satellite communication system. Antonio also contributed to Qualcomm’s code division multiple access (CDMA) technology and Globalstar low-Earth-orbit satellite system.

Phil Karn worked with Antonio for more than two decades and said he’s the reason he came to San Diego. Before Antonio recruited him to work for Qualcomm in the 1990s, they forged a cross-country friendship through their love of HAM radios.

Karn retired from Qualcomm in 2011 and said that Antonio was easily one of the most brilliant people he’d ever worked for but noted he was tough.

Karn recalled an impossibly difficult math question that Antonio would pose to new engineers during job interviews that became known as the “Kobayashi Maru” — named after the no-win training exercise in Star Trek. He explained that the point wasn’t to see if someone could solve it, but so Antonio could see how they tackled the problem.

Another close friend of Antonio’s was Matt Grob, who started at Qualcomm the same day as Karn. He worked at Qualcomm for 27 years and though Grob didn’t directly report to Antonio, he always valued his guidance. He credited Antonio with pushing for innovation at Qualcomm as he was known to have high expectations.

“He would challenge you,” Grob said. “We were grateful to know him and … benefit from his knowledge that he would share. He was always open to share his opinion.

“A lot of the engineering culture of Qualcomm, which is a great company, was influenced by Franklin,” Grob said. “I mean, he would see things as they are, he would dig in and get to the heart of the matter. And then want to understand why this choice of software was better than that choice of software. This algorithm was better than that algorithm.”

Outside of work, Karn said Antonio was a very private person and he did not have family in the San Diego area. He was an only child who grew up in Clovis, a California town known for its farming. A few years ago, the town also recognized Antonio for being one of its most famous past residents.

In San Diego, Antonio’s name will live on through the new engineering building at UCSD. Karn and his friends joked that the perfect plaque to put outside the building to pay tribute to Antonio would be the challenging Kobayashi Maru math equation.