Jan 21, 2014

Guru #5, Tom Redfern

Of the five “gurus” in the early Linear Technology advertisement, Tom Redfern was the one I knew best from my days at National Semiconductor. But I didn’t know him as a “guru” – just as an incredibly smart, effervescent and really nice guy – always with a big smile. So I had to ask him how he ended up on that particular advertisement.


Tom Redfern did his graduate work at Stanford University in Control Theory and by chance did a lot of work with A/Ds and D/As. After his masters degree, he went to work at Garrett Corporation (aerospace) and managed a circuit design group and also did work with A/Ds and D/As. There he worked on an all-digital computer for the F14 Tomcat. “While at Garrett I used military grade µA709's in a jet engine fuel control application. We were on allocation because Fairchild could not supply the demand and we paid $75 each for them. Can you imagine! Fairchild was printing money in those days (circa 1967),” per Tom. The contract, for the F14 computer, was awarded to American Micro-Systems (AMI) for the custom MOS chip set. He became enamored with MOS semiconductors and joined AMI as a field applications engineer in Southern California. At the time the only two companies capable of manufacturing reliable MOS devices were AMI and General Instruments. Only metal gate P-MOS was available in those days. No N-MOS and consequently no CMOS.

Garrett started a new MOS company, Garrett Micro-Circuit Corp. (GMCC) in Rancho Bernardo, CA (San Diego area). Tom joined as the Applications Manager. Originally AMI had more business than they could handle and GMCC would get the business they could not address. By the time GMCC got their factory up and running, business had slowed and AMI did not need this extra capacity. There were lawsuits and bad feelings and eventually Garrett recovered their investment by selling the fab to Burroughs. (Garrett is now Honeywell International.) When GMCC was sold to the Burroughs Corp, Tom left for National Semiconductor (1971) as a Field Applications Engineer covering Orange County to San Diego. After one year he moved to the headquarters as the MOS Product Marketing Manager. He had various jobs at National ending up working as the Data Acquisition Design Manager. At the time, there were three analog groups under Vice President Bob Swanson at National: ALIC (Advanced Linear Integrated Circuits) headed by Bob Dobkin, CLIC (Consumer Linear Integrated Circuits) headed by Tim Isbell, and SLIC (Standard Linear Integrated Circuits) headed by Jim Solomon. Tom worked for Solomon. Along the way, he amassed several fundamental patents for MOS circuits; many focused on A/D's.

Tom noted that while working for Jim Solomon, he was given the task of designing a twelve bit A/D. “Consensus was, at the time, this required 15 volt supplies and bipolar circuit technology. I convinced Jim that I could do it at 5V in CMOS. The rest is history and that pretty much established my ‘guru’ status in CMOS.”

In 1981, Swanson and Dobkin left National to start up Linear Technology Corp. Around then Tom left and joined Intersil which was very strong in CMOS. Tom worked for Dave Fullagar, who reported to Jack Gifford. Immediately, Dobby lured him over to Linear.

“I was employee #22, I think. I had left National to join Intersil. After a week there I got a call from Dobkin about joining LTC. I said ‘I never thought of that because I thought you guys were strictly focused on bipolar.’ He said investors were insisting LTC do CMOS as well and they needed someone to start that effort. I signed up and we worked in rented space on Bernardo Ave in Mountain View (by Central Expressway and 237). Who was there that I remember: Bob Swanson, Bob Dobkin, George Erdi, Carl Nelson, Brent Welling, Brian Hollins, Wadie Khaddar and Una Brown.” (Bob Widlar was also there, but living in Mexico.)
“I worked with Wadie to define the first CMOS process. It turns out this had a very positive effect on LTC's bipolar process. LTC could not afford to put two fabs in place so everything was processed in the same line. Because MOS is very sensitive to surface contamination the whole process had to meet MOS requirements. This meant the bipolar circuits had very good noise performance.”
 Tom did a significant amount of work on the CMOS process at Linear Technology:
“One of my many jobs at National was I headed up a group responsible for process characterization and device modeling. Device models were, of course, used with the circuit simulation programs. This experience along with my education gave me a very solid background in device physics. This was of great value as a designer and helped define the process we finally came up with. My philosophy was to define and characterize the process thoroughly. Test chips on every wafer allowed us to measure and control critical process parameters. If a design did not work right, and the process met its specifications, then it was a design problem. The process guys loved this because they only had to have one process and they just needed to keep it in control."
As I recall Wadie was the process engineer/manager I worked with.”
At one point MOS Design, Mask Design, CAD and Applications reported directly to Tom. He noted that Linear Technology has always been very design centric. He said the operator had a list of design engineers and which products they'd done. If a customer asked to speak with a design engineer about their product they were transferred to that designer.
“The ‘guru’ thing, in my opinion, is a bunch of hype. There are a lot of really bright people in the world who are just as smart and creative as any of us.”
Ultimately, Tom left in 1989 and eventually moved back to National Semiconductor.  That’s where I met him, around 1993 perhaps.

In 1997, Tom was awarded National Semiconductor Corporation's first Fellow Award, given to the technologist who has consistently shown outstanding contributions. The Fellow was National's highest technical position. In the announcement, Tom was credited for eleven patents, eight while working at National, and he won National's "Most Outstanding Patent of the Year" award in 1979 for his charge balance techniques used in the manufacture of analog to digital converters. In 1987, he was recognized by Electronic Products magazine's "Product of the Year" award for his one-chip data acquisition system.

An article in the April 13, 1995 issue of Electronic Design News (EDN), "On the Shoulders of Giants," recognized Tom Redfern as a genius in his field. "When we contemplate powerful desktop computers..., we tend to think of the geniuses who made such wonders possible. In information theory, great thinkers such as Von Neumann and Wiener come to mind. In linear technology, we have Dobkin, Philbrick, Redfern, and Widlar."

Whether Tom accepts the mantle of “guru” or “genius”, he’s in good company.


No comments:

Post a Comment