Editing 555 timer IC (section)

== History ==
[[File:Die of the first 555 chip.jpg|thumb|Silicon die of the first 555 chip (1971)]]
[[File:NXP-7555-HD.jpg|thumb|Die of a CMOS NXP ICM7555 chip]]
The timer IC was designed in 1971 by [[Hans Camenzind]] under contract to [[Signetics]].<ref name="EEtimes_20120815"/>  In 1968, he was hired by Signetics to develop a [[phase-locked loop]] (PLL) IC.  He designed an oscillator for PLLs such that the frequency did not depend on the power supply voltage or temperature.  Signetics subsequently laid off half of its employees due to the [[Recession of 1969–70|1970 recession]], and development on the PLL was thus frozen.<ref name="Birth">{{Cite journal|last=Carmenzind|first=Hans|translator-last=三宅|translator-first=和司|year=2010|title=タイマIC 555 誕生秘話|trans-title=The birth of the 555 timer IC|journal=トランジスタ技術 (Transistor Technology)|language=ja|publisher=CQ出版|volume=47|issue=12|pages=73, 74|issn=0040-9413}}</ref>  Camenzind proposed the development of a universal circuit based on the oscillator for PLLs and asked that he develop it alone, borrowing equipment from Signetics instead of having his pay cut in half. Camenzind's idea was originally rejected, since other engineers argued the product could be built from existing parts sold by the company; however, the marketing manager approved the idea.<ref>{{Cite journal |first=Brian |last=Santo|url=https://spectrum.ieee.org/25-microchips-that-shook-the-world|title = 25 Microchips That Shook the World|date = May 2009 |journal=IEEE Spectrum|volume=46|issue=5|pages=34–43|doi=10.1109/MSPEC.2009.4907384|s2cid=20539726|url-access=subscription}}</ref>

The first design for the 555 was reviewed in the summer of 1971.<ref name="Redesigning" /> After this design was tested and found to be without errors, Camenzind got the idea of using a direct resistance instead of a constant current source, finding that it worked satisfactorily.<ref name="Redesigning" /> The design change decreased the required 9 external pins to 8, so the IC could be fit in an 8-pin package instead of a 14-pin package.<ref name="Redesigning" /> This revised version passed a second design review, and the prototypes were completed in October 1971 as the NE555V (plastic [[Dual in-line package|DIP]]) and SE555T (metal [[TO-5]]).<ref name="semiconductormuseum-interview">{{cite web |url=http://www.semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Index.htm |last=Ward |first=Jack |date=2004 |title=The 555 Timer IC – An Interview with Hans Camenzind |publisher=The Semiconductor Museum |access-date=2010-04-05}}</ref>  The 9-pin version had already been released by another company founded by an engineer who had attended the first review and had retired from Signetics; that firm withdrew its version soon after the 555 was released. The 555 timer was manufactured by 12 companies in 1972, and it became a best-selling product.<ref name="Birth"/>

The 555 found many applications beyond timers. Camenzind noted in 1997 that "nine out of 10 of its applications were in areas and ways I had never contemplated. For months I was inundated by phone calls from engineers who had new ideas for using the device."<ref name="Redesigning" />

=== Name ===
Several books report the name "555" timer IC derived from the three 5 kΩ resistors inside the chip.<ref>{{Cite book|last1=Scherz|first1=Paul|url=https://books.google.com/books?id=lhSCCwAAQBAJ|title=Practical Electronics for Inventors |edition=4th |last2=Monk|first2=Simon|date=2016 |publisher=McGraw Hill |isbn=978-1-259-58755-9|pages=687|quote=The 555 gets its name from the three 5-kW +VCC R1 discharging path 555 R 2 C 6 resistors shown in the block diagram. These resistors act as a three-step voltage.}}</ref><ref>{{Cite book|last=Kleitz|first=William|title=Digital electronics : a practical approach|publisher=Prentice Hall|year=1990|isbn=0-13-211657-X|edition=2nd|pages=401|oclc=20218185|quote=The 555 got its name from the three 5-kOhm resistors}}</ref><ref>{{Cite book|last=Simpson|first=Colin D. |title=Industrial electronics|publisher=Prentice Hall|year=1996|isbn=0-02-410622-4|pages=357|oclc=33014077|quote=The reference voltage for the comparators is established by a voltage divider consisting of three 5 - k2 resistors, which is where the name 555 is derived}}</ref> However, in a recorded interview with an online transistor museum curator,<ref>{{Cite journal |first=Harry |last=GoldStein |date=March 3, 2003|title=The Irresistible Transistor|url=https://spectrum.ieee.org/the-irresistible-transistor|access-date=2020-08-29|journal=IEEE Spectrum|volume=40 |issue=3 |pages=42–47 |doi=10.1109/MSPEC.2003.1184435 |url-access=subscription }}</ref> Hans Camenzind  said "It was just arbitrarily chosen. It was Art Fury (marketing manager) who thought the circuit was gonna sell big who picked the name '555' timer IC."<ref>{{Cite web|title=Oral History Hans Camenzind Historic 555 IC Page2|url=http://www.semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Page2.htm|access-date=2020-08-28|publisher=The Semiconductor Museum}}</ref>