What kind of fuse is this? - Page 1
Forum section: electronics / projects

author: DaGlitch
author_rank: Contributor
timestamp: September 12, 2014, 07:54:44 pm
content: Was just looking through a schematic and saw this fuse symbol that I've never seen before. Anyone have an idea of what this is?

author: ElektroQuark
author_rank: Unknown
timestamp: September 12, 2014, 07:57:43 pm
content: It looks like that when the fuse dies an output is enable.

author: DaGlitch
author_rank: Contributor
timestamp: September 12, 2014, 08:20:40 pm
content: Yea the bottom output as shown goes to a fail-safe protection input pin. I have just never seen that symbol used before and was wondering if there was a fuse that actually had 3 pins like that. I was thinking they just combined some things into one symbol, but couldn't find any reference making me think that.

author: bktemp
author_rank: Super Contributor
timestamp: September 12, 2014, 08:27:36 pm
content: Those fuses are often used as battery protectors for lithium batteries: When the circuit detects an overvoltage from the charger it pulls the centre pin to ground until the fuse blows and disconnects the connection to the battery.Here is a datasheet for such a device:http://battery.newlist.ru/images2/Fuse.pdf

author: zapta
author_rank: Super Contributor
timestamp: September 12, 2014, 08:34:27 pm
content: It's called a chemical fuse. You can force it to burn with a signal. Hard to find. You may find the in notebook battery packs and others.

author: DaGlitch
author_rank: Contributor
timestamp: September 12, 2014, 08:35:49 pm
content: That would be the answer to my question. Thank you very much guys!

author: DaGlitch
author_rank: Contributor
timestamp: September 12, 2014, 09:27:33 pm
content: Been thinking of an alternative way to achieve a similar effect, since those are pretty hard to find parts. Ideas?

author: zapta
author_rank: Super Contributor
timestamp: September 12, 2014, 09:40:55 pm
content: Quote from: DaGlitch on September 12, 2014, 09:27:33 pmOne way is to actually cause high current through the fuse, for example by triggering a transistor or an SCR, assuming your power source has sufficient current capability. Another is to write a bit in nonvoletaile memory that will cause a series transistor never to turn on again.Do you plan to use it for a battery pack? Look at the bq20z45-R1 datasheet for example. It has three levels of protection, two series transistors and one chemical fuse (triggered by the SAFE signal).

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 12, 2014, 10:03:41 pm
content: Quote from: DaGlitch on September 12, 2014, 09:27:33 pmhttp://www.sii-ic.com/en/semicon/products/power-management-ic/lithium-ion-battery-protection-ic/

author: DaGlitch
author_rank: Contributor
timestamp: September 12, 2014, 10:22:36 pm
content: Yea it will be used in a battery pack. Appreciate the feedback. Just thinking of design alternatives

author: PChi
author_rank: Frequent Contributor
timestamp: September 13, 2014, 12:06:49 pm
content: The closest to that symbol that I have seen are thermal fuses with integral resistors.http://www.atcsemitec.co.uk/pdfdocs/d6x-thermal-fuses.pdf