wanted: a smart / intelligent / call it what you bloody like mosfet - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 04:07:31 pm
content: I'm looking for one of those mosfets that has built in short circuit protection ect, fanell and RS as usual haven't a clue what I want because they employ people who havent a clue about what they are selling to categorise stuff and even google struggle to help.Ideally a 100V min mosfet that will protect at about 10A (I have offered a supply of up to 7A of current).

author: 2N3055
author_rank: Super Contributor
timestamp: February 11, 2017, 04:19:17 pm
content: I know about ON-semi and Infineon making those..ON-semi has different types, and Infineon has low side and high side mosfet based switches with protection...

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 04:20:31 pm
content: yes I just found the infinion page by copying the heading off a highside datasheet I had and then chossing low side.

author: Benta
author_rank: Super Contributor
timestamp: February 11, 2017, 04:40:20 pm
content: Infineon calls them PROFET. Be aware that they are rather slow.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 11, 2017, 05:06:03 pm
content: 100V * 10A = 1kW. That's an awfully generous protection mechanism...Are you sure you don't want something a little smarter, like a hot-swap controller (LM5069, etc.)?Even these only come up to 80V or so, and don't have enough gate drive and protection to handle more than about 10A. They're also kind of upside-down (high side switch!), but maybe you can turn that into a feature.Tim

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 06:11:09 pm
content: Well it's a 24V system but I need a VDS of 100V for some protection. I'm not promising anyone that it is fool proof but it would be nice to survive the odd breif short.Sent from my phone so mind the autocorrect.

author: max_torque
author_rank: Super Contributor
timestamp: February 11, 2017, 07:01:04 pm
content: Use a nice big TVS to clamp the supply to avoid having to have such a high Vds on your Fet?If you're FET can survive say 60v, then you can chose a TVS that has a nominal start of conduction at say 38V ish, which should clamp pretty much most transients to less than around 55V

author: james_s
author_rank: Super Contributor
timestamp: February 11, 2017, 07:06:36 pm
content: Even just thermal protection would be great. I've considered trying one of those protected mosfets in my Roomba robotic vacuum. I've had to replace the mosfet that drives the brush deck motor numerous times because the motor gets worn or the brushes get clogged up, draws excessive current and the mosfet experiences thermal runaway and shorts.

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 07:06:52 pm
content: yes well ball park I was looking 100V, first you need to stay above potential safe auto voltages that on a 24V nominal can real 30V (or I like to assume that for safety margin), then you need to pick a TVS that uless it is a big fat one can have a maximum clamping voltage well above that you would think so you end up with a 60V FET only 5V above your 55V being marginal. But yea basically I just want the facility to drive some sort of solenoid but having offered to do so not have them blow it up instantly like a regular mosfet and blame me. Or it's just bang a polyfuse in after a standard mosfet in case someone gets hand fisted.

author: halexa
author_rank: Regular Contributor
timestamp: February 11, 2017, 07:25:23 pm
content: Hi,ST.com make some that I used in automotive application were you want current sense and short circuit protection.http://www.st.com/content/st_com/en/products/automotive-analog-power-ics/high-and-low-side-drivers-switches.html

author: tpowell1830
author_rank: Frequent Contributor
timestamp: February 11, 2017, 08:04:08 pm
content: Quote from: Simon on February 11, 2017, 04:07:31 pmDo you mean like this one?http://www.mskennedy.com/sites/default/files/4205rh.pdf

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 08:07:35 pm
content: not really, that is an unprotected Hbridge, it does not even link the high and low sides together that go together.

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 08:16:43 pm
content: This one looks good:http://uk.farnell.com/stmicroelectronics/vnp10n07-e/mosfet-omnifet-70v-10a-to-220/dp/1739423?ost=VNP10N07&selectedCategoryId=&categoryNameResp=All%2BCategories&searchView=table&iscrfnonsku=false

author: tpowell1830
author_rank: Frequent Contributor
timestamp: February 11, 2017, 08:27:45 pm
content: Quote from: Simon on February 11, 2017, 08:16:43 pmSo how does the monitoring work? What are they calling the input pin?I copied the description here.The VNP10N07-E is a monolithic device fully auto protected Power MOSFET with ESD protection. The VNP10N07 is a monolithic device made using STMicroelectronics VIPower technology, intended for replacement of standard power MOSFETS in DC to 50kHz applications. Built-in thermal shut-down, linear current limitation and overvoltage clamp protect the chip in harsh environments. Fault feedback can be detected by monitoring the voltage at the input pin.Thermal shutdownIntegrated clampDiagnostic feedback through input pinLow current drawn from input pin

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 08:31:02 pm
content: It has a regular gate but an internal monitoring circuit will pull the gate low to limit the current or shut it off if it goes over temperature

author: tpowell1830
author_rank: Frequent Contributor
timestamp: February 11, 2017, 08:54:46 pm
content: Ok, they are $2 at Mouser. Atached pdf specs.

author: Simon
author_rank: Unknown
timestamp: February 11, 2017, 09:22:10 pm
content: Yes I read it, the $2 I guess is about the £1.56 Farnell want. Nice to know they are readily available.