Any insight for Automotive Sensor Inputs/ Front-End Protection.
in [Design]
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From: Fred Bartoli on 27 Apr 2010 05:14 Joerg a �crit : > Jim Thompson wrote: >> On Mon, 26 Apr 2010 16:57:30 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jim Thompson wrote: >>>> On Mon, 26 Apr 2010 16:18:05 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> Jamie wrote: >>>>>> Johnny5 wrote: >>>>>>> I was curious if anyone had any insight into protecting an Opto- >>>>>>> isolator LED input from load dump, Jumpstarts, and many of the other >>>>>>> signals in the auto environment. FETS,CLIPPERS,Clamps? >>>>>>> Thank you in advance, >>>>>>> It is an open drain SSR. >>>>>> TVS diodes. Transorbs is another name for them. >>>>>> >>>>> Also Transzorb. And ST calls them Transil. It's trade names, like >>>>> Kleenex or Kim Wipes. >>>>> >>>>> [...] >>>> No canned answers. It depends on the circuitry. >>>> >>> Sure it does. But it ain't rocket science. There must be a resistor, >>> then a TVS to GND, then another resistor, then LED to GND. The latter >>> resistor is sometimes part of the SSR already. >>> >>> Hey, anyone else have issues with a Digikey order today? I was on the >>> phone with their IT for over an hour, they were becoming frustrated >>> as well, still no answer what's wrong. Had to order at Mouser now. >> >> Who the frick needs a TVS? >> > > Entirely depends on the SSR. If it's a 12V input version and abs max sez > you'd be gitten a *PHUT* sound at 30V you better put somethin' in there > :-) > Ah, I knew you were going to that :-) -- Thanks, Fred.
From: John Devereux on 28 Apr 2010 13:09 Johnny5 <dirtylogicdesigns(a)gmail.com> writes: > On Apr 26, 6:35 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- > Web-Site.com> wrote: >> On Mon, 26 Apr 2010 16:18:05 -0700, Joerg <inva...(a)invalid.invalid> >> wrote: >> >> >Jamie wrote: >> >> Johnny5 wrote: >> >>> I was curious if anyone had any insight into protecting an Opto- >> >>> isolator LED input from load dump, Jumpstarts, and many of the other >> >>> signals in the auto environment. FETS,CLIPPERS,Clamps? >> >>> Thank you in advance, >> >>> It is an open drain SSR. >> >> TVS diodes. Transorbs is another name for them. >> >> >Also Transzorb. And ST calls them Transil. It's trade names, like >> >Kleenex or Kim Wipes. >> >> >[...] >> >> No canned answers. It depends on the circuitry. >> [...] > Thank you all for the input, a little more on the circuit . Sensors > are pressure switches/Temp that are connected to Vbatt. Pressure High= > relay that switches Vbatt on/off. No current Limit. So I was thinking > it would be best use opto. HSR312 SSR, Vr=7v, Vf=1.6V , control > current approx 2mA. > > > Automotive opto front end for Vbatt switched with no current limit > > Bav99/ TVS with a current limiter suffice? ? > polarity protection p channel fet as well? any choice on fet, dmos > only? > thks Do you actually need to do anything? LEDS will survive brief overcurrent just fine. If you size the LED resistor for 12V operation near the 2mA, you will have to get up to 100V or so to even get to its rated 25mA maximum. Any such pulses will be very brief, the LED won't mind. I would just use a series resistor and connect a signal diode in anti-parallel across the LED. -- John Devereux
From: Jim Thompson on 28 Apr 2010 13:18 On Wed, 28 Apr 2010 18:09:18 +0100, John Devereux <john(a)devereux.me.uk> wrote: >Johnny5 <dirtylogicdesigns(a)gmail.com> writes: > >> On Apr 26, 6:35�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >> Web-Site.com> wrote: >>> On Mon, 26 Apr 2010 16:18:05 -0700, Joerg <inva...(a)invalid.invalid> >>> wrote: >>> >>> >Jamie wrote: >>> >> Johnny5 wrote: >>> >>> I was curious if anyone had any insight into protecting an Opto- >>> >>> isolator LED input from load dump, Jumpstarts, and many of the other >>> >>> signals in the auto environment. FETS,CLIPPERS,Clamps? >>> >>> Thank you in advance, >>> >>> It is an open drain SSR. >>> >> TVS diodes. Transorbs is another name for them. >>> >>> >Also Transzorb. And ST calls them Transil. It's trade names, like >>> >Kleenex or Kim Wipes. >>> >>> >[...] >>> >>> No canned answers. �It depends on the circuitry. >>> > >[...] > >> Thank you all for the input, a little more on the circuit . Sensors >> are pressure switches/Temp that are connected to Vbatt. Pressure High= >> relay that switches Vbatt on/off. No current Limit. So I was thinking >> it would be best use opto. HSR312 SSR, Vr=7v, Vf=1.6V , control >> current approx 2mA. >> >> >> Automotive opto front end for Vbatt switched with no current limit >> >> Bav99/ TVS with a current limiter suffice? ? >> polarity protection p channel fet as well? any choice on fet, dmos >> only? >> thks > >Do you actually need to do anything? LEDS will survive brief overcurrent >just fine. If you size the LED resistor for 12V operation near the 2mA, >you will have to get up to 100V or so to even get to its rated 25mA >maximum. Any such pulses will be very brief, the LED won't mind. > >I would just use a series resistor and connect a signal diode in >anti-parallel across the LED. There you go! So many posters here want to make simple problems difficult... TVS's, etc :-] ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Joerg on 28 Apr 2010 14:33 Jim Thompson wrote: > On Wed, 28 Apr 2010 18:09:18 +0100, John Devereux > <john(a)devereux.me.uk> wrote: > >> Johnny5 <dirtylogicdesigns(a)gmail.com> writes: >> >>> On Apr 26, 6:35 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >>> Web-Site.com> wrote: >>>> On Mon, 26 Apr 2010 16:18:05 -0700, Joerg <inva...(a)invalid.invalid> >>>> wrote: >>>> >>>>> Jamie wrote: >>>>>> Johnny5 wrote: >>>>>>> I was curious if anyone had any insight into protecting an Opto- >>>>>>> isolator LED input from load dump, Jumpstarts, and many of the other >>>>>>> signals in the auto environment. FETS,CLIPPERS,Clamps? >>>>>>> Thank you in advance, >>>>>>> It is an open drain SSR. >>>>>> TVS diodes. Transorbs is another name for them. >>>>> Also Transzorb. And ST calls them Transil. It's trade names, like >>>>> Kleenex or Kim Wipes. >>>>> [...] >>>> No canned answers. It depends on the circuitry. >>>> >> [...] >> >>> Thank you all for the input, a little more on the circuit . Sensors >>> are pressure switches/Temp that are connected to Vbatt. Pressure High= >>> relay that switches Vbatt on/off. No current Limit. So I was thinking >>> it would be best use opto. HSR312 SSR, Vr=7v, Vf=1.6V , control >>> current approx 2mA. >>> >>> >>> Automotive opto front end for Vbatt switched with no current limit >>> >>> Bav99/ TVS with a current limiter suffice? ? >>> polarity protection p channel fet as well? any choice on fet, dmos >>> only? >>> thks >> Do you actually need to do anything? LEDS will survive brief overcurrent >> just fine. If you size the LED resistor for 12V operation near the 2mA, >> you will have to get up to 100V or so to even get to its rated 25mA >> maximum. Any such pulses will be very brief, the LED won't mind. >> >> I would just use a series resistor and connect a signal diode in >> anti-parallel across the LED. > > There you go! > > So many posters here want to make simple problems difficult... TVS's, > etc :-] > Those posters tend to design reliable electronics :-) Figure 1, for a dose of reality: http://www.automotivedesignline.com/howto/205101011 Usually an LED survives that. But sometimes, especially when dumps happen in rapid succession, it doesn't. I don't have too much experience with automotive stuff for passenger cars but I do with electronics for larger vehicles such as aircraft. There, a non-TVS design is most likely going to hit the fan before it ever sees its fuselage mounting spot. At the RTCA test lab. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 28 Apr 2010 18:04
On Wed, 28 Apr 2010 11:33:00 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Wed, 28 Apr 2010 18:09:18 +0100, John Devereux >> <john(a)devereux.me.uk> wrote: >> >>> Johnny5 <dirtylogicdesigns(a)gmail.com> writes: >>> >>>> On Apr 26, 6:35 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >>>> Web-Site.com> wrote: >>>>> On Mon, 26 Apr 2010 16:18:05 -0700, Joerg <inva...(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> Jamie wrote: >>>>>>> Johnny5 wrote: >>>>>>>> I was curious if anyone had any insight into protecting an Opto- >>>>>>>> isolator LED input from load dump, Jumpstarts, and many of the other >>>>>>>> signals in the auto environment. FETS,CLIPPERS,Clamps? >>>>>>>> Thank you in advance, >>>>>>>> It is an open drain SSR. >>>>>>> TVS diodes. Transorbs is another name for them. >>>>>> Also Transzorb. And ST calls them Transil. It's trade names, like >>>>>> Kleenex or Kim Wipes. >>>>>> [...] >>>>> No canned answers. It depends on the circuitry. >>>>> >>> [...] >>> >>>> Thank you all for the input, a little more on the circuit . Sensors >>>> are pressure switches/Temp that are connected to Vbatt. Pressure High= >>>> relay that switches Vbatt on/off. No current Limit. So I was thinking >>>> it would be best use opto. HSR312 SSR, Vr=7v, Vf=1.6V , control >>>> current approx 2mA. >>>> >>>> >>>> Automotive opto front end for Vbatt switched with no current limit >>>> >>>> Bav99/ TVS with a current limiter suffice? ? >>>> polarity protection p channel fet as well? any choice on fet, dmos >>>> only? >>>> thks >>> Do you actually need to do anything? LEDS will survive brief overcurrent >>> just fine. If you size the LED resistor for 12V operation near the 2mA, >>> you will have to get up to 100V or so to even get to its rated 25mA >>> maximum. Any such pulses will be very brief, the LED won't mind. >>> >>> I would just use a series resistor and connect a signal diode in >>> anti-parallel across the LED. >> >> There you go! >> >> So many posters here want to make simple problems difficult... TVS's, >> etc :-] >> > >Those posters tend to design reliable electronics :-) Nonsense! Find a single one of my chip designs that's ESD sensitive... including those I designed in the '60's. > >Figure 1, for a dose of reality: >http://www.automotivedesignline.com/howto/205101011 Learn to read. Particularly my automotive patents. Not a single TVS in sight. > >Usually an LED survives that. But sometimes, especially when dumps >happen in rapid succession, it doesn't. I don't have too much experience >with automotive stuff for passenger cars but I do with electronics for >larger vehicles such as aircraft. There, a non-TVS design is most likely >going to hit the fan before it ever sees its fuselage mounting spot. At >the RTCA test lab. Circuits should be designed from the outset to survive. After-the-fact patches, like TVS's, are for amateurs :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy |