1. Home
  2. Electronics Design
  3. Any insight for Automotive Sensor Inputs/ Front-End Protection.
  4. Page 2

Any insight for Automotive Sensor Inputs/ Front-End Protection.

The Romans? Man, you _are_ old :-)

Ok, then: The tougher category is 80V for 100msec, followed by 48V for one second. Three times at 10sec intervals. Depending on what it is the circuit can pause, but ideally it should just continue to work through these episodes. Throw in 600V spikes as well but they are brief and thus easy. So?

Remember, you've got 15 pennies to play with, no more. And if you use lots of parts then you are charged a pick-and-place tax.

One electronic board but not at liberty to tell.

Nothing, assuming big rigs don't count here. However, some of my 12V designs are allowed to be run on vehicles and on ships (and do so nicely).

I've got tons designs of intra-body stuff. But all this doesn't matter. You said using TVS is like making simple problems difficult so let's not deviate here. How do you solve the problem you snipped away, sans TVS, for less than 15c in parts?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg
Loading thread data ...

Broadband KU band communications system aboard the ISS.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Reply to
Michael A. Terrell

Yep.

I first encountered load dump around 1964. I'll not tell you how I solved it, I'll make you read my patents and see if you can discern how I did it... by clever circuit design... no TVS's... I don't even think they existed then :-)

Clever design, read my patents and learn from a (very old) master :-) ...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
Reply to
Jim Thompson

Hey, you are deviating now. How would you solve the problem I presented? "Spend the next two days reading through umpteen patents" ain't the answer. The answer would be a circuit sketch. So?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

YOUR problem, as a designer, is that you must use off-the-shelf stuff that is not designed to withstand abuse, and ADD stuff to it to make it survive.

MY problem, when designing a chip, is to make the circuit survive on its own, in the first place. Over the years I've become most clever at that skill :-)

MY '60's designs survive load dump. Wonder how ?:-) ...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
Reply to
Jim Thompson

Yes. So why then did you say that TVSes make simple problems difficult? That's plain wrong, and unsurprisingly you haven't been able to come up with the simpler solution to the (quite common) problem I presented. Because there is no simpler or lower cost solution than a TVS.

That wasn't the issue in this thread. We (and that includes the OP) have to live with what's available at Arrow, Digikey and so on. Clients do not have half a million bucks and one year of patience to wait for a better chip that then saves 15c in discretes, and maybe amortizes over a decade, or never. They want the solution here, now, and cheap. And they get that solution. That's life.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

I was just arguing that there's usually a clever approach that doesn't even need the expense of a TVS.

"Life" is good design, not patches. ...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
Reply to
Jim Thompson

Hi Jeorg,

That LTC part will likely blow up before the simple resistor+opto solution. The Ford load dump pulse is only 60V peak with 150ms decay time constant. The resistor+opto will survive 100V indefinitely. Furthermore is is extremely likely to survive pulses of much higher voltage, while the LTC part is extremely likely to fail.

Yes, of course you can make it still more robust with a R+TVS+R feeding the LED.

--

John Devereux
Reply to
John Devereux

[...]

No, you need the resistor (unless you are going to use an unreasonably large transorb). Load dump impedance is something like 2 ohms.

--

John Devereux
Reply to
John Devereux

[snip]
[snip]

Alternators have been improved over the years. In my day (mid '60's) you could see _400V_!

So, above 20V, my field driver devices turned off and went into BVCER mode and rode out load dump.

The control chip itself was low current, so a series carbon resistor plus an active "zener" on-chip sufficed for protection.

(Everything bipolar.) ...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
Reply to
Jim Thompson

There are some other test pulses defined with much higher peaks but these are much shorter - ~microseconds rather than ~100ms. And of course ESD is kV for ns. It might be well be wise to have TVS or capacitors in there for for these. And once you have all that what is the opto for?

--

John Devereux
Reply to
John Devereux

Board level designers do not have a chance to change the innards of a chip. The use of TVS on their part is typically a very smart move. In most cases there is no lower cost alternative, none.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

I only brought that link to show the shape of a load dump spike because some readers may not know. In aerospace those spikes are a whole lot tougher because the voltage can stay up there for a second, and it can happen several events in a row. This gets tested so a product that fails wouldn't even make it to field testing. And shouldn't.

Exactly. That's typically the lowest cost solution because TVS are ubiquitous and very cheap. Not using them is, in many cases, like driving around without wearing a seat belt.

[...] 
--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

The automobile industry seriously needs to address providing DC to their customers. They need a better connector instead of the cig plug, and the DC should be conditioned.

Ditto on transorb diodes.

Reply to
miso

For that sort of thing the auto industry tends to follow rather than lead... there are a few cars out there (SUVs, I believe) that provide standard 120V AC outlets, and I wouldn't be surprised if sooner or later you see some USB (5V) connections (many 3rd-party stereos already have a USB port for playing back music from memory sticks, for that matter)... but what would the conditioned

12V standard connector be?

The amateur radio guys like Anderson Powerpole connectors...

Reply to
Joel Koltner

...

0V AC

(5V)

ack

ned

Thanks again,

You guys are great!

I couldnt find any OPTO ssr's that seemed to be very tolerant.

would r-tvs-r-MMBD 7000-opto-LED be overkill. say an smbj33ca for the tvs?

Reply to
Johnny5

I like Anderson PP connectors too, but they're not standardised to a particular layout. I've seen red on left or right as 'standard' or convention. Red on left for 24V, red on right for 12V :) 'so many standards to choose from'...

Grant.

--
http://bugs.id.au/
Reply to
Grant

Not like you had much of a technology choice decades ago?

I pop TVS or zeners in stuff destined to be connected to 12 or 24V traction battery powered gear -- some nasty spikes in there too, including reversed battery.

Grant.

--
http://bugs.id.au/
Reply to
Grant

And what about the yammerheads that insist on plugging 700 W inverters into them?

Reply to
JosephKK

That's where two wonderful inventions come into play: Fuses and breakers :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.