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5v tolerant feature of lpc2106

Started by kanok53 May 16, 2009
hi, i'm recently working on a project where i'm using LPC2106 uc. i've interfaced it with various ics which are powered by 5v supply but facing some problem in it. some of its pins which r driving some 5 volt powered pin of other ic, seem to be damaged. but olimex's datasheet clearly suggesting that LPC2106 has 5v tolerant I/O features. so what might be the fault in my case? thanks in advance.

An Engineer's Guide to the LPC2100 Series

kanok53 wrote:
> hi, i'm recently working on a project where i'm using LPC2106 uc. i've interfaced it with various ics which are powered by 5v supply but facing some problem in it. some of its pins which r driving some 5 volt powered pin of other ic, seem to be damaged. but olimex's datasheet clearly suggesting that LPC2106 has 5v tolerant I/O features. so what might be the fault in my case? thanks in advance.

Some more details on what you've done would be useful.

5V tolerance is really an input spec. It doen't mean the pins will
drive 5V.

Robert

--
http://www.aeolusdevelopment.com/

From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time? 37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."
--- In l..., Robert Adsett wrote:
>
> kanok53 wrote:
> > hi, i'm recently working on a project where i'm using LPC2106 uc. i've interfaced it with various ics which are powered by 5v supply but facing some problem in it. some of its pins which r driving some 5 volt powered pin of other ic, seem to be damaged. but olimex's datasheet clearly suggesting that LPC2106 has 5v tolerant I/O features. so what might be the fault in my case? thanks in advance.
>
> Some more details on what you've done would be useful.
>
> 5V tolerance is really an input spec. It doen't mean the pins will
> drive 5V.
>
> Robert
>
> --
> http://www.aeolusdevelopment.com/
>
> From the Divided by a Common Language File (Edited to protect the guilty)
> ME - "I'd like to get Price and delivery for connector Part # XXXXX"
> Dist./Rep - "$X.XX Lead time 37 days"
> ME - "Anything we can do about lead time? 37 days seems a bit high."
> Dist./Rep - "that is the lead time given because our stock is live....
> we currently have stock."
>
at first thanking you to response to my post.
actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by lpc2106's 3 pins in three different board. 2 of them working very nicely so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving the s1 of mux properly. but i've found no problem in either code(cz its the same program) or in hardware(cz i've tried in the same hardware by replacing only the mcu lpc2106). so what could be the problem?
thanks again in advance.

----- Original Message -----
From: "kanok53"
To:
Sent: Monday, May 18, 2009 10:44 AM
Subject: [lpc2000] Re: 5v tolerant feature of lpc2106
> at first thanking you to response to my post.
> actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by
> lpc2106's 3 pins in three different board. 2 of them working very nicely
> so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving
> the s1 of mux properly. but i've found no problem in either code(cz its
> the same program) or in hardware(cz i've tried in the same hardware by
> replacing only the mcu lpc2106). so what could be the problem?

Will a 74LS input work with a 3.3V CMOS output?

Leon

according the 74LS151 datasheet a minimun of 2.0v input is required for the device to work

Regards

Jean-Jacques
--- In l..., "leon Heller" wrote:
>
> ----- Original Message -----
> From: "kanok53"
> To:
> Sent: Monday, May 18, 2009 10:44 AM
> Subject: [lpc2000] Re: 5v tolerant feature of lpc2106
> > at first thanking you to response to my post.
> > actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by
> > lpc2106's 3 pins in three different board. 2 of them working very nicely
> > so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving
> > the s1 of mux properly. but i've found no problem in either code(cz its
> > the same program) or in hardware(cz i've tried in the same hardware by
> > replacing only the mcu lpc2106). so what could be the problem?
>
> Will a 74LS input work with a 3.3V CMOS output?
>
> Leon
>

--- In l..., "leon Heller" wrote:
>
> ----- Original Message -----
> From: "kanok53"
> To:
> Sent: Monday, May 18, 2009 10:44 AM
> Subject: [lpc2000] Re: 5v tolerant feature of lpc2106
> > at first thanking you to response to my post.
> > actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by
> > lpc2106's 3 pins in three different board. 2 of them working very nicely
> > so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving
> > the s1 of mux properly. but i've found no problem in either code(cz its
> > the same program) or in hardware(cz i've tried in the same hardware by
> > replacing only the mcu lpc2106). so what could be the problem?
>
> Will a 74LS input work with a 3.3V CMOS output?

ya it works with a 3.3V CMOS output as 2 of my boards are still working. but as my another board got damaged(only one of those 3 pins which are driving selection line of mux) so i'm little bit worried about other two boards. I need the explanation of getting the pin damaged so that i can change my design if it demands. any hints of explanation of this matter will be helpful for me. thanks in advance.
>
> Leon
>

kanok53 wrote:
> --- In l..., "leon Heller" wrote:
>> ----- Original Message -----
>> From: "kanok53"
>> To:
>> Sent: Monday, May 18, 2009 10:44 AM
>> Subject: [lpc2000] Re: 5v tolerant feature of lpc2106
>>> at first thanking you to response to my post.
>>> actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by
>>> lpc2106's 3 pins in three different board. 2 of them working very nicely
>>> so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving
>>> the s1 of mux properly. but i've found no problem in either code(cz its
>>> the same program) or in hardware(cz i've tried in the same hardware by
>>> replacing only the mcu lpc2106). so what could be the problem?
>> Will a 74LS input work with a 3.3V CMOS output?
>
> ya it works with a 3.3V CMOS output as 2 of my boards are still working. but as my another board got damaged(only one of those 3 pins which are driving selection line of mux) so i'm little bit worried about other two boards. I need the explanation of getting the pin damaged so that i can change my design if it demands. any hints of explanation of this matter will be helpful for me. thanks in advance.

A test like that provides very little evidence, but another poster
pointed out the threshold was 2V.

So, these are three identical boards populated in the same fashion?

What three pins are being used?

They only drive the mux selection lines?

If you are using standard output pins to drive only single logic inputs
then your pin did not fail because of the load it was expected to drive.
You are looking for something else (construction fault, static).

Robert
--
http://www.aeolusdevelopment.com/

From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time? 37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."
--- In l..., Robert Adsett wrote:
>
> kanok53 wrote:
> > --- In l..., "leon Heller" wrote:
> >> ----- Original Message -----
> >> From: "kanok53"
> >> To:
> >> Sent: Monday, May 18, 2009 10:44 AM
> >> Subject: [lpc2000] Re: 5v tolerant feature of lpc2106
> >>> at first thanking you to response to my post.
> >>> actually i'm driving mux(74ls151) selection line(s0,s1,s2) pins by
> >>> lpc2106's 3 pins in three different board. 2 of them working very nicely
> >>> so far. but one of it doesn't, cz one of the pin of lpc2106 is not driving
> >>> the s1 of mux properly. but i've found no problem in either code(cz its
> >>> the same program) or in hardware(cz i've tried in the same hardware by
> >>> replacing only the mcu lpc2106). so what could be the problem?
> >> Will a 74LS input work with a 3.3V CMOS output?
> >
> > ya it works with a 3.3V CMOS output as 2 of my boards are still working. but as my another board got damaged(only one of those 3 pins which are driving selection line of mux) so i'm little bit worried about other two boards. I need the explanation of getting the pin damaged so that i can change my design if it demands. any hints of explanation of this matter will be helpful for me. thanks in advance.
>
> A test like that provides very little evidence, but another poster
> pointed out the threshold was 2V.
>
> So, these are three identical boards populated in the same fashion?
>
> What three pins are being used?
>
> They only drive the mux selection lines?
>
> If you are using standard output pins to drive only single logic inputs
> then your pin did not fail because of the load it was expected to drive.
> You are looking for something else (construction fault, static).
>
> Robert
> --
> http://www.aeolusdevelopment.com/
>
> From the Divided by a Common Language File (Edited to protect the guilty)
> ME - "I'd like to get Price and delivery for connector Part # XXXXX"
> Dist./Rep - "$X.XX Lead time 37 days"
> ME - "Anything we can do about lead time? 37 days seems a bit high."
> Dist./Rep - "that is the lead time given because our stock is live....
> we currently have stock."
>
thanks for ur elaborated explanation.
yes, i've designed three boards identically for three robots.
i'm using p0.28, p0.29 & p0.30 for this purpose and surely as standard ouput, nothing else.
what do u mean by construction problem or static charge problem?

kanok53 wrote:
> thanks for ur elaborated explanation.

Spell your words out correctly please. You are not limited here by a
SMS buffer.

> yes, i've designed three boards identically for three robots.
> i'm using p0.28, p0.29 & p0.30 for this purpose and surely as standard ouput, nothing else.
> what do u mean by construction problem or static charge problem?

Construction problems are things such as shorts or opens. Poorly
soldered pins or solder bridges. Could be caused by poor construction
technique or via too close to pads. Check that you don't have a low
resistance path to ground.

Static charge problem. I am referring to damage caused by static
discharge into device pins. If you've changed the micro the mux vould
still be damaged.

One fairly basic technique for checking would be to remove the mux and
check to see if the micro's pin will toggle. That should also make it
easy to check for solder bridges where the mux used to be. A DMM will
help check for bridges elsewhere.

Robert

--
http://www.aeolusdevelopment.com/

From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time? 37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."
--- In l..., "kanok53" wrote:
>
> hi, i'm recently working on a project where i'm using LPC2106 uc. i've interfaced it with various ics which are powered by 5v supply but facing some problem in it. some of its pins which r driving some 5 volt powered pin of other ic, seem to be damaged. but olimex's datasheet clearly suggesting that LPC2106 has 5v tolerant I/O features. so what might be the fault in my case? thanks in advance.
>

The pins are only 5V tolerant if Vdd3 is present. There can be no situation when the external 5V logic is powered while the uC is not.

I tend to use 330 ohm series resistors between uC pins and external things. The resistance is low enough not to cause much signal degradation but high enough to limit current flow should the resistor be shorted to ground.

Look at the pins with a scope and see what is happening.

I doubt it is a problem but make sure the uC and the MUX share a common Vss,

Richard