Hi All,
As advised by someone on this list, I looked up the NXP site for updated (July
2010) User Manual and Errata sheets for the LPC1765.
Among the errata listed, one is (and I quote without permission!):
**************************************
RTC.1: The Real Time Clock (RTC) does not work reliably within the
temperature specification
Introduction:
The RTC is a set of counters for measuring time when system power is on, and
optionally when it is off. The RTC is clocked by a separate 32 kHz oscillator
that produces a 1 Hz internal time reference. The RTC is powered by its own
power supply pin, VBAT, which can be connected to a battery, externally tied to
a 3 V supply, or left floating. The RTC can operate over temperature range from
−40 C to 85 C.
Problem:
The RTC does not work reliably within the temperature specification.
Work-around:
None.
**************************************
I have tried to understand from the above documentation snippet what the type of
failure may be, and the conditions under which it would be unreliable. I have
come up empty-handed.
This is most disturbing, since my design is absolutely dependent on the RTC for
various tasks, including wake-up from power-down. Does anyone here have more
details on this? All I can surmise is that it might not work at temperature
extremes, but even that is conjecture.
I have written to NXP technical support for clarity, but was wondering whether
anyone here already has more information. And if the problem is really as
serious as it seems, maybe some of us here would do better to change to another
processor...
--Ahmad
Disturbing errata for the LPC1765 RTC
Started by ●July 26, 2010
Reply by ●July 26, 20102010-07-26
On 26/07/2010 06:37, afolly_mil2 wrote:
> Problem:
> The RTC does not work reliably within the temperature specification.
...
> All I can surmise is that it might not work at temperature extremes,
> but even that is conjecture.
Yes, that seems to be what they are implying. Without specifics, which
do not appear to be provided, you simply can't rely on the RTC with this
chip. That's a serious problem!
Let us know if you hear back from NXP.
Pete
--
Pete Vidler
Senior Systems Developer,
TTE Systems Ltd
Work: http://www.tte-systems.com
Home: http://petevidler.com
> Problem:
> The RTC does not work reliably within the temperature specification.
...
> All I can surmise is that it might not work at temperature extremes,
> but even that is conjecture.
Yes, that seems to be what they are implying. Without specifics, which
do not appear to be provided, you simply can't rely on the RTC with this
chip. That's a serious problem!
Let us know if you hear back from NXP.
Pete
--
Pete Vidler
Senior Systems Developer,
TTE Systems Ltd
Work: http://www.tte-systems.com
Home: http://petevidler.com
Reply by ●July 26, 20102010-07-26
--- In l..., Sergio Sider wrote:
>
> I have a new design also what depends on RTC, the production started a month
> ago. I went using the LPC17xx in favour of the ones from Luminary I was used
> to (mainly because of flash size).
>
I noticed that the errata applies to parts with a '-' revision. That revision usually denotes pre-production parts doesn't it? Is that the latest revision that is currently shipping?
Regards,
Chris Burrows
CFB Software
Astrobe: LPC2xxx Oberon-07 Development System
http://www.astrobe.com
>
> I have a new design also what depends on RTC, the production started a month
> ago. I went using the LPC17xx in favour of the ones from Luminary I was used
> to (mainly because of flash size).
>
I noticed that the errata applies to parts with a '-' revision. That revision usually denotes pre-production parts doesn't it? Is that the latest revision that is currently shipping?
Regards,
Chris Burrows
CFB Software
Astrobe: LPC2xxx Oberon-07 Development System
http://www.astrobe.com
Reply by ●July 26, 20102010-07-26
Hi Chris,
I think it's the only revision available... at least that's what we received
from Digikey a few weeks ago.
And, I naively think that if there were other, the errata should have
mentioned.
I think and hope the problem is on the extremes of the temperature range.
But the errata only help us to be afraid.
Regards,
Sergio.
On Mon, Jul 26, 2010 at 10:21, cfbsoftware1 wrote:
> --- In l... , Sergio Sider
> wrote:
> >
> > I have a new design also what depends on RTC, the production started a
> month
> > ago. I went using the LPC17xx in favour of the ones from Luminary I was
> used
> > to (mainly because of flash size).
> > I noticed that the errata applies to parts with a '-' revision. That
> revision usually denotes pre-production parts doesn't it? Is that the latest
> revision that is currently shipping?
>
> Regards,
> Chris Burrows
> CFB Software
>
> Astrobe: LPC2xxx Oberon-07 Development System
> http://www.astrobe.com
>
>
>
I think it's the only revision available... at least that's what we received
from Digikey a few weeks ago.
And, I naively think that if there were other, the errata should have
mentioned.
I think and hope the problem is on the extremes of the temperature range.
But the errata only help us to be afraid.
Regards,
Sergio.
On Mon, Jul 26, 2010 at 10:21, cfbsoftware1 wrote:
> --- In l... , Sergio Sider
> wrote:
> >
> > I have a new design also what depends on RTC, the production started a
> month
> > ago. I went using the LPC17xx in favour of the ones from Luminary I was
> used
> > to (mainly because of flash size).
> > I noticed that the errata applies to parts with a '-' revision. That
> revision usually denotes pre-production parts doesn't it? Is that the latest
> revision that is currently shipping?
>
> Regards,
> Chris Burrows
> CFB Software
>
> Astrobe: LPC2xxx Oberon-07 Development System
> http://www.astrobe.com
>
>
>
Reply by ●July 26, 20102010-07-26
"cfbsoftware1" writes:
> --- In l..., Sergio Sider wrote:
>>
>> I have a new design also what depends on RTC, the production started
> a month
>> ago. I went using the LPC17xx in favour of the ones from Luminary I
> was used
>> to (mainly because of flash size).
>> I noticed that the errata applies to parts with a '-' revision. That
> revision usually denotes pre-production parts doesn't it? Is that the
> latest revision that is currently shipping?
The other parts seem to have the same errata, at least the LPC1768 does
:(
[...]
--
John Devereux
> --- In l..., Sergio Sider wrote:
>>
>> I have a new design also what depends on RTC, the production started
> a month
>> ago. I went using the LPC17xx in favour of the ones from Luminary I
> was used
>> to (mainly because of flash size).
>> I noticed that the errata applies to parts with a '-' revision. That
> revision usually denotes pre-production parts doesn't it? Is that the
> latest revision that is currently shipping?
The other parts seem to have the same errata, at least the LPC1768 does
:(
[...]
--
John Devereux
Reply by ●July 26, 20102010-07-26
Hi All,
That's the type of errata we were used to deal in LPC23XX for example.
I thought NXP got better with the LPC17XX... The errata was smaller than the
datasheet, a good sign.
I have a new design also what depends on RTC, the production started a month
ago. I went using the LPC17xx in favour of the ones from Luminary I was used
to (mainly because of flash size).
But then I read this updated errata. I never saw anything like that. It's
like "RTC is crap.. Workaround: Try another company"
Regards,
Sergio P. Sider
On Mon, Jul 26, 2010 at 02:37, afolly_mil2 wrote:
> Hi All,
>
> As advised by someone on this list, I looked up the NXP site for updated
> (July 2010) User Manual and Errata sheets for the LPC1765.
>
> Among the errata listed, one is (and I quote without permission!):
> **************************************
> RTC.1: The Real Time Clock (RTC) does not work reliably within the
> temperature specification
>
> Introduction:
> The RTC is a set of counters for measuring time when system power is on,
> and optionally when it is off. The RTC is clocked by a separate 32 kHz
> oscillator that produces a 1 Hz internal time reference. The RTC is powered
> by its own power supply pin, VBAT, which can be connected to a battery,
> externally tied to a 3 V supply, or left floating. The RTC can operate over
> temperature range from −40 C to 85 C.
>
> Problem:
> The RTC does not work reliably within the temperature specification.
>
> Work-around:
> None.
>
> **************************************
>
> I have tried to understand from the above documentation snippet what the
> type of failure may be, and the conditions under which it would be
> unreliable. I have come up empty-handed.
>
> This is most disturbing, since my design is absolutely dependent on the RTC
> for various tasks, including wake-up from power-down. Does anyone here have
> more details on this? All I can surmise is that it might not work at
> temperature extremes, but even that is conjecture.
>
> I have written to NXP technical support for clarity, but was wondering
> whether anyone here already has more information. And if the problem is
> really as serious as it seems, maybe some of us here would do better to
> change to another processor...
>
> --Ahmad
>
>
>
That's the type of errata we were used to deal in LPC23XX for example.
I thought NXP got better with the LPC17XX... The errata was smaller than the
datasheet, a good sign.
I have a new design also what depends on RTC, the production started a month
ago. I went using the LPC17xx in favour of the ones from Luminary I was used
to (mainly because of flash size).
But then I read this updated errata. I never saw anything like that. It's
like "RTC is crap.. Workaround: Try another company"
Regards,
Sergio P. Sider
On Mon, Jul 26, 2010 at 02:37, afolly_mil2 wrote:
> Hi All,
>
> As advised by someone on this list, I looked up the NXP site for updated
> (July 2010) User Manual and Errata sheets for the LPC1765.
>
> Among the errata listed, one is (and I quote without permission!):
> **************************************
> RTC.1: The Real Time Clock (RTC) does not work reliably within the
> temperature specification
>
> Introduction:
> The RTC is a set of counters for measuring time when system power is on,
> and optionally when it is off. The RTC is clocked by a separate 32 kHz
> oscillator that produces a 1 Hz internal time reference. The RTC is powered
> by its own power supply pin, VBAT, which can be connected to a battery,
> externally tied to a 3 V supply, or left floating. The RTC can operate over
> temperature range from −40 C to 85 C.
>
> Problem:
> The RTC does not work reliably within the temperature specification.
>
> Work-around:
> None.
>
> **************************************
>
> I have tried to understand from the above documentation snippet what the
> type of failure may be, and the conditions under which it would be
> unreliable. I have come up empty-handed.
>
> This is most disturbing, since my design is absolutely dependent on the RTC
> for various tasks, including wake-up from power-down. Does anyone here have
> more details on this? All I can surmise is that it might not work at
> temperature extremes, but even that is conjecture.
>
> I have written to NXP technical support for clarity, but was wondering
> whether anyone here already has more information. And if the problem is
> really as serious as it seems, maybe some of us here would do better to
> change to another processor...
>
> --Ahmad
>
>
>
Reply by ●July 26, 20102010-07-26
Pete Vidler writes:
> On 26/07/2010 06:37, afolly_mil2 wrote:
>> Problem:
> > The RTC does not work reliably within the temperature
> specification.
> ...
>> All I can surmise is that it might not work at temperature extremes,
>> but even that is conjecture.
>
> Yes, that seems to be what they are implying. Without specifics,
> which
> do not appear to be provided, you simply can't rely on the RTC with
> this
> chip. That's a serious problem!
>
> Let us know if you hear back from NXP.
What about the other chips in the 17xx family? Are they OK? We are
looking at switching but absolutely need the RTC to work!
--
John Devereux
> On 26/07/2010 06:37, afolly_mil2 wrote:
>> Problem:
> > The RTC does not work reliably within the temperature
> specification.
> ...
>> All I can surmise is that it might not work at temperature extremes,
>> but even that is conjecture.
>
> Yes, that seems to be what they are implying. Without specifics,
> which
> do not appear to be provided, you simply can't rely on the RTC with
> this
> chip. That's a serious problem!
>
> Let us know if you hear back from NXP.
What about the other chips in the 17xx family? Are they OK? We are
looking at switching but absolutely need the RTC to work!
--
John Devereux
Reply by ●July 26, 20102010-07-26
1751, 1752, 1754, 1756, 1758, 1759, 1763, 1764, 1765, 1766, 1768, 1769 all
have the problem mentioned in their Errata Sheets.
1767 does not have an errata doc updated in July 2010 like the others.
Either they will update it soon, or it is free of the problem.
I may end up back with the 2365 which is pin compatible... It will mean
losing out on the advantages that I was counting on in the 17xx family, but
at least it is a change that requires no PCB revision.
I consider this a HUGE goof-up by NXP.
But here's my speculation about it:
The 17xx series has brought the RTC power consumption down dramatically from
what it was in the 23xx series. The RTC circuit is therefore susceptible to
even very small leakage and parasitic currents. These are always a function
of temperature. Higher temperatures give rise to larger leakage currents,
which could disturb normal (ideal) operation of the transistors. I would
therefore think that towards the 70+ degree C mark, there may be
unreliability. In which case it would be good enough for more moderate
temperature use. On the other hand, junction voltage drops rise with lower
temperatures(at least for diodes), so this might also be a problem when
tuning the chip design for low low power. Also to be considered is that the
July 2010 edition of the Errata is Revision 4. This means that the problem
was not noticed or proven for quite a long time (since October 2009, a gap
of 9 months). I would think it is a very rare problem.
I'm hoping NXP tech support will be more specific about the problem. I'm
not throwing out my 1765 chips yet.
I'm also hoping that a chip revision will be out soon... fingers crossed. I
would really hate to have to change 10K LOC to have it run on another chip.
--Ahmad
On Mon, Jul 26, 2010 at 4:51 PM, John Devereux wrote:
> Pete Vidler > writes:
>
> > On 26/07/2010 06:37, afolly_mil2 wrote:
> >> Problem:
> > > The RTC does not work reliably within the temperature
> > specification.
> > ...
> >> All I can surmise is that it might not work at temperature extremes,
> >> but even that is conjecture.
> >
> > Yes, that seems to be what they are implying. Without specifics,
> > which
> > do not appear to be provided, you simply can't rely on the RTC with
> > this
> > chip. That's a serious problem!
> >
> > Let us know if you hear back from NXP.
>
> What about the other chips in the 17xx family? Are they OK? We are
> looking at switching but absolutely need the RTC to work!
>
> --
>
> John Devereux
>
>
>
have the problem mentioned in their Errata Sheets.
1767 does not have an errata doc updated in July 2010 like the others.
Either they will update it soon, or it is free of the problem.
I may end up back with the 2365 which is pin compatible... It will mean
losing out on the advantages that I was counting on in the 17xx family, but
at least it is a change that requires no PCB revision.
I consider this a HUGE goof-up by NXP.
But here's my speculation about it:
The 17xx series has brought the RTC power consumption down dramatically from
what it was in the 23xx series. The RTC circuit is therefore susceptible to
even very small leakage and parasitic currents. These are always a function
of temperature. Higher temperatures give rise to larger leakage currents,
which could disturb normal (ideal) operation of the transistors. I would
therefore think that towards the 70+ degree C mark, there may be
unreliability. In which case it would be good enough for more moderate
temperature use. On the other hand, junction voltage drops rise with lower
temperatures(at least for diodes), so this might also be a problem when
tuning the chip design for low low power. Also to be considered is that the
July 2010 edition of the Errata is Revision 4. This means that the problem
was not noticed or proven for quite a long time (since October 2009, a gap
of 9 months). I would think it is a very rare problem.
I'm hoping NXP tech support will be more specific about the problem. I'm
not throwing out my 1765 chips yet.
I'm also hoping that a chip revision will be out soon... fingers crossed. I
would really hate to have to change 10K LOC to have it run on another chip.
--Ahmad
On Mon, Jul 26, 2010 at 4:51 PM, John Devereux wrote:
> Pete Vidler > writes:
>
> > On 26/07/2010 06:37, afolly_mil2 wrote:
> >> Problem:
> > > The RTC does not work reliably within the temperature
> > specification.
> > ...
> >> All I can surmise is that it might not work at temperature extremes,
> >> but even that is conjecture.
> >
> > Yes, that seems to be what they are implying. Without specifics,
> > which
> > do not appear to be provided, you simply can't rely on the RTC with
> > this
> > chip. That's a serious problem!
> >
> > Let us know if you hear back from NXP.
>
> What about the other chips in the 17xx family? Are they OK? We are
> looking at switching but absolutely need the RTC to work!
>
> --
>
> John Devereux
>
>
>
Reply by ●July 26, 20102010-07-26
On Tue, 27 Jul 2010 01:22:54 +0530, you wrote:
>1751, 1752, 1754, 1756, 1758, 1759, 1763, 1764, 1765, 1766, 1768, 1769 all
>have the problem mentioned in their Errata Sheets.
>
>1767 does not have an errata doc updated in July 2010 like the others.
> Either they will update it soon, or it is free of the problem.
>
>I may end up back with the 2365 which is pin compatible... It will mean
>losing out on the advantages that I was counting on in the 17xx family, but
>at least it is a change that requires no PCB revision.
>
>I consider this a HUGE goof-up by NXP.
>
>But here's my speculation about it:
>
>The 17xx series has brought the RTC power consumption down dramatically from
>what it was in the 23xx series. The RTC circuit is therefore susceptible to
>even very small leakage and parasitic currents. These are always a function
>of temperature. Higher temperatures give rise to larger leakage currents,
>which could disturb normal (ideal) operation of the transistors. I would
>therefore think that towards the 70+ degree C mark, there may be
>unreliability. In which case it would be good enough for more moderate
>temperature use. On the other hand, junction voltage drops rise with lower
>temperatures(at least for diodes), so this might also be a problem when
>tuning the chip design for low low power. Also to be considered is that the
>July 2010 edition of the Errata is Revision 4. This means that the problem
>was not noticed or proven for quite a long time (since October 2009, a gap
>of 9 months). I would think it is a very rare problem.
..or a problem that only occurs on some production silicon.
>1751, 1752, 1754, 1756, 1758, 1759, 1763, 1764, 1765, 1766, 1768, 1769 all
>have the problem mentioned in their Errata Sheets.
>
>1767 does not have an errata doc updated in July 2010 like the others.
> Either they will update it soon, or it is free of the problem.
>
>I may end up back with the 2365 which is pin compatible... It will mean
>losing out on the advantages that I was counting on in the 17xx family, but
>at least it is a change that requires no PCB revision.
>
>I consider this a HUGE goof-up by NXP.
>
>But here's my speculation about it:
>
>The 17xx series has brought the RTC power consumption down dramatically from
>what it was in the 23xx series. The RTC circuit is therefore susceptible to
>even very small leakage and parasitic currents. These are always a function
>of temperature. Higher temperatures give rise to larger leakage currents,
>which could disturb normal (ideal) operation of the transistors. I would
>therefore think that towards the 70+ degree C mark, there may be
>unreliability. In which case it would be good enough for more moderate
>temperature use. On the other hand, junction voltage drops rise with lower
>temperatures(at least for diodes), so this might also be a problem when
>tuning the chip design for low low power. Also to be considered is that the
>July 2010 edition of the Errata is Revision 4. This means that the problem
>was not noticed or proven for quite a long time (since October 2009, a gap
>of 9 months). I would think it is a very rare problem.
..or a problem that only occurs on some production silicon.
Reply by ●July 26, 20102010-07-26
Hi Ahmad,
Your speculation makes sense. I had an 'invisible' problem with the RTC a
few weeks ago, on my first prototype. I am not quite sure of what happened
exactly but everything seems to show that it was dirt on the PCB (flux
residues,etc), that fortunately did not occurred on the production line. So,
the RTC circuitry is really sensible (much more than the LPC23 version and
other chips I used in the past).
More disturbing than the errata itself is the total lack of information
about the problem.
Regards,
Sergio.
On Mon, Jul 26, 2010 at 16:52, Ahmad wrote:
> 1751, 1752, 1754, 1756, 1758, 1759, 1763, 1764, 1765, 1766, 1768, 1769 all
> have the problem mentioned in their Errata Sheets.
>
> 1767 does not have an errata doc updated in July 2010 like the others.
> Either they will update it soon, or it is free of the problem.
>
> I may end up back with the 2365 which is pin compatible... It will mean
> losing out on the advantages that I was counting on in the 17xx family, but
> at least it is a change that requires no PCB revision.
>
> I consider this a HUGE goof-up by NXP.
>
> But here's my speculation about it:
>
> The 17xx series has brought the RTC power consumption down dramatically
> from what it was in the 23xx series. The RTC circuit is therefore
> susceptible to even very small leakage and parasitic currents. These are
> always a function of temperature. Higher temperatures give rise to larger
> leakage currents, which could disturb normal (ideal) operation of the
> transistors. I would therefore think that towards the 70+ degree C mark,
> there may be unreliability. In which case it would be good enough for more
> moderate temperature use. On the other hand, junction voltage drops rise
> with lower temperatures(at least for diodes), so this might also be a
> problem when tuning the chip design for low low power. Also to be
> considered is that the July 2010 edition of the Errata is Revision 4. This
> means that the problem was not noticed or proven for quite a long time
> (since October 2009, a gap of 9 months). I would think it is a very rare
> problem.
>
> I'm hoping NXP tech support will be more specific about the problem. I'm
> not throwing out my 1765 chips yet.
>
> I'm also hoping that a chip revision will be out soon... fingers crossed.
> I would really hate to have to change 10K LOC to have it run on another
> chip.
>
> --Ahmad
>
> On Mon, Jul 26, 2010 at 4:51 PM, John Devereux wrote:
>
>> Pete Vidler > writes:
>>
>> > On 26/07/2010 06:37, afolly_mil2 wrote:
>> >> Problem:
>> > > The RTC does not work reliably within the temperature
>> > specification.
>> > ...
>> >> All I can surmise is that it might not work at temperature extremes,
>> >> but even that is conjecture.
>> >
>> > Yes, that seems to be what they are implying. Without specifics,
>> > which
>> > do not appear to be provided, you simply can't rely on the RTC with
>> > this
>> > chip. That's a serious problem!
>> >
>> > Let us know if you hear back from NXP.
>>
>> What about the other chips in the 17xx family? Are they OK? We are
>> looking at switching but absolutely need the RTC to work!
>>
>> --
>>
>> John Devereux
>
>
Your speculation makes sense. I had an 'invisible' problem with the RTC a
few weeks ago, on my first prototype. I am not quite sure of what happened
exactly but everything seems to show that it was dirt on the PCB (flux
residues,etc), that fortunately did not occurred on the production line. So,
the RTC circuitry is really sensible (much more than the LPC23 version and
other chips I used in the past).
More disturbing than the errata itself is the total lack of information
about the problem.
Regards,
Sergio.
On Mon, Jul 26, 2010 at 16:52, Ahmad wrote:
> 1751, 1752, 1754, 1756, 1758, 1759, 1763, 1764, 1765, 1766, 1768, 1769 all
> have the problem mentioned in their Errata Sheets.
>
> 1767 does not have an errata doc updated in July 2010 like the others.
> Either they will update it soon, or it is free of the problem.
>
> I may end up back with the 2365 which is pin compatible... It will mean
> losing out on the advantages that I was counting on in the 17xx family, but
> at least it is a change that requires no PCB revision.
>
> I consider this a HUGE goof-up by NXP.
>
> But here's my speculation about it:
>
> The 17xx series has brought the RTC power consumption down dramatically
> from what it was in the 23xx series. The RTC circuit is therefore
> susceptible to even very small leakage and parasitic currents. These are
> always a function of temperature. Higher temperatures give rise to larger
> leakage currents, which could disturb normal (ideal) operation of the
> transistors. I would therefore think that towards the 70+ degree C mark,
> there may be unreliability. In which case it would be good enough for more
> moderate temperature use. On the other hand, junction voltage drops rise
> with lower temperatures(at least for diodes), so this might also be a
> problem when tuning the chip design for low low power. Also to be
> considered is that the July 2010 edition of the Errata is Revision 4. This
> means that the problem was not noticed or proven for quite a long time
> (since October 2009, a gap of 9 months). I would think it is a very rare
> problem.
>
> I'm hoping NXP tech support will be more specific about the problem. I'm
> not throwing out my 1765 chips yet.
>
> I'm also hoping that a chip revision will be out soon... fingers crossed.
> I would really hate to have to change 10K LOC to have it run on another
> chip.
>
> --Ahmad
>
> On Mon, Jul 26, 2010 at 4:51 PM, John Devereux wrote:
>
>> Pete Vidler > writes:
>>
>> > On 26/07/2010 06:37, afolly_mil2 wrote:
>> >> Problem:
>> > > The RTC does not work reliably within the temperature
>> > specification.
>> > ...
>> >> All I can surmise is that it might not work at temperature extremes,
>> >> but even that is conjecture.
>> >
>> > Yes, that seems to be what they are implying. Without specifics,
>> > which
>> > do not appear to be provided, you simply can't rely on the RTC with
>> > this
>> > chip. That's a serious problem!
>> >
>> > Let us know if you hear back from NXP.
>>
>> What about the other chips in the 17xx family? Are they OK? We are
>> looking at switching but absolutely need the RTC to work!
>>
>> --
>>
>> John Devereux
>
>
