The 32.768kHz RTC is typically a tuning fork type.
The Xtals are typically characterized with load capacitances of 12pF
and 6pF.
Experience when tinkering with Philips I2C RTCs and other RTC
manufacturers , tells me that the 6pF load capacitance types seem to
be more accurate (stable) with these values. What determines this?
QUESTIONS
Q1
Is the LPC2000 RTC Osc characteristic, Cinput Xtal1, Xtal2 defined
anywhere in the Philps LPC2000 docs? They are defined in some of the
LPC900 data sheets. Why not the LPC2000?
How is the LPC2000 RTC Osc inputs characterised to achieve accurate
oscilation (timing) with minimal adjustment?
Should we rely on similar information on used in the I2C RTC IC's or,
is LPC2000 series RTC chracteristics different?
Q2
What are the desired parameters of of the 32.768kHz Xtals on LPC2000
devices (Load capacitances 12pf or 6pF types?), (22pF or 12pF
parallel caps) ?
Keil MCB2130 schematic has 22pF parallel caps
http://www.keil.com/mcb2130/mcb2130-schematics.pdf
Comment
Here are some Philips application notes on Xtals Osc on 8bit micro's
below.... where certain characteristics have been obtained from the
data sheets of Philips micros and I2c RTC clocks..... The data on the
input cpacitances, input impedances Gm of the IC is typically given.
http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN10289_1.pdf
X-tal oscillator on 8 bit microcontrollers AN96103 (1) and (2)
http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN96103_1.pdf
http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN97090_1.pdf
Philips I2C RTC Application note
http://www.standardics.philips.com/support/documents/i2c/pdf/an.real.time.clocks.pdf
===>It would be nice to seem some data gathered and documented for the
LPC2000 series to achieve accurate RTC operation.
Regards
Joe G.
--- In l..., "Leon Heller" wrote:
>
> ----- Original Message -----
> From: "Sean"
> To:
> Sent: Friday, February 10, 2006 12:28 AM
> Subject: [lpc2000] RTC Losing ~5 seconds per day
> > Hi All,
> >
> > I've got an LPC2148 set up and the RTC is losing about 5 seconds
per day,
> > I
> > am assuming that my crystal isn't exact.
> >
> > Are there any good ways to correct this? I know this isn't major,
but
> > that's 2 minutes a month, a little outside of what I'd like to
see.
>
> I've just bought some 32 kHz xtals. They seem to come in two types,
6 pF and
> 12 pF load capacitance, that could be the cause of
your problem.
Also, when
> used in watches they have a trimmer to set the
frequency exactly.
>
> Leon
>
LPC200 RTC Design for Accurate time
Started by ●June 19, 2006
Reply by ●June 21, 20062006-06-21
The accuracy of the crystal is specified in parts per million (ppm) from the
manufacturer. It is also dependant on the load capacitors. More
capacitance than specified will make the crystal run slow (or possibly not
startup or take a long time to do so). The big benefit for lower
capacitance is that the RTC battery will last longer because these
capacitors have to be charged and discharged @ 32.768kHz. The LPC is a
relative heater compared to other RTC chips (40 A) Thew LPC will
consume a 2032 coin lithium cell (200mah) in 5,000 hours (6.8 months). I
used an external IC because of that
Bennett
_____
From: l... [mailto:l...] On Behalf Of
phlpcmicro
Sent: Monday, June 19, 2006 9:14 AM
To: l...
Subject: [lpc2000] LPC200 RTC Design for Accurate time
The 32.768kHz RTC is typically a tuning fork type.
The Xtals are typically characterized with load capacitances of 12pF
and 6pF.
Experience when tinkering with Philips I2C RTCs and other RTC
manufacturers , tells me that the 6pF load capacitance types seem to
be more accurate (stable) with these values. What determines this?
QUESTIONS
Q1
Is the LPC2000 RTC Osc characteristic, Cinput Xtal1, Xtal2 defined
anywhere in the Philps LPC2000 docs? They are defined in some of the
LPC900 data sheets. Why not the LPC2000?
How is the LPC2000 RTC Osc inputs characterised to achieve accurate
oscilation (timing) with minimal adjustment?
Should we rely on similar information on used in the I2C RTC IC's or,
is LPC2000 series RTC chracteristics different?
Q2
What are the desired parameters of of the 32.768kHz Xtals on LPC2000
devices (Load capacitances 12pf or 6pF types?), (22pF or 12pF
parallel caps) ?
Keil MCB2130 schematic has 22pF parallel caps
http://www.keil.
com/mcb2130/mcb2130-schematics.pdf
Comment
Here are some Philips application notes on Xtals Osc on 8bit micro's
below.... where certain characteristics have been obtained from the
data sheets of Philips micros and I2c RTC clocks..... The data on the
input cpacitances, input impedances Gm of the IC is typically given.
http://www.semicond
0289_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN10289_1.pdf
X-tal oscillator on 8 bit microcontrollers AN96103 (1) and (2)
http://www.semicond
6103_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN96103_1.pdf
http://www.semicond
7090_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN97090_1.pdf
Philips I2C RTC Application note
http://www.standard
locks.pdf> ics.philips.com/support/documents/i2c/pdf/an.real.time.clocks.pdf
===>It would be nice to seem some data gathered and documented for the
LPC2000 series to achieve accurate RTC operation.
Regards
Joe G.
--- In lpc2000@yahoogroups .com, "Leon
Heller" wrote:
>
> ----- Original Message -----
> From: "Sean"
> To: .com>
> Sent: Friday, February 10, 2006 12:28 AM
> Subject: [lpc2000] RTC Losing ~5 seconds per day
>
>
> > Hi All,
> >
> > I've got an LPC2148 set up and the RTC is losing about 5 seconds
per day,
> > I
> > am assuming that my crystal isn't exact.
> >
> > Are there any good ways to correct this? I know this isn't major, but
> > that's 2 minutes a month, a little outside of what I'd like to see.
>
> I've just bought some 32 kHz xtals. They seem to come in two types,
6 pF and
> 12 pF load capacitance, that could be the cause of your problem.
Also, when
> used in watches they have a trimmer to set the frequency exactly.
>
> Leon
>
manufacturer. It is also dependant on the load capacitors. More
capacitance than specified will make the crystal run slow (or possibly not
startup or take a long time to do so). The big benefit for lower
capacitance is that the RTC battery will last longer because these
capacitors have to be charged and discharged @ 32.768kHz. The LPC is a
relative heater compared to other RTC chips (40 A) Thew LPC will
consume a 2032 coin lithium cell (200mah) in 5,000 hours (6.8 months). I
used an external IC because of that
Bennett
_____
From: l... [mailto:l...] On Behalf Of
phlpcmicro
Sent: Monday, June 19, 2006 9:14 AM
To: l...
Subject: [lpc2000] LPC200 RTC Design for Accurate time
The 32.768kHz RTC is typically a tuning fork type.
The Xtals are typically characterized with load capacitances of 12pF
and 6pF.
Experience when tinkering with Philips I2C RTCs and other RTC
manufacturers , tells me that the 6pF load capacitance types seem to
be more accurate (stable) with these values. What determines this?
QUESTIONS
Q1
Is the LPC2000 RTC Osc characteristic, Cinput Xtal1, Xtal2 defined
anywhere in the Philps LPC2000 docs? They are defined in some of the
LPC900 data sheets. Why not the LPC2000?
How is the LPC2000 RTC Osc inputs characterised to achieve accurate
oscilation (timing) with minimal adjustment?
Should we rely on similar information on used in the I2C RTC IC's or,
is LPC2000 series RTC chracteristics different?
Q2
What are the desired parameters of of the 32.768kHz Xtals on LPC2000
devices (Load capacitances 12pf or 6pF types?), (22pF or 12pF
parallel caps) ?
Keil MCB2130 schematic has 22pF parallel caps
http://www.keil.
com/mcb2130/mcb2130-schematics.pdf
Comment
Here are some Philips application notes on Xtals Osc on 8bit micro's
below.... where certain characteristics have been obtained from the
data sheets of Philips micros and I2c RTC clocks..... The data on the
input cpacitances, input impedances Gm of the IC is typically given.
http://www.semicond
0289_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN10289_1.pdf
X-tal oscillator on 8 bit microcontrollers AN96103 (1) and (2)
http://www.semicond
6103_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN96103_1.pdf
http://www.semicond
7090_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN97090_1.pdf
Philips I2C RTC Application note
http://www.standard
locks.pdf> ics.philips.com/support/documents/i2c/pdf/an.real.time.clocks.pdf
===>It would be nice to seem some data gathered and documented for the
LPC2000 series to achieve accurate RTC operation.
Regards
Joe G.
--- In lpc2000@yahoogroups .com, "Leon
Heller" wrote:
>
> ----- Original Message -----
> From: "Sean"
> To: .com>
> Sent: Friday, February 10, 2006 12:28 AM
> Subject: [lpc2000] RTC Losing ~5 seconds per day
>
>
> > Hi All,
> >
> > I've got an LPC2148 set up and the RTC is losing about 5 seconds
per day,
> > I
> > am assuming that my crystal isn't exact.
> >
> > Are there any good ways to correct this? I know this isn't major, but
> > that's 2 minutes a month, a little outside of what I'd like to see.
>
> I've just bought some 32 kHz xtals. They seem to come in two types,
6 pF and
> 12 pF load capacitance, that could be the cause of your problem.
Also, when
> used in watches they have a trimmer to set the frequency exactly.
>
> Leon
>
Reply by ●June 22, 20062006-06-22
Just a comment, why don't they design in an pll to create the cpu clock
from the rtc clock, could save a xtal. and rtc xtals are smaller in general.
Johan
----- Original Message -----
From: Bennett Scharf
To: l...
Sent: Monday, June 19, 2006 5:43 PM
Subject: RE: [lpc2000] LPC200 RTC Design for Accurate time
The accuracy of the crystal is specified in parts per million (ppm) from the
manufacturer. It is also dependant on the load capacitors. More
capacitance than specified will make the crystal run slow (or possibly not
startup or take a long time to do so). The big benefit for lower
capacitance is that the RTC battery will last longer because these
capacitors have to be charged and discharged @ 32.768kHz. The LPC is a
relative "heater" compared to other RTC chips (40 A) Thew LPC will
consume a 2032 coin lithium cell (200mah) in 5,000 hours (6.8 months). I
used an external IC because of that
Bennett
_____
From: l... [mailto:l...] On Behalf Of
phlpcmicro
Sent: Monday, June 19, 2006 9:14 AM
To: l...
Subject: [lpc2000] LPC200 RTC Design for Accurate time
The 32.768kHz RTC is typically a tuning fork type.
The Xtals are typically characterized with load capacitances of 12pF
and 6pF.
Experience when tinkering with Philips I2C RTCs and other RTC
manufacturers , tells me that the 6pF load capacitance types seem to
be more accurate (stable) with these values. What determines this?
QUESTIONS
Q1
Is the LPC2000 RTC Osc characteristic, Cinput Xtal1, Xtal2 defined
anywhere in the Philps LPC2000 docs? They are defined in some of the
LPC900 data sheets. Why not the LPC2000?
How is the LPC2000 RTC Osc inputs characterised to achieve accurate
oscilation (timing) with minimal adjustment?
Should we rely on similar information on used in the I2C RTC IC's or,
is LPC2000 series RTC chracteristics different?
Q2
What are the desired parameters of of the 32.768kHz Xtals on LPC2000
devices (Load capacitances 12pf or 6pF types?), (22pF or 12pF
parallel caps) ?
Keil MCB2130 schematic has 22pF parallel caps
http://www.keil.
com/mcb2130/mcb2130-schematics.pdf
Comment
Here are some Philips application notes on Xtals Osc on 8bit micro's
below.... where certain characteristics have been obtained from the
data sheets of Philips micros and I2c RTC clocks..... The data on the
input cpacitances, input impedances Gm of the IC is typically given.
http://www.semicond
0289_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN10289_1.pdf
X-tal oscillator on 8 bit microcontrollers AN96103 (1) and (2)
http://www.semicond
6103_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN96103_1.pdf
http://www.semicond
7090_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN97090_1.pdf
Philips I2C RTC Application note
http://www.standard
locks.pdf> ics.philips.com/support/documents/i2c/pdf/an.real.time.clocks.pdf
===>It would be nice to seem some data gathered and documented for the
LPC2000 series to achieve accurate RTC operation.
Regards
Joe G.
--- In lpc2000@yahoogroups .com, "Leon
Heller" wrote:
>
> ----- Original Message -----
> From: "Sean"
> To: .com>
> Sent: Friday, February 10, 2006 12:28 AM
> Subject: [lpc2000] RTC Losing ~5 seconds per day
>
>
> > Hi All,
> >
> > I've got an LPC2148 set up and the RTC is losing about 5 seconds
per day,
> > I
> > am assuming that my crystal isn't exact.
> >
> > Are there any good ways to correct this? I know this isn't major, but
> > that's 2 minutes a month, a little outside of what I'd like to see.
>
> I've just bought some 32 kHz xtals. They seem to come in two types,
6 pF and
> 12 pF load capacitance, that could be the cause of your problem.
Also, when
> used in watches they have a trimmer to set the frequency exactly.
>
> Leon
>
Johan
----- Original Message -----
From: Bennett Scharf
To: l...
Sent: Monday, June 19, 2006 5:43 PM
Subject: RE: [lpc2000] LPC200 RTC Design for Accurate time
The accuracy of the crystal is specified in parts per million (ppm) from the
manufacturer. It is also dependant on the load capacitors. More
capacitance than specified will make the crystal run slow (or possibly not
startup or take a long time to do so). The big benefit for lower
capacitance is that the RTC battery will last longer because these
capacitors have to be charged and discharged @ 32.768kHz. The LPC is a
relative "heater" compared to other RTC chips (40 A) Thew LPC will
consume a 2032 coin lithium cell (200mah) in 5,000 hours (6.8 months). I
used an external IC because of that
Bennett
_____
From: l... [mailto:l...] On Behalf Of
phlpcmicro
Sent: Monday, June 19, 2006 9:14 AM
To: l...
Subject: [lpc2000] LPC200 RTC Design for Accurate time
The 32.768kHz RTC is typically a tuning fork type.
The Xtals are typically characterized with load capacitances of 12pF
and 6pF.
Experience when tinkering with Philips I2C RTCs and other RTC
manufacturers , tells me that the 6pF load capacitance types seem to
be more accurate (stable) with these values. What determines this?
QUESTIONS
Q1
Is the LPC2000 RTC Osc characteristic, Cinput Xtal1, Xtal2 defined
anywhere in the Philps LPC2000 docs? They are defined in some of the
LPC900 data sheets. Why not the LPC2000?
How is the LPC2000 RTC Osc inputs characterised to achieve accurate
oscilation (timing) with minimal adjustment?
Should we rely on similar information on used in the I2C RTC IC's or,
is LPC2000 series RTC chracteristics different?
Q2
What are the desired parameters of of the 32.768kHz Xtals on LPC2000
devices (Load capacitances 12pf or 6pF types?), (22pF or 12pF
parallel caps) ?
Keil MCB2130 schematic has 22pF parallel caps
http://www.keil.
com/mcb2130/mcb2130-schematics.pdf
Comment
Here are some Philips application notes on Xtals Osc on 8bit micro's
below.... where certain characteristics have been obtained from the
data sheets of Philips micros and I2c RTC clocks..... The data on the
input cpacitances, input impedances Gm of the IC is typically given.
http://www.semicond
0289_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN10289_1.pdf
X-tal oscillator on 8 bit microcontrollers AN96103 (1) and (2)
http://www.semicond
6103_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN96103_1.pdf
http://www.semicond
7090_1.pdf>
uctors.philips.com/acrobat_download/applicationnotes/AN97090_1.pdf
Philips I2C RTC Application note
http://www.standard
locks.pdf> ics.philips.com/support/documents/i2c/pdf/an.real.time.clocks.pdf
===>It would be nice to seem some data gathered and documented for the
LPC2000 series to achieve accurate RTC operation.
Regards
Joe G.
--- In lpc2000@yahoogroups .com, "Leon
Heller" wrote:
>
> ----- Original Message -----
> From: "Sean"
> To: .com>
> Sent: Friday, February 10, 2006 12:28 AM
> Subject: [lpc2000] RTC Losing ~5 seconds per day
>
>
> > Hi All,
> >
> > I've got an LPC2148 set up and the RTC is losing about 5 seconds
per day,
> > I
> > am assuming that my crystal isn't exact.
> >
> > Are there any good ways to correct this? I know this isn't major, but
> > that's 2 minutes a month, a little outside of what I'd like to see.
>
> I've just bought some 32 kHz xtals. They seem to come in two types,
6 pF and
> 12 pF load capacitance, that could be the cause of your problem.
Also, when
> used in watches they have a trimmer to set the frequency exactly.
>
> Leon
>
