I am using a Atmel4SD32C processor.I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
For the main clock crystal Atmel specifiey the following requirements:
CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF CLOAD Internal Equivalent Load Capacitance Integrated load capacitance
(XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:--- Synchronet 3.20a-Linux NewsLink 1.114
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance
(XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
Thanks having contacted Microchip/Atmel they agreed!What exactly did they agree with, that their data sheet is not clear and they would improve on it?
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:When you say "series capacitors" do you mean this?
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator wouldn't start. I'd built it according to the Pink Book, which showed
two series capacitors as load - but the recommended value for each was
the total series load expected. Or vice versa, I can't recall. I got an answer from the guy at Motorola who worked with the main author, who confirmed the error in the book. Anyhow I changed the capacitors and it fired up right away.
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote:
On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator
wouldn't start. I'd built it according to the Pink Book, which showed
two series capacitors as load - but the recommended value for each was
the total series load expected. Or vice versa, I can't recall. I got an
answer from the guy at Motorola who worked with the main author, who
confirmed the error in the book. Anyhow I changed the capacitors and it
fired up right away.
When you say "series capacitors" do you mean this?
|| |++| ||
o---||---||||---||---o
|| |++| ||
The caps should go to ground, in parallel with the crystal in essence but series with each other.
|++|
o-+-----||||----+-o
| |++| |
| || || |
+--||--+--||--+
|| | ||
|
---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
On 15/11/18 9:20 am, gnuarm.deletethisbit@gmail.com wrote:I think we are saying the same thing.
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote:
On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator
wouldn't start. I'd built it according to the Pink Book, which showed
two series capacitors as load - but the recommended value for each was
the total series load expected. Or vice versa, I can't recall. I got an
answer from the guy at Motorola who worked with the main author, who
confirmed the error in the book. Anyhow I changed the capacitors and it
fired up right away.
When you say "series capacitors" do you mean this?
|| |++| ||
o----||---||||---||---o
|| |++| ||
No
The caps should go to ground, in parallel with the crystal in essence but series with each other.
The series combination still presents a C load to the crystal,
the fact that one node is earthed doesn't change that, because neither
of the other two is earthed. I recall needing two 33pF caps (series load about 16pF), not two 18pF (series 9pF).
|++|
o--+-----||||----+-o
| |++| |
| || || |
+--||--+--||--+
|| | ||
|
---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
It was 23 years ago. The recommended crystal load was wrong anyhow, ifI don't really need it as if I need an oscillator I usually use an oscillator rather than a crystal. But it is an interesting subject if you are interested in sharing.
you followed the Pink Book, and the oscillator wouldn't start. I can dig
out the book and the facts if you care.
On Wednesday, November 14, 2018 at 4:28:37 PM UTC-6, Clifford Heath wrote:
On 15/11/18 9:20 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote: >>>> On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>>>>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>>>>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator
wouldn't start. I'd built it according to the Pink Book, which showed
two series capacitors as load - but the recommended value for each was >>>> the total series load expected. Or vice versa, I can't recall. I got an >>>> answer from the guy at Motorola who worked with the main author, who
confirmed the error in the book. Anyhow I changed the capacitors and it >>>> fired up right away.
When you say "series capacitors" do you mean this?
|| |++| ||
o----||---||||---||---o
|| |++| ||
No
The caps should go to ground, in parallel with the crystal in essence but series with each other.
The series combination still presents a C load to the crystal,
the fact that one node is earthed doesn't change that, because neither
of the other two is earthed. I recall needing two 33pF caps (series load
about 16pF), not two 18pF (series 9pF).
I think we are saying the same thing.
|++|
o--+-----||||----+-o
| |++| |
| || || |
+--||--+--||--+
|| | ||
|
---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
It was 23 years ago. The recommended crystal load was wrong anyhow, if
you followed the Pink Book, and the oscillator wouldn't start. I can dig
out the book and the facts if you care.
I don't really need it as if I need an oscillator I usually use an oscillator rather than a crystal. But it is an interesting subject if you are interested in sharing.
I spent a fairly large amount of time once researching crystals to try to get to the derivation of the design issues. I found an HP paper that actually discussed the various crystal cuts in great detail. Not sure where it is, but I likely could find it if I dig enough.
On Wednesday, November 14, 2018 at 4:28:37 PM UTC-6, Clifford Heath wrote:
On 15/11/18 9:20 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote: >>>> On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote:
Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote:
I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements: >>>>>>>> CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance >>>>>>>> (XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator
wouldn't start. I'd built it according to the Pink Book, which showed
two series capacitors as load - but the recommended value for each was >>>> the total series load expected. Or vice versa, I can't recall. I got an >>>> answer from the guy at Motorola who worked with the main author, who
confirmed the error in the book. Anyhow I changed the capacitors and it >>>> fired up right away.
When you say "series capacitors" do you mean this?
|| |++| ||
o----||---||||---||---o
|| |++| ||
No
The caps should go to ground, in parallel with the crystal in essence but series with each other.
The series combination still presents a C load to the crystal,
the fact that one node is earthed doesn't change that, because neither
of the other two is earthed. I recall needing two 33pF caps (series load
about 16pF), not two 18pF (series 9pF).
I think we are saying the same thing.
|++|
o--+-----||||----+-o
| |++| |
| || || |
+--||--+--||--+
|| | ||
|
---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
It was 23 years ago. The recommended crystal load was wrong anyhow, if
you followed the Pink Book, and the oscillator wouldn't start. I can dig
out the book and the facts if you care.
I don't really need it as if I need an oscillator I usually use an oscillator rather than a crystal. But it is an interesting subject if you are interested in sharing.
I spent a fairly large amount of time once researching crystals to try to get to the derivation of the design issues. I found an HP paper that actually discussed the various crystal cuts in great detail. Not sure where it is, but I likely could find it if I dig enough.
Rick C.
Tesla referral code ---+- https://ts.la/richard11209
On 11/14/2018 18:57, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 4:28:37 PM UTC-6, Clifford Heath wrote:
On 15/11/18 9:20 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote:
On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote: >>>>>> Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote: >>>>>>>> I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements:
CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance
(XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum.
My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator >>>> wouldn't start. I'd built it according to the Pink Book, which showed >>>> two series capacitors as load - but the recommended value for each was >>>> the total series load expected. Or vice versa, I can't recall. I got an >>>> answer from the guy at Motorola who worked with the main author, who >>>> confirmed the error in the book. Anyhow I changed the capacitors and it >>>> fired up right away.
When you say "series capacitors" do you mean this?
|| |++| ||
o----||---||||---||---o
|| |++| ||
No
The caps should go to ground, in parallel with the crystal in essence but series with each other.
The series combination still presents a C load to the crystal,
the fact that one node is earthed doesn't change that, because neither
of the other two is earthed. I recall needing two 33pF caps (series load >> about 16pF), not two 18pF (series 9pF).
I think we are saying the same thing.
|++|
o--+-----||||----+-o
| |++| |
| || || |
+--||--+--||--+
|| | ||
|
---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
It was 23 years ago. The recommended crystal load was wrong anyhow, if
you followed the Pink Book, and the oscillator wouldn't start. I can dig >> out the book and the facts if you care.
I don't really need it as if I need an oscillator I usually use an oscillator rather than a crystal. But it is an interesting subject if you are interested in sharing.
I spent a fairly large amount of time once researching crystals to try to get to the derivation of the design issues. I found an HP paper that actually discussed the various crystal cuts in great detail. Not sure where it is, but I likely could find it if I dig enough.
Yep, that's the one. Thanks.Rick C.
Tesla referral code ---+- https://ts.la/richard11209
This? http://leapsecond.com/hpan/an200-2.pdf Google is your friend(tm)
On Thursday, November 15, 2018 at 10:18:51 AM UTC-5, Phil Martel wrote:
On 11/14/2018 18:57, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 4:28:37 PM UTC-6, Clifford Heath wrote: >>>> On 15/11/18 9:20 am, gnuarm.deletethisbit@gmail.com wrote:This? http://leapsecond.com/hpan/an200-2.pdf Google is your friend(tm)
On Wednesday, November 14, 2018 at 3:52:51 PM UTC-6, Clifford Heath wrote:
On 15/11/18 4:48 am, gnuarm.deletethisbit@gmail.com wrote:
On Wednesday, November 14, 2018 at 9:33:35 AM UTC-6, steve wrote: >>>>>>>> Thanks having contacted Microchip/Atmel they agreed!
On Monday, November 12, 2018 at 1:41:58 PM UTC, gnuarm.del...@gmail.com wrote:
On Monday, November 12, 2018 at 5:22:31 AM UTC-6, steve wrote: >>>>>>>>>> I am using a Atmel4SD32C processor.
For the main clock crystal Atmel specifiey the following requirements:
CLEXT
Maximum External Capacitor on XIN and XOUT 17 pF
Allowed Crystal Capacitance Load From crystal specification 12.5 – 17.5 pF
CLOAD Internal Equivalent Load Capacitance Integrated load capacitance
(XIN and XOUT in series) 7.5min 9.5typical 10.5 pFmax
Calculation for Cload external
CLEXT = 2 × (Ccrystal – CLOAD – CPCB).
Where CPCB is the capacitance of the printed circuit board (PCB) track layout from the crystal to the SAM4 pin
If I use a 12pf load crystal it would appear that no external capacitors to ground are needed.
Atmel give a max load capacitance of 17pf but no minimum. >>>>>>>>>> My pcb/pin tracks come in at about 2pf so I assume that is enough to start the oscillator and having tried it it seems to work fine
Is this ok? I assume this is what they intended when they designed in a internal load capacitor
I researched the issue of crystal selection with an Atmel MCU some years ago and found not only issues with figuring out the required load capacitance, but just as important the crystal ESR. As a result of my conversations with the sales person the factory added an ESR spec to the data sheet, but they did it as a table for different frequencies with no info on how to interpolate the specified data. Still, that was a good start.
Regarding your problem, I can't quite follow all the data you provided. Assuming you are interpreting the data correctly it does indeed seem that you need no additional capacitance. Just the same, I would recommend the addition of pads for adding capacitors, just in case.
Rick C.
https://ts.la/richard11209 - Tesla referral code
What exactly did they agree with, that their data sheet is not clear and they would improve on it?
This discussion reminds me of when my home-built MC68HC11 oscillator >>>>>> wouldn't start. I'd built it according to the Pink Book, which showed >>>>>> two series capacitors as load - but the recommended value for each was >>>>>> the total series load expected. Or vice versa, I can't recall. I got an >>>>>> answer from the guy at Motorola who worked with the main author, who >>>>>> confirmed the error in the book. Anyhow I changed the capacitors and it >>>>>> fired up right away.
When you say "series capacitors" do you mean this?
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o----||---||||---||---o
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No
The caps should go to ground, in parallel with the crystal in essence but series with each other.
The series combination still presents a C load to the crystal,
the fact that one node is earthed doesn't change that, because neither >>>> of the other two is earthed. I recall needing two 33pF caps (series load >>>> about 16pF), not two 18pF (series 9pF).
I think we are saying the same thing.
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o--+-----||||----+-o
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+--||--+--||--+
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---
V
Rick C.
Tesla referral code ----+ https://ts.la/richard11209
It was 23 years ago. The recommended crystal load was wrong anyhow, if >>>> you followed the Pink Book, and the oscillator wouldn't start. I can dig >>>> out the book and the facts if you care.
I don't really need it as if I need an oscillator I usually use an oscillator rather than a crystal. But it is an interesting subject if you are interested in sharing.
I spent a fairly large amount of time once researching crystals to try to get to the derivation of the design issues. I found an HP paper that actually discussed the various crystal cuts in great detail. Not sure where it is, but I likely could find it if I dig enough.
Rick C.
Tesla referral code ---+- https://ts.la/richard11209
Yep, that's the one. Thanks.
Rick C.
Tesla referral code +-+ https://ts.la/richard11209
I think that was written by Rick Karlquist, designer of the HP 10811
series OCXOs. He's a former SED regular and is still quite active on the time-nuts list. He also did a super interesting direct frequency
synthesizer based on cheap 455 kHz IF filters.
Cheers
Phil Hobbs
On 11/15/18 19:38, Phil Hobbs wrote:
I think that was written by Rick Karlquist, designer of the HP 10811
series OCXOs. He's a former SED regular and is still quite active on the time-nuts list. He also did a super interesting direct frequency synthesizer based on cheap 455 kHz IF filters.
Cheers
Phil Hobbs
A good book on crystal oscillators:
Crystal Oscillator Circuits, Robert J. Matthys
John Wiley, 1983, ISBN 0-471-87401-9
Chapters on crystals, various oscillator circuits
and plenty of practical examples. Not needed that
often but good to have in the bookshelf. My copy came
from abe books...
I've yet to see an analysis of digital oscillator circuits. I've seen one described but no real analysis of it. Performance is ok at lower frequencies (for undetermined values of "OK"), but no real measurements other than it was operable.
By "digital" I'm not talking about an inverter pressed into service as an amplifier. I mean a digital circuit mediated by software in the above case or it could be digital logic in other cases.
Rick C.
On 11/15/18 19:38, Phil Hobbs wrote:
I think that was written by Rick Karlquist, designer of the HP 10811
series OCXOs. He's a former SED regular and is still quite active on the
time-nuts list. He also did a super interesting direct frequency
synthesizer based on cheap 455 kHz IF filters.
Cheers
Phil Hobbs
A good book on crystal oscillators:
Crystal Oscillator Circuits, Robert J. Matthys
John Wiley, 1983, ISBN 0-471-87401-9
Chapters on crystals, various oscillator circuits
and plenty of practical examples. Not needed that
often but good to have in the bookshelf. My copy came
from abe books...
Chris
On 19.11.18 05:30, gnuarm.deletethisbit@gmail.com wrote:You are assuming facts not in evidence... in other words, you are talking through your hat. Drop all your misconceptions and think about it again. software and logic do not need to be clocked.
I've yet to see an analysis of digital oscillator circuits. I've seen one described but no real analysis of it. Performance is ok at lower frequencies (for undetermined values of "OK"), but no real measurements other than it was operable.
By "digital" I'm not talking about an inverter pressed into service as an amplifier. I mean a digital circuit mediated by software in the above case or it could be digital logic in other cases.
Rick C.
You're hunting unicorns here ...
The digital frequency generation circuits, aided by software
or not, are running behind some kind of clock. The clock is
ultimately from an analog time/frequency reference part, e.g.
a quartz crystal.
On Monday, November 19, 2018 at 4:01:56 AM UTC-5, Tauno Voipio wrote:
On 19.11.18 05:30, gnuarm.deletethisbit@gmail.com wrote:
I've yet to see an analysis of digital oscillator circuits. I've seen one described but no real analysis of it. Performance is ok at lower frequencies (for undetermined values of "OK"), but no real measurements other than it was operable.
By "digital" I'm not talking about an inverter pressed into service as an amplifier. I mean a digital circuit mediated by software in the above case or it could be digital logic in other cases.
Rick C.
You're hunting unicorns here ...
The digital frequency generation circuits, aided by software
or not, are running behind some kind of clock. The clock is
ultimately from an analog time/frequency reference part, e.g.
a quartz crystal.
You are assuming facts not in evidence... in other words, you are talking through your hat. Drop all your misconceptions and think about it again. software and logic do not need to be clocked.
If you were going to drive a crystal with a narrow pulse, what point in the cycle would it most beneficially be applied? Some of my thinking about this was inspired by reading about the Shortt–Synchronome free pendulum clock. It uses a gravity arm to supply an impulse every thirty swings of the main pendulum. I believe it is applied at the bottom of the swing. Whether that corresponds to the top of the crystal waveform or the midpoint depends on whether you consider position or velocity of the main pendulum.
I'm thinking the electrical analog would be the midpoint of the voltage sinewave.
Rick C.
Tesla referral code ---++ https://ts.la/richard11209
On 20.11.18 02:24, gnuarm.deletethisbit@gmail.com wrote:
On Monday, November 19, 2018 at 4:01:56 AM UTC-5, Tauno Voipio wrote:
On 19.11.18 05:30, gnuarm.deletethisbit@gmail.com wrote:
I've yet to see an analysis of digital oscillator circuits. I've seen one described but no real analysis of it. Performance is ok at lower frequencies (for undetermined values of "OK"), but no real measurements other than it was operable.
By "digital" I'm not talking about an inverter pressed into service as an amplifier. I mean a digital circuit mediated by software in the above case or it could be digital logic in other cases.
Rick C.
You're hunting unicorns here ...
The digital frequency generation circuits, aided by software
or not, are running behind some kind of clock. The clock is
ultimately from an analog time/frequency reference part, e.g.
a quartz crystal.
You are assuming facts not in evidence... in other words, you are talking through your hat. Drop all your misconceptions and think about it again. software and logic do not need to be clocked.
If you were going to drive a crystal with a narrow pulse, what point in the cycle would it most beneficially be applied? Some of my thinking about this was inspired by reading about the Shortt–Synchronome free pendulum clock. It uses a gravity arm to supply an impulse every thirty swings of the main pendulum. I believe it is applied at the bottom of the swing. Whether that corresponds to the top of the crystal waveform or the midpoint depends on whether you consider position or velocity of the main pendulum.
I'm thinking the electrical analog would be the midpoint of the voltage sinewave.
Rick C.
Tesla referral code ---++ https://ts.la/richard11209
So - you have the pendulum, which is equivalent to a resonator.There is no use of any timing delays of logic.
I like to quote Don Vonada, once the main designer at Digital
Equipment Corp. 'All digital parts are made of analog components'.
The oscillators made of digital gates are using the analog delays
in the gates a timing reference.
It is a completely different question, how the necessary energyVery much like the Shortt clock. I suggest you read a bit about it. It is very interesting and educational.
feed to the timing reference is applied, like kicking the crystal.
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