What is the purpose of this extra PCB pad?
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1
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I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.
The datasheet is available here:
CMR200T Datasheet
This is the image in question:
Question:
- What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.
Any help would be appreciated, thanks!
pcb-design grounding surface-mount crystal
asked Dec 1 at 20:06
Matt
132
add a comment |
up vote
1
down vote
favorite
I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.
The datasheet is available here:
CMR200T Datasheet
This is the image in question:
Question:
- What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.
Any help would be appreciated, thanks!
pcb-design grounding surface-mount crystal
asked Dec 1 at 20:06
Matt
132
2
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.
The datasheet is available here:
CMR200T Datasheet
This is the image in question:
Question:
- What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.
Any help would be appreciated, thanks!
pcb-design grounding surface-mount crystal
asked Dec 1 at 20:06
Matt
132
I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.
The datasheet is available here:
CMR200T Datasheet
This is the image in question:
Question:
- What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.
Any help would be appreciated, thanks!
pcb-design grounding surface-mount crystal
pcb-design grounding surface-mount crystal
asked Dec 1 at 20:06
Matt
132
asked Dec 1 at 20:06
Matt
132
asked Dec 1 at 20:06
Matt
132
asked Dec 1 at 20:06
Matt
132
asked Dec 1 at 20:06
Matt
132
132
2
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06
add a comment |
2
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06
2
2
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06
add a comment |
2 Answers
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up vote
3
down vote
Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.
Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.
- If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
add a comment |
up vote
2
down vote
Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.
Double check though, and test continuity using a DMM
answered Dec 1 at 20:16
QuickishFM
756
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.
Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.
- If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
add a comment |
up vote
3
down vote
Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.
Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.
- If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
add a comment |
up vote
3
down vote
up vote
3
down vote
Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.
Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.
- If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
Primary reason is structural to prevent crystal mechanical shock and vibration damage or fatigue.
Since the Xtal is electrically isolated from the metal cylindrical case, it does not need an electrical gnd. It is just like the thru-hole parts with a wide can and very short leads where the can is electrically floating above the PCB surface.
- If 0V grounded, the added sub-pF stray capacitance load might reduce the frequency of x ppm which may be in the range of your average load-cap tolerances.
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
answered Dec 1 at 20:54
Tony EE rocketscientist
60.9k22192
60.9k22192
add a comment |
add a comment |
up vote
2
down vote
Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.
Double check though, and test continuity using a DMM
answered Dec 1 at 20:16
QuickishFM
756
add a comment |
up vote
2
down vote
Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.
Double check though, and test continuity using a DMM
answered Dec 1 at 20:16
QuickishFM
756
add a comment |
up vote
2
down vote
up vote
2
down vote
Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.
Double check though, and test continuity using a DMM
answered Dec 1 at 20:16
QuickishFM
756
Many large pads like those are used as grounding points; you could solder the case to it, or you could leave it as is. It provides a point that you can use as a ground for later use. You will see alot of these in consumer electronics such as laptops; chassis points are often connected securely to the mobo ground, which is why you can use chassis as ground in most cases.
Double check though, and test continuity using a DMM
answered Dec 1 at 20:16
QuickishFM
756
answered Dec 1 at 20:16
QuickishFM
756
answered Dec 1 at 20:16
QuickishFM
756
answered Dec 1 at 20:16
QuickishFM
756
756
add a comment |
add a comment |
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2
You solder the crystal case to it. See also: here.
– jonk
Dec 1 at 20:06