Mixing
AREF above operating voltage of the microcontroller
$begingroup$
I’m operating an ATMega32 at 3v3 through USB and a LDO.
Is it possible to connect the AREF pin directly to the USB voltage of 5V so that I can read voltages between 0 and 5V when reading from the analog pins?
arduino avr
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
$endgroup$
add a comment |
$begingroup$
I’m operating an ATMega32 at 3v3 through USB and a LDO.
Is it possible to connect the AREF pin directly to the USB voltage of 5V so that I can read voltages between 0 and 5V when reading from the analog pins?
arduino avr
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
$endgroup$
4
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
3
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
3
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32
add a comment |
$begingroup$
I’m operating an ATMega32 at 3v3 through USB and a LDO.
Is it possible to connect the AREF pin directly to the USB voltage of 5V so that I can read voltages between 0 and 5V when reading from the analog pins?
arduino avr
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
$endgroup$
I’m operating an ATMega32 at 3v3 through USB and a LDO.
Is it possible to connect the AREF pin directly to the USB voltage of 5V so that I can read voltages between 0 and 5V when reading from the analog pins?
arduino avr
arduino avr
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
asked Jan 8 at 15:19
Petru-Sebastian ToaderPetru-Sebastian Toader
957
957
4
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
3
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
3
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32
add a comment |
4
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
3
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
3
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32
4
4
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
3
3
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
3
3
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit:
The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins.
The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting.
So if you connect 5 V to AREF, the VDD supply of the uC will be pulled up to about 4.4 V ! But you supplied 3.3 V via an LDO. Yes, then the LDO will do nothing.
If you want a 5 V input range either power the uC with 5 V
or
use a voltage divider to lower the input voltage to the ADC.
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
$endgroup$
add a comment |
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$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit:
The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins.
The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting.
So if you connect 5 V to AREF, the VDD supply of the uC will be pulled up to about 4.4 V ! But you supplied 3.3 V via an LDO. Yes, then the LDO will do nothing.
If you want a 5 V input range either power the uC with 5 V
or
use a voltage divider to lower the input voltage to the ADC.
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
$endgroup$
add a comment |
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit:
The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins.
The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting.
So if you connect 5 V to AREF, the VDD supply of the uC will be pulled up to about 4.4 V ! But you supplied 3.3 V via an LDO. Yes, then the LDO will do nothing.
If you want a 5 V input range either power the uC with 5 V
or
use a voltage divider to lower the input voltage to the ADC.
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
$endgroup$
add a comment |
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit:
The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins.
The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting.
So if you connect 5 V to AREF, the VDD supply of the uC will be pulled up to about 4.4 V ! But you supplied 3.3 V via an LDO. Yes, then the LDO will do nothing.
If you want a 5 V input range either power the uC with 5 V
or
use a voltage divider to lower the input voltage to the ADC.
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
$endgroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit:
The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins.
The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting.
So if you connect 5 V to AREF, the VDD supply of the uC will be pulled up to about 4.4 V ! But you supplied 3.3 V via an LDO. Yes, then the LDO will do nothing.
If you want a 5 V input range either power the uC with 5 V
or
use a voltage divider to lower the input voltage to the ADC.
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
answered Jan 8 at 15:33
BimpelrekkieBimpelrekkie
48.3k240107
48.3k240107
add a comment |
add a comment |
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4
$begingroup$
What does the datasheet say?
$endgroup$
– Elliot Alderson
Jan 8 at 15:22
$begingroup$
The microcontroller definitey can operate at 5V same applies to AREF it can operate under 5V, it is unclear to me if it can have a higher voltage than the one being fed through the VCC pins.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:28
3
$begingroup$
Indeed this information will be in the datasheet, but since it might be difficult to find I'll help a bit: The datasheet will state that the voltages at the uC's inputs/outputs cannot exceed the voltage on the VDD pins. The reason for this is the ESD protection diodes. As soon as the voltage at AREF becomes higher than VDD + 0.5 V the AREF's ESD diode will start conducting. If you want a 5 V input range either power the uC with 5 V or use a voltage divider to lower the input voltage to the ADC.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:28
$begingroup$
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
$endgroup$
– Petru-Sebastian Toader
Jan 8 at 15:31
3
$begingroup$
To learn more about what issues the ESD diodes can cause, watch this EEVBlog video: youtube.com/watch?v=2yFh7Vv0Paw Making this and comment above an answer because, well it is.
$endgroup$
– Bimpelrekkie
Jan 8 at 15:32