AREF above operating voltage of the microcontroller
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
add a comment |
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
2
What does the datasheet say?
– Elliot Alderson
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
3
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.
– Bimpelrekkie
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
2
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.
– Bimpelrekkie
2 hours ago
add a comment |
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
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 2 hours ago
Petru-Sebastian ToaderPetru-Sebastian Toader
907
907
2
What does the datasheet say?
– Elliot Alderson
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
3
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.
– Bimpelrekkie
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
2
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.
– Bimpelrekkie
2 hours ago
add a comment |
2
What does the datasheet say?
– Elliot Alderson
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
3
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.
– Bimpelrekkie
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
2
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.
– Bimpelrekkie
2 hours ago
2
2
What does the datasheet say?
– Elliot Alderson
2 hours ago
What does the datasheet say?
– Elliot Alderson
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
3
3
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.
– Bimpelrekkie
2 hours ago
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.
– Bimpelrekkie
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
2
2
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.
– Bimpelrekkie
2 hours ago
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.
– Bimpelrekkie
2 hours ago
add a comment |
1 Answer
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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
add a comment |
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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
add a comment |
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
add a comment |
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
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 2 hours ago
BimpelrekkieBimpelrekkie
47.1k240104
47.1k240104
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2
What does the datasheet say?
– Elliot Alderson
2 hours ago
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.
– Petru-Sebastian Toader
2 hours ago
3
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.
– Bimpelrekkie
2 hours ago
Thank you! I’ll use a voltage divider as it’s the best solution in my case.
– Petru-Sebastian Toader
2 hours ago
2
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.
– Bimpelrekkie
2 hours ago