13.11.8.7 Voltage References System (VREF) Control
| Name: | VREF |
| Offset: | 0x1C |
| Reset: | 0x00000000 |
| Property: | PAC Write-Protection |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| Access | |||||||||
| Reset |
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| SEL[3:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | |||||
| Reset | 0 | 0 | 0 | 0 | |||||
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| Access | |||||||||
| Reset |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| ONDEMAND | RUNSTDBY | VREFOE | TSEN | ||||||
| Access | R/W | R/W | R/W | R/W | |||||
| Reset | 0 | 0 | 0 | 0 |
Bits 19:16 – SEL[3:0] Voltage Reference Selection
These bits select the Voltage Reference for the ADC/SDADC.
Note:
- 2.0V to 2.5V can be used when the supply voltage (VDDANA) is higher than 2.7V.
| Value | Description |
|---|---|
| 0x0 | 1.0V voltage reference typical value |
| 0x1 | 1.1V voltage reference typical value |
| 0x2 | 1.2V voltage reference typical value |
| 0x3 | 1.25V voltage reference typical value |
| 0x4 | 2.0V voltage reference typical value |
| 0x5 | 2.2V voltage reference typical value |
| 0x6 | 2.4V voltage reference typical value |
| 0x7 | 2.5V voltage reference typical value |
| Others | Reserved |
Bit 7 – ONDEMAND On Demand Control
The On Demand operation mode allows for enabling or disabling the voltage reference depending on the peripheral requests.
| Value | Description |
|---|---|
| 0 | The voltage reference is always on, if enabled. |
| 1 | The voltage reference is enabled when a peripheral is requesting it. The voltage reference is disabled if no peripheral is requesting it. |
Bit 6 – RUNSTDBY Run In Standby
The bit controls how the voltage reference behaves during the standby sleep mode.
| Value | Description |
|---|---|
| 0 | The voltage reference is halted during standby sleep mode. |
| 1 | The voltage reference is not stopped in standby sleep mode. If VREF.ONDEMAND = 1, the voltage reference will be running when a peripheral is requesting it. If VREF.ONDEMAND = 0, the voltage reference will always be running in standby sleep mode. |
Bit 2 – VREFOE Voltage Reference Output Enable
| Value | Description |
|---|---|
| 0 | The Voltage Reference output is not available as an ADC input channel. |
| 1 | The Voltage Reference output is routed to an ADC input channel. |
Bit 1 – TSEN Temperature Sensor Enable
| Value | Description |
|---|---|
| 0 | Temperature Sensor is disabled. |
| 1 | Temperature Sensor is enabled and routed to an ADC input channel. |