Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 721
SAM9G20
39.3 Signal Description
39.4 Product Dependencies
39.4.1 Power Management
The ADC is automatically clocked after the first conversion in Normal Mode. In Sleep Mode, the ADC clock is automatically stopped after
each conversion. As the logic is small and the ADC cell can be put into Sleep Mode, the Power Management Controller has no effect on
the ADC behavior.
39.4.2 Interrupt Sources
The ADC interrupt line is connected on one of the internal sources of the Advanced Interrupt Controller. Using the ADC interrupt requires
the AIC to be programmed first.
39.4.3 Analog Inputs
The analog input pins can be multiplexed with PIO lines. In this case, the assignment of the ADC input is automatically done as soon as
the corresponding channel is enabled by writing the register ADC_CHER. By default, after reset, the PIO line is configured as input with
its pull-up enabled and the ADC input is connected to the GND.
39.4.4 I/O Lines
The pin ADTRG may be shared with other peripheral functions through the PIO Controller. In this case, the PIO Controller should be set
accordingly to assign the pin ADTRG to the ADC function.
39.4.5 Timer Triggers
Timer Counters may or may not be used as hardware triggers depending on user requirements. Thus, some or all of the timer counters
may be non-connected.
39.4.6 Conversion Performances
For performance and electrical characteristics of the ADC, see the DC Characteristics section.
39.5 Functional Description
39.5.1 Analog-to-digital Conversion
The ADC uses the ADC Clock to perform conversions. Converting a single analog value to a 10-bit digital data requires Sample and Hold
Clock cycles as defined in the field SHTIM of the “ADC Mode Register” and 10 ADC Clock cycles. The ADC Clock frequency is selected
in the PRESCAL field of the Mode Register (ADC_MR).
The ADC clock range is between MCK/2, if PRESCAL is 0, and MCK/128, if PRESCAL is set to 63 (0x3F). PRESCAL must be pro-
grammed in order to provide an ADC clock frequency according to the parameters given in the Product definition section.
39.5.2 Conversion Reference
The conversion is performed on a full range between 0V and the reference voltage pin ADVREF. Analog inputs between these voltages
convert to values based on a linear conversion.
Table 39-1: ADC Pin Description
Pin Name Description
VDDANA Analog power supply
ADVREF Reference voltage
AD0–AD3 Analog input channels
ADTRG External trigger