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The DAC can only maintain its output within one LSB of the desired value for approximately 100µs. When
a DAC is used to generate a static voltage or at a rate less than 20kSPS, the conversion must be
refreshed periodically. The OSCULP32K clock can start new conversions automatically after a specified
period. Write a value to the Refresh bit field in the DAC Control x register (DACCTRLx.REFRESH[3:0]) to
select the refresh period according to the formula:
REFRESH
= REFRESH ×
OSCULP32K
The actual period will depend on the tolerance of the OSCULP32K (see Electrical Characteristics).
If DACCTRLx.REFRESH=0, there is no conversion refresh. DACCTRLx.REFRESH=1 is Reserved.
If no new conversion is started before the refresh period is completed, DACx will convert the DATAx value
again.
In standby sleep mode, the refresh mode remains enabled if DACCTRLx.RUNSTDBY=1.
If DATAx is written while a refresh conversion is ongoing, the conversion of the new content of DATAx is
postponed until DACx is ready to start the next conversion.
47.6.9.4 Differential Mode
DAC0 and DAC1 can be configured to operate in differential mode, i.e. the combined output is a voltage
balanced around VREF/2, see also the figure below.
In differential mode, DAC0 and DAC1 are converting synchronously the DATA0 value. DATA0 must
therefore be a signed value, represented in two’s complement format with DATA0[11] as the signed bit.
DATA0 has therefore the range [-2047:2047].
VOUT0 is the positive output and VOUT1 the negative output. The differential output voltage is therefore:
OUT
=
DATA0
2047
× VREF =
OUT0
OUT1
DACCTRL0 serves as the configuration register for both DAC0 and DAC1. Therefore DACCTRL1 does
not need to be written.
The differential mode is enabled by writing a '1' to the Differential bit in the Control B register
(CTRLB.DIFF).
Figure 47-4. DAC Conversions in Differential Mode
2047 (0xFFF) VREF
0 (0x800) VREF/2
-2047 (0x000) 0
VOUT1
VOUT0
DATA0
SAM D5x/E5x Family Data Sheet
DAC – Digital-to-Analog Converter
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1680