Table 104. Channel Output Modes Summary; Dac Channel Buffer Calibration - ST STM32L4x6 Reference Manual

RM0351
MODEx[2:0] Mode
0 0 0
0 0 1
Normal mode
0 1 0
0 1 1
1 0 0
1 0 1
Sample & hold
mode
1 1 0
1 1 1
17.3.11

DAC channel buffer calibration

The transfer function for an N-bit digital-to-analog converter (DAC) is
Where V
scale voltage, and V
Due to output buffer characteristics, the voltage offset may differ from part-to-part and
introduce an absolute offset error on the analog output. To compensate the V
is required by a trimming technique.
The calibration is only valid when the DAC channelx is operating with buffer enabled
(MODEx[2:0] = 000b or 001b or 100b or 101b). if applied in other modes when the buffer is
off, it has no effect. During the calibration:
•
The buffer output will be disconnected from the pin internal/external connections and
put in tristate mode (HiZ),
• The buffer will act as a comparator, to sense the middle-code value 0x800 and
compare it to VREF+/2 signal thru an internal bridge, then toggle its output signal to 0
or 1 depending on the comparison result (CAL_FLAGx bit)
Two calibration techniques are provided:
•
Factory trimming (always enabled)
The DAC buffer offset is factory trimmed. The default value of OTRIMx[4:0] bits in
DAC_CCR register is the factory trimming value and it is loaded once DAC digital interface
is reset.
•
User trimming
The user trimming can be done when the operating conditions differs from nominal factory
trimming conditions and in particular when VDD/VDDA voltage, temperature, VREF+ values
change and can be done at any point during application by software.

Table 104. Channel output modes summary

Buffer
Connected to external pin
Enabled
Connected to external pin and to on chip-peripherals (ex, comparators)
Connected to external pin
Disabled
Connected to on chip peripherals (ex, comparators)
Connected to external pin
Enabled
Connected to external pin and to on chip peripherals (ex, comparators)
Connected to external pin and to on chip peripherals (ex, comparators)
Disabled
Connected to on chip peripherals (ex, comparators)
(
V
=
out
is the analog output, D is the digital input, G is the gain, V
out
is the offset voltage.For an ideal DAC channel, G = 1 and V
os
Output connections
N 1
( ⁄ ) ×
–
D 2 G
DocID024597 Rev 3
Digital-to-analog converter (DAC)
× )
V V
+
ref OS
is the nominal full-
ref
= 0.
os
, a calibration
os
551/1693
573