User manual

...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 729
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OPA bitfields OPA Configuration
OPAx NEGSEL OPATAP, UG, NEGPADx
OPAx RESINMUX NEXTOUT, POSPADx, NEGPADx VSS
30.3.2.2 Voltage Follower Unity Gain
In this mode the unity gain feedback path is selected for the negative input by setting the OPAxNEGSEL
bitfield to UG in the DACn_OPAxMUX register as shown in Figure 30.3 (p. 729) . The positive input
is selected by the OPAxPOSSEL bitfield, and the output is configured by the OUTPEN bitfield, both in
the DACn_OPAxMUX register.
Figure 30.3. Voltage Follower Unity Gain Overview
VIN
-
+
VOUT
Table 30.2. Voltage Follower Unity Gain Configuration
OPA bitfields OPA Configuration
OPAx POSSEL OPATAP, NEXTOUT, POSPADx, DACx
OPAx NEGSEL UG
OPAx RESINMUX DISABLE
30.3.2.3 Inverting input PGA
Figure 30.4 (p. 729) shows the inverting input PGA configuration. In this mode the negative
input is connected to the resistor ladder by setting the OPAxNEGSEL bitfield to OPATAP in the
DACn_OPAxMUX register. This setting provides a programmable gain on the negative input, which
can be set by choosing the wanted gain value in the RESSEL bitfield in DACn_OPAxMUX. Signal
ground for the positive input can be generated off-chip through the pad by setting OPAxPOSSEL bitfield
to PAD in DACn_OPAxMUX. In addition the output is configured by the OUTPEN bitfield, located in
DACn_OPAxMUX.
Figure 30.4. Inverting input PGA Overview
VOUT
VOUT= -(VIN-POS) R2/R1 + POS
R1
R2
POS
-
+
VIN
Table 30.3. Inverting input PGA Configuration
OPA bitfields OPA Configuration
OPAx POSSEL POSPADx
OPAx NEGSEL OPATAP
OPAx RESINMUX NEXTOUT, NEGPADx, POSPADx