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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
738
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30.3.2.3 Inverting input PGA
Figure 30.5 (p. 738) shows the inverting input PGA configuration. In this mode the negative
input is connected to the resistor ladder by setting the OPAxNEGSEL bit-field 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 bit-field in DACn_OPAxMUX. Signal
ground for the positive input can be generated off-chip through the pad by setting OPAxPOSSEL bit-
field to PAD in DACn_OPAxMUX. In addition the output is configured by the OUTPEN bit-field, located
in DACn_OPAxMUX.
Figure 30.5. Inverting input PGA Overview
VOUT
VOUT= - (VIN- POS) R2/ R1 + POS
R1
R2
POS
-
+
VIN
Table 30.3. Inverting input PGA Configuration
OPA bit-fields
OPA Configuration
OPAx POSSEL
POSPADx
OPAx NEGSEL
OPATAP
OPAx RESINMUX
NEXTOUT, NEGPADx, POSPADx
30.3.2.4 Non-inverting PGA
Figure 30.6 (p. 738) shows the non-inverting input configuration. In this mode the negative input is
connected to the resistor ladder by setting the OPAxNEGSEL bit-field to OPATAP in DACn_OPAxMUX.
This setting provides a programmable gain on the negative input, which can be set by choosing the
wanted gain value in the RESSEL bit-field in DACn_OPAxMUX. In addition the OPAxRESINMUX
bit-field must be set to VSS or NEGPAD in DACn_OPAxMUX. The positive input is selected by
the OPAxPOSSEL bit-field, and the output is configured by the OUTPEN bit-field, both located in
DACn_OPAxMUX.
Figure 30.6. Non-inverting PGA Overview
R1
R2
VIN
-
+
VOUT
VOUT= VIN(1+ R2/ R1)
Table 30.4. Non-inverting PGA Configuration
OPA bit-fields
OPA Configuration
OPAx POSSEL
NEXTOUT, POSPADx
OPAx NEGSEL
OPATAP
OPAx RESINMUX
VSS, NEGPAD
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