EFM32WG Datasheet, PDF (729/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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30.3.1.7 Disabling of rail-to-rail Operation
Each opamp can have the input rail-to-rail stage disabled by setting the OPAxHCMDIS bit-field in
DACn_OPACTRL. Disabling the rail-to-rail input stage improves linearity of the opamp, thus improving
the Total Harmonic Distortion, THD, at the cost of reduced input signal swing.
30.3.2 Opamp Modes
The opamp can be configured to perform different Operational Amplifier functions by configuring the
internal signal routing between the opamps. The modes available are described in the following sections.
30.3.2.1 General Opamp Mode
In this mode the resistor ladder is isolated from the feedback path and input signal routing is defined
by OPAxPOSSEL and OPAxNEGSEL in DACn_OPAxMUX. The output signal routing is defined by
OUTPEN in DACn_OPAxMUX
Table 30.1. General Opamp Mode Configuration
OPA bit-fields
OPAx POSSEL
OPAx NEGSEL
OPAx RESINMUX
OPA Configuration
POSPADx
OPATAP, UG, NEGPADx
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
bit-field to UG in the DACn_OPAxMUX register as shown in Figure 30.4 (p. 729) . The positive input
is selected by the OPAxPOSSEL bit-field, and the output is configured by the OUTPEN bit-field, both
in the DACn_OPAxMUX register.
Figure 30.4. Voltage Follower Unity Gain Overview
VIN ₊
-
VOUT
Table 30.2. Voltage Follower Unity Gain Configuration
OPA bit-fields
OPAx POSSEL
OPAx NEGSEL
OPAx RESINMUX
OPA Configuration
OPATAP, NEXTOUT, POSPADx
UG
DISABLE
30.3.2.3 Inverting input PGA
Figure 30.5 (p. 730) 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-
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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