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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
737
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MHz when driven from a 50 ohm source. The filter adds a parasitic capacitance of approximately 1.2
pF towards local VSS when enabled. The filter is enabled out of reset and can be disabled by setting
OPAxLPFDIS in DACn_OPAxCTRL.
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
OPA Configuration
OPAx POSSEL
POSPADx
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
bit-field to UG in the DACn_OPAxMUX register as shown in Figure 30.4 (p. 737) . 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
OPA Configuration
OPAx POSSEL
OPATAP, NEXTOUT, POSPADx
OPAx NEGSEL
UG
OPAx RESINMUX
DISABLE
Summary of Contents for Giant Gecko EFM32GG
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