Operational Amplifier And Comparator; Operational Amplifier; Comparator; Table 13. Configuration Elements Related To Opamp1 - ST STM32L4R9I User Manual

UM2248
6.18

Operational amplifier and comparator

6.18.1

Operational amplifier

STM32L4R9AII6 provides two onboard operational amplifiers, one of which, OpAmp1, is
made accessible on STM32L4R9I-EVAL. OpAmp1 has its inputs and its output routed to I/O
ports PA0, PA1, and PA3, respectively. The noninverting input PA0 is accessible on terminal
1 of the jumper header (JP5). On top of the possibility of routing either the potentiometer or
LDR to PA0, an external source is also connectable to it, using terminal 1 of JP5.
The PA3 output of the operational amplifier is accessible on test point TP9. Refer to the
schematic
The ratio of the variable resistor RV1 and the resistor R246 determines the OpAmp1 gain,
as shown in the following equation:
Gain = 1 + RV1 / R246
With the RV1 ranging from 0 to 10 kΩ and R246 being 1 kΩ, the gain varies from 1 to 11.
The R108 resistor in series with PA0 is beneficial for reducing the output offset.
Table 13
OpAmp1 function.
Element
SB39
SB38
R214
R216
SB40
R215
R221
6.18.2

Comparator

STM32L4R9AII6 provides two on-board comparators, one of which, Comp2, is made
accessible on STM32L4R9I-EVAL. Comp2 has its noninverting input and its output routed to
diagram.
shows the configuration elements and their settings allowing them to access the

Table 13. Configuration elements related to OpAmp1

Setting
SB38 OFF
SB39 ON
R214 OFF
SB38 OFF
SB39 ON
R214 ON
SB38 ON
SB39 OFF
R214 OFF
R216 ON
SB40 OFF
R216 OFF
SB40 ON
R215 ON
R221 OFF
R215 OFF
R221 ON
OpAmp1_INP is routed to pin PA0 of STM32L4R9AII6.
Default setting: PA0 port of STM32L4R9AII6 is routed to
MFX_IRQ_OUT or motor control signal.
PA0 port of STM32L4R9AII6 is routed to the motor-control signal.
Default setting: OpAmp1_INM is routed to pin PA1 of
STM32L4R9AII6.
PA1 port of STM32L4R9AII6 is routed to the motor-control signal.
OpAmp1_VOUT is routed to pin PA3 of STM32L4R9AII6.
Default setting: OpAmp1_VOUT is not routed to pin PA3 of
STM32L4R9AII6. PA3 port of STM32L4R9AII6 is routed to
OCTOSPI1_CLK.
UM2248 Rev 5
Hardware layout and configuration
Configuration
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