
Operational amplifiers (OPAMP)
RM0351
DocID024597 Rev 5
23.3.2 Initial
configuration
The default configuration of the operational amplifier is a functional mode where the three
IOs are connected to external pins. In the default mode the operational amplifier uses the
factory trimming values. See electrical characteristics section of the datasheet for factory
trimming conditions, usually the temperature is 30 °C and the voltage is 3 V. The trimming
values can be adjusted, see
for changing the trimming values.
The default configuration uses the normal mode, which provides the highest performance.
Bit OPALPM can be set in order to switch the operational amplifier to low-power mode and
reduced performance. Both normal and low-power mode characteristics are defined in the
section “electrical characteristics” of the datasheet. Before utilization, the bit OPA_RANGE
of OPAMP_CSR must be set to 1 if V
DDA
is above 2.4V, or kept at 0 otherwise.
As soon as the OPAEN bit in OPAMP_CSR register is set, the operational amplifier is
functional. The two input pins and the output pin are connected as defined in
and the default connection settings can be changed.
Note:
The inputs and output pins must be configured in analog mode (default state) in the
corresponding GPIOx_MODER register.
23.3.3 Signal
routing
The routing for the operational amplifier pins is determined by OPAMP_CSR register.
The connections of the two operational amplifiers (OPAMP1 and OPAMP2) are described in
the table below.
Table 147. Operational amplifier possible connections
Signal
Pin
Internal
comment
OPAMP1_VINM PA1 or dedicated pin
(1)
1. The dedicated pin is only available on BGA132 and BGA169 (for STM32L496xx/4A6xx devices) package.
This configuration provides the lowest input bias current (see datasheet).
OPAMP1_OUT
or PGA
controlled by bits OPAMODE
and VM_SEL.
OPAMP1_VINP
PA0
DAC1_OUT1
controlled by bit VP_SEL.
OPAMP1_VOUT PA3
ADC1_IN8
ADC2_IN8
The pin is connected when the
OPAMP is enabled. The ADC
input is controlled by ADC.
OPAMP2_VINM PA7 or dedicated pin
OPAMP2_OUT
or PGA
controlled by bits OPAMODE
and VM_SEL.
OPAMP2_VINP
PA6
DAC1_OUT2
controlled by bit VP_SEL
OPAMP2_VOUT PB0
ADC1_IN15
ADC2_IN15
The pin is connected when the
OPAMP is enabled. The ADC
input is controlled by ADC.