ST STM32L4x6 User Manual

Operational amplifiers (OPAMP) RM0351
596/1693 DocID024597 Rev 3
Calibration procedure
Here are the steps to perform a full calibration of either one of the operational amplifiers:
1. Select correct OPA_RANGE in OPAMP_CSR, then set the OPAEN bit in OPAMP_CSR
to 1 to enable the operational amplifier.
2. Set the USERTRIM bit in the OPAMP_CSR register to 1.
3. Choose a calibration mode (refer to Table 117: Operating modes and calibration). The
steps 3 to 4 will have to be repeated 4 times. For the first iteration select
– Normal mode, offset cal high (N differential pair)
The above calibration mode correspond to OPALPM=0 and CALSEL=0 in the
OPAMP_CSR register.
4. Increment TRIMOFFSETN[4:0] in OPAMP_OTR starting from 00000b until CALOUT
changes to 1 in OPAMP_CSR.
Note: CALOUT will switch from 0 to 1 for offset cal high and from 1 to 0 for offset cal low.
Note: Between the write to the OPAMP_OTR register and the read of the CALOUT value, make
sure to wait for the t
OFFTRIM
max delay specified in the electrical characteristics section of
the datasheet, to get the correct CALOUT value.
The commutation means that the offset is correctly compensated and that the
corresponding trim code must be saved in the OPAMP_OTR register.
Repeat steps 3 to 4 for:
– Normal_mode and offset cal low
– Low power mode and offset cal high
– Low power mode and offset cal low
If a mode is not used it is not necessary to perform the corresponding calibration.
All operational amplifier can be calibrated at the same time.
Note: During the whole calibration phase the external connection of the operational amplifier
output must not pull up or down currents higher than 500 µA.
During the calibration procedure, it is necessary to set up OPAMODE bits as 00 or 01 (PGA
disable) or 11 (internal follower).
20.4 OPAMP low-power modes
Table 118. Effect of low-power modes on the OPAMP
Mode Description
Sleep No effect.
Low-power run No effect.
Low-power sleep No effect.
Stop 0 / Stop 1 No effect, OPAMP registers content is kept.
Stop 2
OPAMP registers content is kept. OPAMP must be disabled before entering
Stop 2 mode.

ST STM32L4x6 Specifications

General

Brand	ST
Model	STM32L4x6
Category	Microcontrollers
Language	English