st,stm32g4-opamp

Description

STM32G4 OPAMP (Operational Amplifier)

One OPAMP has two inputs and one output. The three I/Os can be connected
to the external pins, enabling any type of external interconnection.
An OPAMP can be configured internally:
  - standalone amplifier (external gain setting mode)
  - follower
  - non-inverting amplifier with gains ranging from 2 to 64
  - inverting amplifier with gains ranging from -1 to -63

The positive input (INP) can be connected to the internal DAC.
The output (VOUT) can be connected to the internal ADC.

Main features:
  - Rail-to-rail input voltage range
  - Low input bias current
  - Low input offset voltage
  - High frequency gain bandwidth
  - High-speed mode to achieve a better slew rate
  - Self calibration support for better offset voltage adjustment
    of the input NMOS and PMOS transistors

Minimal DTS examples for OPAMP2:

  - Standalone amplifier (external gain):
    ```
    &opamp2 {
      pinctrl-0 = <&opamp2_vinm_pa5 &opamp2_vinp_pa7 &opamp2_vout_pa6>;
      pinctrl-names = "default";
      functional-mode = "standalone";
      inp = "VINP0";
      status = "okay";
    };
    ```
    NOTES: Following points regarding standalone mode are to be considered:
      - inm is tied to VINM0 independently of the value provided in DTS

  - Follower (voltage buffer):
    ```
    &opamp2 {
      pinctrl-0 = <&opamp2_vout_pa6>;
      pinctrl-names = "default";
      functional-mode = "follower";
      inp = "DAC";
      status = "okay";
    };
    ```

  - Non-inverting PGA (gain 2..64):
    ```
    &opamp2 {
      pinctrl-0 = <&opamp2_vinp_pb14 &opamp2_vout_pa6>;
      pinctrl-names = "default";
      functional-mode = "non_inverting";
      inp = "VINP1";
      status = "okay";
    };
    ```

  - Inverting PGA (gain -1..-63):
    ```
    &opamp2 {
      pinctrl-0 = <&opamp2_vinm_pc5 &opamp2_vinp_pb0
                   &opamp2_vout_pa6>;
      pinctrl-names = "default";
      functional-mode = "inverting";
      inp = "VINP2"; /* shall be routed to external bias voltage */
      inm = "VINM0"; /* VINM0 is only allowed choice */
      status = "okay";
    };
    ```

Timer-controlled input MUX (non-inverting PGA):
  - Switch between VINP0 and VINP3 on TIM1_CH6 trigger.
  ```
  &opamp2 {
    pinctrl-0 = <&opamp2_vinm_pa5 &opamp2_vinm_pc5
                 &opamp2_vinp_pa7 &opamp2_vout_pa6>;
    pinctrl-names = "default";
    functional-mode = "standalone";
    st,inputs-mux-mode = "TIM1_CH6";
    inp = "VINP0", "VINP3";
    status = "okay";
  };
  ```

Usage with an ADC:
  ```
  / {
      zephyr,user {
        opamp = <&opamp2>;
      };
    };

    &adc2 {
      st,adc-clock-source = "SYNC";
      st,adc-prescaler = <4>;
      status = "okay";

      #address-cells = <1>;
      #size-cells = <0>;

      channel@3 {
        reg = <3>;
        zephyr,gain = "ADC_GAIN_1";
        zephyr,reference = "ADC_REF_INTERNAL";
        zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
        zephyr,resolution = <12>;
        zephyr,vref-mv = <3300>;
      };
    };

    &opamp2 {
      pinctrl-0 = <&opamp2_vinm_pa5 &opamp2_vinp_pa7>;
      pinctrl-names = "default";
      functional-mode = "non_inverting";
      inm = "VINM0";
      inp = "VINP0";
      io-channels = <&adc2 3>;
      status = "okay";
    };
    ```
  NOTE: ADC can be read from the code with usual ADC API.

NOTE: It is highly recommended to take a look at RM0440 Rev 9 and AN5306
      for more details about STM32G4 OPAMP features and usage.

References:
  - AN5306:
    https://www.st.com/resource/en/application_note/an5306-operational-amplifier-opamp-usage-in-stm32g4-series-stmicroelectronics.pdf
  - RM0440 Rev 9:
    https://www.st.com/content/ccc/resource/technical/document/reference_manual/group0/7c/b0/25/29/1b/a2/42/b2/DM00355726/files/DM00355726.pdf/jcr:content/translations/en.DM00355726.pdf

Properties

Properties not inherited from the base binding file.

Name

Type

Details

st,power-mode

string

 
OPAMP power mode has impact on slew-rate:
  - NORMAL - slew-rate 6.5 V/µs with low power consumption.
  - HIGHSPEED - slew-rate 45 V/µs with higher power consumption.
source: https://www.st.com/resource/en/product_training/STM32G4-Analog-OPAMP_OPAMP.pdf

Default value: NORMAL

Legal values: NORMAL, HIGHSPEED

st,lock-enable

boolean

 
Lock the OPAMP configuration after it has been configured by the driver.
Resetting the lock mode can only be done by a system reset.
If not set, the OPAMP configuration will be unlocked by default.
The lock property is used to prevent accidental changes to the OPAMP
configuration after it has been set.
NOTES:
  - In st,inputs-mux-mode the timer mux register will be locked too

st,enable-self-calibration

boolean

 
Enable self-calibration mode.
If not set, the self-calibration mode will be disabled by default.
The self-calibration mode is used to calibrate the OPAMP for optimal
performance.
NOTES:
  - This step will be executed at OPAMP initialization

inp

string-array

 
Non-Inverting input selection.
Please refer to RM0440 Rev 9, Table 204. pp. 777/2140 for more details.
NOTES:
  - Selecting st,inputs-mux-mode expects secondary input entry too

This property is required.

Legal values: VINP0, VINP1, VINP2, VINP3, DAC

inm

string-array

 
Inverting input selection.
Please refer to RM0440 Rev 9, Table 204. pp. 777/2140 for more details.
NOTES:
  - In case st,inputs-mux-mode is selected:
    * In standalone mode muxed between VINM0 and VINM1 (VM_SEL = '00' or '01')
    * In inverting/non_inverting (VM_SEL = '10') or follower (VM_SEL = '11') mode
      muxed between resistor feedback and VOUT.
      Basically, multiplexing happens between PGA and follower modes.
      ATTENTION: No VINM0/VINM1 multiplexing happens here!
  - The values in the array shall be ordered (e.g. VINM0, VINM1)

Legal values: VINM0, VINM1

st,inm-filtering

string

 
Inverting input filtering selection.
Please refer to RM0440 Rev 9 pp. 783-784/2140 for more details.
NOTES:
  - Only applicable in inverting/non_inverting PGA modes

Default value: NONE

Legal values: NONE, VINM0, VINM1

st,inputs-mux-mode

string

 
Timer controlled multiplexer mode.
The selection of the OPAMP inverting and non inverting inputs can be done automatically. In
this case, the switch from one input to another is done automatically. This automatic switch
is triggered by the TIM1 CC6 or TIM8 CC6 or TIM20 CC6 output arriving on the OPAMP
input multiplexers.
This is useful for dual motor control with a need to measure the currents on the 3 phases
simultaneously on a first motor and then on the second motor.
Please refer to RM0440 Rev 9, 25.3.8 Timer controlled Multiplexer mode, pp. 786/2140

Default value: DISABLE

Legal values: DISABLE, TIM1_CH6, TIM8_CH6, TIM20_CH6

st,pmos-trimming-value

int

 
OPAMP PMOS transistor offset trimming value.
The value will be applied directly to TRIMOFFSETP[4:0] (Bits 23:19 in OPAMPx_CST register).
If value is present and self-calibration is enabled, this value will overwrite values
calculated during self-calibration.
Please refer to RM0440 Rev 9, pp. 789/2140 for more details.
NOTE: Acceptable range is 0x00 to 0x1f.

st,nmos-trimming-value

int

 
OPAMP NMOS transistor offset trimming value.
The value will be applied directly to TRIMOFFSETN[4:0] (Bits 28:24 in OPAMPx_CST register).
If value is present and self-calibration is enabled, this value will overwrite values
calculated during self-calibration.
Please refer to RM0440 Rev 9, pp. 789/2140 for more details.
NOTE: Acceptable range is 0x00 to 0x1f.

pinctrl-0

phandles

 
Pin configuration/s for the first state. Content is specific to the
selected pin controller driver implementation.

This property is required.

pinctrl-names

string-array

 
Names for the provided states. The number of names needs to match the
number of states.

This property is required.

functional-mode

string

 
Selects opamp functional mode.

a) differential mode

- Signals applied to both inputs
- Amplifies the difference between two input signals
- Common-mode signals are rejected
- Used in instrumentation and noise rejection
- Vout = (Rf/Rin) * (Vin2 - Vin1), where Rf is the feedback resistor
  and Rin is the input resistor, with gain (Rf/Rin)

         Rin        Rf
Vin1 --/\/\/\--*--/\/\/\-----
               |            |
               |     |\     |
               ------|- \   |
                     |   >--*-- Vout
               ------|+ /
               |     |/
               |
Vin2 --/\/\/\--*--/\/\/\-----
         Rin        Rf      |
                           GND

b) inverting mode

- Input signal applied to inverting (-) terminal
- Non-inverting (+) terminal connected to ground
- Feedback resistor connects output to inverting input
- Output is 180° out of phase with input
- Vout = (-Rf/Rin) * Vin, where Rf is the feedback resistor
  and Rin is the input resistor, s.t. gain is (-Rf/Rin)

        Rin        Rf
Vin --/\/\/\--*--/\/\/\-----
              |            |
              |     |\     |
              ------|- \   |
                    |   >--*-- Vout
              ------|+ /
              |     |/
            GND

c) non_inverting mode

- Input signal applied to non-inverting (+) terminal
- Inverting (-) terminal connected to feedback network
- Output is in phase with input
- Vout = (1 + (Rf/Rin)) * Vin, where Rf is the feedback resistor
  and Rin is the input resistor, s.t. gain is (1 + (Rf/Rin))

      Rin        Rf
 |--/\/\/\--*--/\/\/\-----
 |          |            |
GND         |     |\     |
            ------|- \   |
                  |   >--*-- Vout
        Vin ------|+ /
                  |/

d) follower mode (voltage follower or buffer)

- Special case of non-inverting amplifier
- Vout = 1 * Vin, s.t. gain is 1
- Direct feedback from output to inverting input
- Very high input impedance, very low output impedance
- Used for impedance matching

    --------------
    |            |
    |     |\     |
    ------|- \   |
          |   >--*-- Vout
Vin ------|+ /
          |/

e) standalone mode

- The opamp mode is defined by external circuitry

          |\
Vin- -----|- \
          |   >---- Vout
Vin+ -----|+ /
          |/

References:
  - https://www.electronics-tutorials.ws/category/opamp

This property is required.

Legal values: differential, inverting, non_inverting, follower, standalone

programmable-gain

string-array

 
If the OPAMP supports programmable gain, then the gain of
the opamp can be changed dynamically at runtime. The gain
value needs to be one of the enumerations above.
Gain selection:
- OPAMP_GAIN_1_7  : x 1/7
- OPAMP_GAIN_1_3  : x 1/3
- OPAMP_GAIN_1    : x 1
- OPAMP_GAIN_5_3  : x 5/3
- OPAMP_GAIN_2    : x 2
- OPAMP_GAIN_11_5 : x 11/5
- OPAMP_GAIN_3    : x 3
- OPAMP_GAIN_4    : x 4
- OPAMP_GAIN_13_3 : x 13/3
- OPAMP_GAIN_7    : x 7
- OPAMP_GAIN_8    : x 8
- OPAMP_GAIN_15   : x 15
- OPAMP_GAIN_16   : x 16
- OPAMP_GAIN_31   : x 31
- OPAMP_GAIN_32   : x 32
- OPAMP_GAIN_33   : x 33
- OPAMP_GAIN_63   : x 63
- OPAMP_GAIN_64   : x 64

Legal values: OPAMP_GAIN_1_7, OPAMP_GAIN_1_3, OPAMP_GAIN_1, OPAMP_GAIN_5_3, OPAMP_GAIN_2, OPAMP_GAIN_11_5, OPAMP_GAIN_3, OPAMP_GAIN_4, OPAMP_GAIN_13_3, OPAMP_GAIN_7, OPAMP_GAIN_8, OPAMP_GAIN_15, OPAMP_GAIN_16, OPAMP_GAIN_31, OPAMP_GAIN_32, OPAMP_GAIN_33, OPAMP_GAIN_63, OPAMP_GAIN_64

pinctrl-1

phandles

 
Pin configuration/s for the second state. See pinctrl-0.

pinctrl-2

phandles

 
Pin configuration/s for the third state. See pinctrl-0.

pinctrl-3

phandles

 
Pin configuration/s for the fourth state. See pinctrl-0.

pinctrl-4

phandles

 
Pin configuration/s for the fifth state. See pinctrl-0.