SAM L10/L11 Operational Amplifier Controller (OPAMP)

Operational Amplifier Controller (OPAMP)

Overview

The Operational Amplifier Controller (OPAMP) configures and controls three low power, general-purpose operational amplifiers offering a high degree of flexibility and rail-to-rail inputs. Most common inverting or non-inverting programmable gain and hysteresis configurations can be selected by software. No external components are required for these configurations. The OPAMPs can be cascaded for both standalone mode and built-in configurations. Each OPAMP can be used as a standalone amplifier. External pins are available for filter configurations or other applications.

A reference can be generated from the Digital-to-Analog Converter (DAC) to be used as a selectable reference for inverting Programmable Gain Amplifier (PGA) or instrumentation amplifier. Each OPAMP can be used as a buffer or PGA for the Analog-to-Digital Converter (ADC) or an Analog Comparator (AC). The OPAMP offset voltage can be compensated when it is used in combination with the ADC.

Four modes are available to select the trade-off between speed and power consumption to best fit the application requirements and optimize power consumption.

Features

  • Three individually configurable low power OPAMPs
  • Rail-to-rail inputs
  • Configurable resistor ladders for internal feedback
  • Selectable configurations
    • Standalone OPAMP with flexible inputs
    • Unity gain amplifier
    • Non-inverting / inverting Programmable Gain Amplifier (PGA)
    • Cascaded PGAs
    • Instrumentation amplifier
    • Comparator with programmable hysteresis
  • OPAMP output:
    • On I/O pins
    • As input for AC or ADC
  • Flexible input selection:
    • I/O pins
    • DAC
    • Ground
  • Low power options:
    • Selectable voltage doubler and propagation delay versus current consumption
    • On-demand start-up for ADC and AC operations
  • Offset/Gain measurement for calibration when used with the ADC

Block Diagram

saml10-opamp.png

Principle of Operation

Using the OPAMP I/O lines requires the I/O pins to be configured. Refer to the "PORT - IO Pin Controller" chapter in the device data sheet for details.

Each OPAMP has two I/O pins that can be used as analog inputs. These pins must be configured for analog operation before using them as OPAMP inputs. If the DAC is to be used as OPAMP input, the DAC must be configured and enabled first. Each OPAMP has one I/O pin that can be used as analog output. This pin must be configured for analog operation before using it as OPAMP output. The analog signals of AC, ADC, DAC, and OPAMP can be interconnected. The AC and ADC peripheral can request the OPAMP using an analog ONDEMAND functionality.

The OPAMP bus clock (CLK_OPAMP_APB) can be enabled and disabled in the Power Manager, and the default state of CLK_OPAMP_APB can be found in the Peripheral Clock Masking. A clock (CLK_ULP32K) is required by the voltage doubler for low voltage operation (VCC < 2.5V). The CLK_ULP32K is a 32 kHz clock which is provided by the OSCULP32K oscillator in the OSC32KCTRL module.

Each OPAMP has one positive and one negative input. Each input may be chosen from either a selection of analog input pins or internal inputs such as the DAC, the resistor ladder and the ground and output of another OPAMP. Each OPAMP can be configured with built-in feedback to support various functions with programmable or unity gain. The I/O pins are externally accessible so that the operational amplifier can be configured with external feedback. All OPAMPs can be cascaded to support circuits such as differential amplifiers.

Refer to the "OPAMP – Operational Amplifier Controller, Functional Description" from the product data sheet for more details.

Code Example:

This OPAMP application note illustrates how to configure the OPAMP.

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