3 Atmel START

Atmel START comes with a driver for the OPAMP module allowing for easy configuration of the module. The Atmel START module comes with nine predefined configurations as well as a custom mode.

Figure 3-1. Atmel START Initial Configurations
At the top of the module, as seen in Figure   1, several global options that can be set for the module, such as enabling the module, enabling the module in debug mode, and selecting the input range. Under “Component Signals”, the input and output pins can be selected. Selecting the pins will turn off the digital input buffer for the pins. It is therefore recommended to select all used pins. The “Select OPAMP Combination” option is used to select which op amps are configured separately and which op amps are combined to create a multi op amp configuration. All op amps can be configured to any of the single op amp configurations, but some of the multi op amp configurations are only available using specific op amps. For an overview of possible combinations, see Table   1.
Table 3-1. Multi Op Amp Configurations
Op Amp CombinationsPosible Configurations
OP1-OP2Differential Amplifier, Cascaded (Two) Non-Inverting PGA, Cascading (Two) Inverting PGA
OP2-OP1Differential Amplifier, Cascaded (Two) Non-Inverting PGA, Cascading (Tow) Inverting PGA
OP2-OP0Differential Amplifier, Cascading (Two) Inverting PGA
OP0-OP1-OP2Instrumentation Amplifier, Cascaded (Three) Non-Inverting PGA, Cascaded (Three) Inverting PGA
OP1-OP2-OP0Instrumentation Amplifier, Cascaded (Three) Inverting PGA
OP2-OP0-OP1Instrumentation Amplifier, Cascaded (Three) Inverting PGA

After selecting the global options for the OPAMP module, the settings for the individual op amps can be set. The first option is to select which configuration is desired. For each configuration, there is an accompanying picture to show how the configuration looks. The OPAMPn settings will have different fields grayed out depending on the configurations. The grayed-out field cannot be changed as that would break the configuration, but they are visible to show how the op amp is configured. The other field can be changed as normal and typically change the input or the gain of the configuration.

Figure 3-2. Atmel START Op Amp Configuration

The last options ("HARDWARE SETTINGS") are hardware-specific to each op amp. By default, they are configured as always on and in normal output mode. This way, the op amp works as soon as it is initialized. The settle time is set to the maximum, as this is the srecommended value for an unknown load.