Operation
64
Atlas® Digital Amplifier Complete Technical Reference
4
In this example the continuous current limit would be set to 3 amps, and the energy limit would be set to:
Energy Limit = (peak current
2
- continuous current limit
2
) * time
Energy Limit = (5A
2
- 3A
2
) * 2 Sec
Energy Limit = 32A
2
Sec
4.8.9.3
Current Foldback Event Processing
Atlas provides a programmable mechanism related to the current foldback condition. This can be useful for tailoring
the response of the Atlas to best suit a specific application.
The Atlas facility that handles this type of programmable response is called an event. Events allow event actions to be
executed automatically once a specified condition occurs. In this case, the event condition is satisfied if Atlas is in a
current foldback condition, and the following table describes the event actions that can be selected by the external
controller:
The command
SetEventAction
is used to specify both the condition and the action that should be taken. The external
controller must specify that the condition is “current foldback,” and also specify one of the two conditions from the
table above. Upon occurrence, the programmed action is executed along with any related actions, such as setting the
appropriate bit in the Event Status register.
To recover from an event action the command
RestoreOperatingMode
is used. This command will reset Atlas to
the operating mode previously specified using
SetOperatingMode
command. Note that if the event condition is still
present, the event action will immediately occur again.
Once programmed, an event action will be in place until reprogrammed. The occurrence of the event condition does
not reset the programmed event action.
The default action for the current foldback event is to disable the power stage and current loop.
4.9
Step Motor Control
While many aspects of Atlas operation are similar between step motors and Brushless DC or DC Brush motors, Atlas
provides a number of special features for supporting step motors. This section describes these special step motor-
specific features.
Current foldback, when it occurs, may indicate a serious condition affecting motion stability, smoothness, and per-
formance. It is the responsibility of the user to determine the appropriate response to a current foldback event.
Action Name
Description
No Action
No event-related action taken, current limited to continuous
current limit
Disable power stage and current loop
Disables the power stage and the current loop module
If a foldback event occurs when Atlas is in voltage mode (current loop not enabled), then the power stage will be
disabled regardless of the setting of the event action.
