Operation
62
Atlas® Digital Amplifier Complete Technical Reference
4
To clear the bits in this register the command
ClearDriveFaultStatus
is used.
4.8.8
FaultOut Signal
The Atlas unit’s
FaultOut
signal is used to indicate an occurrence of one or more drive faults. This signal is active high,
meaning it is high when a fault has occurred, and it is low when a fault has not occurred.
The
FaultOut
signal is programmable, so that the user may determine what fault states result in the
FaultOut
signal
becoming active. In particular, any bit condition of the Drive Fault Status register may be used to trigger activation of
the
FaultOut
signal. This is done using the command
SetFaultOutMask
. The value set using this command can be read
back using
GetFaultOutMask
. See
Section 4.8.7, “Drive Fault Status Register”
for more information on the Drive
Fault Status register
The bit mask specified using this command is ANDed with the Drive Fault Status register. If the result is non-zero,
the
FaultOut
signal is driven active. For example if a watchdog timeout has occurred (bit 4 of the Drive Fault Status
register and the mask has been set to a value of 0x10 (hexadecimal notation, equivalent to decimal value of 16)
FaultOut
will be active.
The default value for the fault out mask is 0x71, indicating that
FaultOut
will go active whenever an overcurrent,
overvoltage, undervoltage, or watchdog timeout event occurs.
4.8.9
Current Foldback
Current foldback, also known as I
2
t foldback, is a general purpose tool to protect the drive output stage or the motor
from excessive current.
I
2
t current foldback works by integrating, over time, the difference of the square of the actual motor current and the
square of a user-settable continuous current limit. When the integrated value reaches a user-settable energy limit, Atlas
goes into current foldback. The default response to this event is to cause the current loop and power stage modules
to be disabled. However it is also possible to program Atlas to attempt to clamp the maximum current to the
continuous current limit value. Note that the Atlas unit’s ability to do so depends on a properly functioning current
loop.
Atlas will stay in foldback until the integrator returns to zero. This is shown in
5
Overvoltage
Set 1 to indicate an overvoltage event in the supply bus volt-
age.
6
Undervoltage
Set 1 to indicate an undervoltage event in the supply bus volt-
age.
7
Disabled
Set 1 to indicate Enable signal was not asserted
8-11
Reserved
May contain 0 or 1
12
Current foldback
Set 1 to indicate a current foldback event
13-15
Reserved
May contain 0 or 1
Bit
Name
Description
