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AMIS-30624 I
2
C Microstepping Motordriver
Data Sheet
15.3.8. Motor Shutdown Mode
A motor shutdown occurs when:
The chip temperature rises above the thermal shutdown threshold Ttsd (see
Thermal Shutdown Mode
)
The battery voltage goes below UV2 (see
Battery Voltage Management
)
Flag <
ElDef
> = ‘1’, meaning an electrical problem is detected on one or both coils, e.g. a short circuit
Flag <
CPFail
> = ‘1’, meaning there is a charge pump failure
A motor shutdown leads to the following:
H-bridges in high impedance mode
The
TagPos
register is loaded with the
ActPos
(to avoid any motion after leaving the motor shutdown mode)
The I
2
C interface remains active, being able to receive orders or send status.
The conditions to get out of a motor shutdown mode are:
Reception of a
GetFullStatus1
command AND
The four causes above are no longer detected
This leads to H-bridges in Ihold mode, hence the circuit is ready to execute any positioning command.
This can be illustrated in the following sequence given as an application tip. The master can check whether there is a problem or not
and decide which application strategy to adopt.
Tj
≥
Tsd or
Vbb
≤
UV2 or
<
ElDef
> = ‘1’ or
<
CpFail
> = ‘1’
↓
↑
-
The application is
-
The circuit is driven in
motor shutdown
mode
-
The application is not
aware of this
mode
no motion
-
The application is still
unaware
SetPosition
frame
GetFullStatus1
frame
↑
GetFullStatus1
frame
↑
…
-
Possible confirmation
of the problem
aware of a problem
-
Reset <
TW
> or <
TSD
> or <
UV2
> or <
StepLoss
>
or <
ElDef
> or <
CPFail
> by the application
-
Possible new detection of over temperature or
low voltage or electrical problem
Circuit
sets <
TW
> or <
TSD
> or <
UV2
> or
<
StepLoss
> or <
ElDef
> or <
CPFail
>
again at ‘1’
-
The position set-point
is updated by the
I
C Master
-
Motor shutdown
Figure 21: Example of Possible Sequence Used to Detect and Determine Cause of Motor Shutdown
Important:
While in shutdown mode, since there is no hold current in the coils, the mechanical load can cause a step loss, which
cannot be flagged by the AMIS-30624.
Warning:
The application should limit the number of consecutive
GetFullStatus1
commands to try to get the AMIS-30624 out of
shutdown mode. When this proves to be unsuccessful, for example if there is a permanent defect, the reliability of the circuit could be
altered since
GetFullStatus1
attempts to disable the protection of the H-bridges.
36
AMI Semiconductor
– Apr. 2007, Rev 3.1, M-20664-003
www.amis.com