AMIS-30624_13 Datasheet, PDF (34/52 Pages) ON Semiconductor – I2C Micro-stepping Motor Driver

AMIS−30624, NCV70624
This can be illustrated in the following sequence given as an application example. The master can check whether there is
a problem or not and decide which application strategy to adopt.
Table 25. Example of Possible Sequence used to Detect and Determine Cause of Motor Shutdown
Tj  Tsd or
V_BB  UV2 (>15s) or
<ElDef> = ‘1’ or
<CPFail> = ‘1’ (>15s)

SetPosition
frame

GetFullStatus1 frame

GetFullStatus1 frame
...
− The circuit is driven in motor shutdown
mode
− The application is not aware of this
− The position set−point is
updated by the I²C Master
− Motor shutdown mode
 no motion
− The application is still
unaware
− The application is aware − Possible confirmation of
of a problem
the 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’
Important: While in shutdown mode, since there is no hold
current in the coils, the mechanical load can cause a step loss,
which indeed cannot be flagged by the
AMIS−30624/NCV70624.
Note: The Priority Encoder is describing the management of
states and commands.
Warning: The application should limit the number of
consecutive GetFullStatus1 commands to try to get the
AMIS−30624/NCV70624 out of shutdown mode when this
proves to be unsuccessful, e.g. there is a permanent defect.
The reliability of the circuit could be altered since
GetFullStatus1 attempts to disable the protection of the
H−bridges.
Motion Detection
Motion detection is based on the back emf generated
internally in the running motor. When the motor is blocked,
e.g. when it hits the end−stop, the velocity and as a result also
the generated back emf, is disturbed. The
AMIS−30624/NCV70624 senses the back emf, calculates a
moving average and compares the value with two
independent threshold levels: Absolute threshold
(AbsThr[3:0]) and Delta threshold (<DelThr[3:0]>).
Instructions for correct use of these two levels in
combination with three additional parameters
(<MinSamples>, <FS2StallEn> and <DC100StEn>)
are available in a dedicated Application Note “Robust
Motion Control with AMIS−3062x Stepper Motor Drivers”.
If the motor is accelerated by a pulling or propelling force
and the resulting back emf increases above the Delta
threshold (+DTHR), then <DelStallHi> is set. When the
motor is slowing down and the resulting back emf decreases
below the Delta threshold (−DTHR), then <DelStallLo>
is set. When the motor is blocked and the velocity is zero
after the acceleration phase, the back emf is low or zero.
When this value is below the Absolute threshold,
<AbsStall> is set. The <Stall> flag is the OR function
of <DelStallLo> OR <DelStallHi> OR
<AbsStall>.
Velocity
V_max
Vbemf
+DTHR
V_min
Vbemf
VABSTH
AbsStall
Motor speed
Back emf
V_bemf
t
DeltaStallHi
t
DeltaStallLo
V_bemf
−DTHR
t
t
t
t
Figure 20. Triggering of the Stall Flags in Function of Measured Backemf and the Set Threshold Levels
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