AMIS-30621 Datasheet, PDF (32/59 Pages) AMI SEMICONDUCTOR – LIN Microstepping Motordriver

AMIS−30621
Motor Stopping Phase
At the end of the deceleration phase, the currents are
maintained in the coils at their actual DC level (hence
keeping the sine/cosine ratio between coils) during the
stabilization time t_stab (see AC Table). The currents are then
set to the hold values, respectively Ihold x
sin(TagPos) and Ihold x cos(TagPos), as
illustrated below. A new positioning order can then be
executed.
Iy
Ix
t
Figure 20. Motor Stopping Phase
t _stab
Charge Pump Monitoring
If the charge pump voltage is not sufficient for driving the
high side transistors (due to a failure), an internal
HardStop command is issued. This is acknowledged to
the master by raising flag <CPFail> (available with
command GetFullStatus).
In case this failure occurs while a motion is ongoing, the
flag <StepLoss> is also raised.
Electrical Defect on Coils, Detection and Confirmation
The principle relies on the detection of a voltage drop on
at least one transistor of the H−bridge. Then the decision is
taken to open the transistors of the defective bridge.
This allows the detection the following short circuits:
• External coil short circuit
• Short between one terminal of the coil and Vbat or
GND
• One cannot detect an internal short in the motor.
Open circuits are detected by 100% PWM duty cycle
value during one electrical period with duration, determined
by Vmin.
Table 22. ELECTRICAL DEFECT DETECTION
Pins
Fault mode
Yi or Xi
Short circuit to GND
Yi or Xi
Short circuit to Vbat
Yi or Xi
Open
Y1 and Y2
Short circuited
X1 and X2
Short circuited
Xi and Yi
Short circuited
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).
• The charge pump voltage goes below the charge pump
comparator level Flag <CPFail> = ‘1’, meaning there is
a charge pump failure.
• Flag <ElDef> = ‘1’, meaning an electrical problem is
detected on one or both coils, e.g. a short circuit.
A motor shutdown leads to the following:
• H−bridges in high impedance mode.
• The <TagPos> register is loaded with the
<ActPos>.
• The LIN 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 GetStatus or GetFullStatus
command AND
• The four above causes are no longer detected
This leads to H−bridges going 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 example. The master can check whether there is
a problem or not and decide which application strategy to
adopt.
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