AMIS-30523 Datasheet, PDF (25/35 Pages) ON Semiconductor – CAN Micro-Stepping Motor Driver

AMIS−30523
Note: Successive reading the SPI StatusRegisters 1 and 2 in
case of a short circuit condition, may lead to damage to the
drivers
Open Coil/Current Not Reached Detection
Open coil detection is based on the observation of 100%
duty cycle of the PWM regulator. If in a coil 100% duty cycle
is detected for longer than 200 ms then the related driver
transistors are disabled (high−impedance) and an
appropriate bit in the SPI status register is set (<OPENX> or
<OPENY>). (Table 17 SPI Status Register Address SR0)
When the resistance of a motor coil is very large and the
supply voltage is low, it can happen that the motor driver is
not able to deliver the requested current to the motor. Under
these conditions the PWM controller duty cycle will be
100% and after 200 ms the error pin and <OPENX>,
<OPENY> will flag this situation (motor current is kept
alive). This feature can be used to test if the operating
conditions (supply voltage, motor coil resistance) still allow
reaching the requested coil−current or else the coil current
should be reduced.
Charge Pump Failure
The charge pump is an important circuit that guarantees
low R_DS(on) for all drivers, especially for low supply
voltages. If supply voltage is too low or external components
are not properly connected to guarantee R_DS(on) of the
drivers, then the bit <CPFAIL> is set in Table 17. Also after
POR the charge pump voltage will need some time to exceed
VBB
the required threshold. During that time t_CPU <CPFAIL>
will be set to “1”.
Error Output
This is a digital output to flag a problem to the external
microcontroller. The signal on this output is active low and
the logic combination of:
NOT(ERRB) = <TW> OR <TSD> OR <OVCXij> OR
< OVCYij> OR <OPENi> OR <CPFAIL>
This open drain output can be wired OR−ed with error
outputs other motor drivers.
Logic Supply Regulator
AMIS−30523 has an on−chip 5 V low−drop regulator
with external capacitor to supply the digital part of the chip,
some low−voltage analog blocks and external circuitry. The
voltage level is derived from an internal bandgap reference.
To calculate the available drive−current for external
circuitry, the specified I_load should be reduced with the
consumption of internal circuitry (unloaded outputs) and the
loads connected to logic outputs. See Table 5 DC parameters
Motor Driver.
Power−On Reset (POR) Function
The open drain output pin PORB/WD provides an “active
low” reset for external purposes. At power−up of
AMIS−30523, this pin will be kept low for some time to reset
for example an external microcontroller. A small analogue
filter avoids resetting due to spikes or noise on the V_DD
supply.
VDD
t_PU
t
t_PD
V_DDH
V_DDL
t
< t_RF
POR/WD pin
t_POR
t_RF
Figure 22. Power−on−Reset Timing Diagram
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