AMIS-30521 Datasheet, PDF (18/28 Pages) AMI SEMICONDUCTOR – Micro-stepping Motor Driver

Ssh
V _COIL
div2
div4
AMIS−30521, NCV70521
Sh
Csh
buf
Ch
SLA−Pin
ICOIL = 0
PWMsh
PWMsh
ICOIL = 0
SLAT
VCOIL
SLAT
NOT (ICOIL = 0)
SLA−Pin
last sample
is retained
V _BEMF
t
retain last sample
SLAT = 1 => SLA−pin is transparent during
V_BEMF sampling @ coil current zero crossing.
SLA−pin is updated “real−time”.
previous output is kept at SLA pin
t
SLAT = 0 => SLA−pin is not “transparent” during
V_BEMF sampling @ coil current zero crossing.
SLA−pin is updated when leaving current−less state.
Figure 14. Timing Diagram of SLA−Pin
Warning, Error Detection and Diagnostics Feedback
Thermal Warning and Shutdown
When Junction temperature rises above T_TW, the thermal
warning bit <TW> is set (Table 15 SPI Status Register 0). If
junction temperature increases above thermal shutdown
level, then the circuit goes in “Thermal Shutdown” mode
(<TSD>) and all driver transistors are disabled (high
impedance) (Table 15 SPI Status Register 2). The
conditions to reset flag <TSD> is to be at a temperature
lower than T_TW and to clear the <TSD> flag by reading it
using any SPI read command.
Overcurrent Detection
The overcurrent detection circuit monitors the load
current in each activated output stage. If the load current
exceeds the overcurrent detection threshold, then the
overcurrent flag is set and the drivers are switched off to
reduce the power dissipation and to protect the integrated
circuit. Each driver transistor has an individual detection bit
in the Table 15 SPI status registers 1 and SPI Status Register
2 (<OVCXij> and <OVCYij>). Error condition is latched
and the microcontroller needs to clear the status bits to
reactivate the drivers.
Note: Successive reading the SPI Status Registers 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 32 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 15: SPI Status Register 0)
When the resistance of a motor coil is very large and the
battery 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 32 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.
http://onsemi.com
18