AMIS-30521 Datasheet, PDF (14/26 Pages) AMI SEMICONDUCTOR – Micro-stepping Motor Driver

AMIS-30521 Micro-stepping Motor Driver
Data Sheet
The following drawing illustrates the operation of the SLA-pin and the transparency-bit. "PWMsh" and "Icoil=0" are internal signals that
define together with SLAT the sampling and hold moments of the coil voltage.
V_COIL
div2
div4
Ssh
Sh
Csh
buf
Ch
SLA-pin
Icoil=0
PWMsh
PWMsh
Icoil=0
SLAT
V_COIL
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.
PC20070604.8
Figure 13: Timing Diagram of SLA-pin
8.6 Warning, Error Detection and Diagnostics Feedback
8.6.1. Thermal Warning and Shutdown
When junction temperature rises above T_TW, the thermal warning bit <TW> is set (Table 27: 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 29: 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.
8.6.2. Over-Current Detection
The over-current detection circuit monitors the load current in each activated output stage. If the load current exceeds the over-current
detection threshold, then the over-current 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 28: SPI Status Register 1 and Table 29: SPI Status
Register 2 (<OVCXij> and <OVCYij>). Error condition is latched and the microcontroller needs to clean the status bits to reactivate
the drivers.
AMI Semiconductor – June 2007, M-20683-001
14
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