AMIS-30624 Datasheet, PDF (20/56 Pages) AMI SEMICONDUCTOR – I2C Microstepping Motordriver

AMIS-30624
R2VBAT
A resistor is connected between VBAT and HW. Every 1024μs S_BOT is closed for a period of 128μs and a current is sensed. The output
of the I Æ R converter is low and the HW_Cmp output is high. Assuming the previous state was floating, the internal LOGIC will
interpret this as a change of state and the new state will be High (see also Table 15). The next time S_BOT is closed the same condition is
observed. The previous state was high, so based on Table 15 the new state remains unchanged. This high state will be interpreted as
HW address = 1.
OPEN
In case the HW connection is lost (broken wire, bad contact in connector) the next time S_BOT is closed this will be sensed. There will be
no current, the output of the corresponding I Æ R converter is high and the HW_Cmp will be low. The previous state was High. Based
on Table 15 one can see that the state changes to float. This will trigger a motion to secure position after a debounce time of 64 ms.
This prevents false triggering in case of micro interruptions of the power supply. See also Electrical Transient Conduction Along Supply
Lines.
R2GND
If a resistor is connected between HW and the GND, a current is sensed every 1024μs when S_TOP is closed. The output of the top I Æ
R converter is low and as a result the HW_Cmp output switches to high. Again based on the stated diagram in Table 15 one can see
that the state will change to low. This low state will be interpreted as HW address = 0.
14.1.5. External Switch SWI
As illustrated in Figure 12, the SWI comparator is almost identical to HW. The major difference is in the limited number of states. Only
open or closed is recognised leading to respectively ESW = 0 and ESW = 1.
IÎ R
S_{PASS_T}
SWI S_TOP
S_BOT
DriveHS
DriveLS
LOGIC
State
Closed
Open
1 = R2GND 2 = R2VBAT 3 = OPEN
IÎ R
S_{PASS_B}
R_th
"R"-Comp
COMP
32 μs
Debouncer
SWI_Cmp
PC20060926.3
Figure 12: Simplified Schematic Diagram of the SWI Comparator
As illustrated in Figure 14, a change in state is always synchronized with DriveHS or DriveLS. The same synchronization is valid for
updating the internal position register. This means that after every current pulse (or closing of S_TOP or S_BOT) the state of position switch
together with the corresponding position is memorized.
Using the GetActualPos commands reads back the ActPos register and the status of ESW. In this way the master node may get
synchronous information about the state of the switch together with the position of the motor. See Figure 13.
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