Rainbow Electronics ATA6830 - Manual (Page 13)

13
ATA6830
4575B–BCD–01/03
If the chip temperature exceeds the overtemperature warning threshold, the step speed
is reduced to 300 Hz. If the chip temperature rises further the output driver is shut off.
Step Operation The stepping motor is operated in halfstep-compensation mode. The current for both
coils is shown in Figure 12. The current levels are increased when the temperature is
below 0
° C to secure operation. For final tests at the end of the application production
line the currents are reduced.
Figure 12. Compensated Halfstep Operation
Chopper Current Control The chopper current control is shown in Figure 13. The current is turned on every 40 µs
(25 kHz chopper frequency). The current flow in the H-bridge is shown in Figure 14a.
After a blanking time of 2.5 µs to suppress turn-on peaks the current is measured via the
shunt voltage. As soon as the current has reached its nominal value it is turned off
again. The current flow in this state is shown in Figure 14b.
Table 4. Maximum Step Frequency
V
BAT
Maximum Step Frequency
at Rising Voltage Maximum Step Frequency
(V
BAT
once > 10.5 V)
< 9 V No operation No operation
9 V to 9.5 V No operation 300 Hz (3.33 ms)
9.5 V to 10 V No operation 500 Hz (2.03 ms)
10 V to 10.5 V No operation 680 Hz (1,47 ms)
10.5 V to 11 V 850 Hz (1.17 ms) 850 Hz (1.17 ms)
> 11 V 1000 Hz (1 ms) 1000 Hz (1 ms)
> 20 V No operation No operation
700mA
500mA
-500mA
-700mA
700mA
500mA
-500mA
-700mA
1 2 3 4 5 6 7 8
coil A
coil B
half steps
half steps