13

ATA6830

4575C–BCD–05/03

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

Bridge Current Control

The bridge current is controlled by a chopper current control, 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

Maximum Step Frequency

at Rising Voltage

Maximum Step Frequency

< 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

12345

6

7

8

coil A

coil B

half steps

half steps