14

ATA6830

4575C–BCD–05/03

Figure 13. Chopper Current Control

Figure 14. Current Flow in Halfbridge

Exception Handling

During operation, different exceptional states or errors can arise to which the circuit

must correspondingly react. These are described below:

•

Supply voltage below 9 V

Travel operation is suspended for the duration of the undervoltage. The output current

will be set to zero. When the supply voltage rises above 10.5 V, travel operation

restarts.

•

Supply voltage above 20 V

Travel operation is suspended for the duration of the undervoltage. The output current

will be set to zero. When the supply voltage falls below 20 V, travel operation restarts.

•Overtemperature warning

The maximum stepping speed is reduced to 300 Hz. This ensures a safe shut-off proce-

dure if the temperature increases to shut-off temperature.

•

Overtemperature shut-off

coil current

turn on signal

flyback

comparator

shunt resistor

voltage

blanking time

ON

OFF

ON

OFF

ON

OFF

OFF

ON

a)

b)