14

4575D–BCD–09/05

ATA6830

3.10

Bridge Current Control

The bridge current is controlled by a chopper current control, shown in Figure 3-11. The current

is turned on every 40 µs (25 kHz chopper frequency). The current flow in the H-bridge is shown

in Figure 3-12a. After a blanking time of 2.5 µs to suppress turn-on peaks the current is mea-

sured 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 3-12b.

Figure 3-11. Chopper Current Control

Figure 3-12. Current Flow in Halfbridge

coil current

turn on signal

flyback

comparator

shunt resistor

voltage

blanking time

ON

OFF

ON

OFF

ON

OFF

OFF

ON

a)

b)