Datasheet

L6474 Phase current control
Doc ID 022529 Rev 3 27/52
7 Phase current control
The L6474 performs a peak current control technique described in detail in Section 7.1.
Furthermore, the L6474 automatically selects the best decay mode in order to follow the
current profile.
Current control algorithm parameters can be programmed by T_FAST, TON_MIN,
TOFF_MIN and CONFIG registers (see Section 9.1.5, Section 9.1.6, Section 9.1.7 and
Section 9.1.12 for details).
The current amplitude can be set through the TVAL register (see Section 9.1.4). The output
current amplitude can also be regulated by ADCIN voltage value (see Section 6.14).
Each bridge is driven by an independent control system that shares with the other bridge the
control parameters only.
7.1 Peak current control
The L6474 implements a peak current control algorithm with fixed OFF time. The control
cycle begins in the ON state: the opposite high-side DMOS low-side DMOS of the power
bridges are turned on according to the required current direction. In this way, the phase
current is increased according to the electrical model of the motor.
When the target current value is reached (this value is internally generated according to the
present value of the EL_POS register), the device switches to the OFF state in order to
make the phase current decay. During the OFF state both slow and fast decay can be
performed; the better decay combination is automatically selected by L6472 as described in
Section 7.2.
The t
OFF
value sets through the TOFF parameter of the CONFIG register and the value of
the TOFF_MIN register. If TOFF is greater than TOFF_MIN, it defines the OFF time of the
system. Otherwise the TOFF_MIN value is used.
Figure 9. Peak current control