SETTLING

PHASE

TRACKING UP

STEP UP PHASE

ISTEP_N

ISTEP_N+1

tOFF

tOFF

tON

Figure 2. Adaptive Decay Step Up

When a Step Down command is received, a mixed mode with 30% Fast is enforced for fast tracking. When during a Slow

Decay Interval the current is found lower than the new target, a tON phase in enforced causing the current to reach the

desired level.

During the Settling/Steady-State Phase, variable fixed slow decay ratios are used with the purpose of minimizing the

ripple. Initially, a slow decay is enforced for a fixed OFF time (tOFF). In the following cycles, the ON time interval (tON) is

monitored cycle by cycle. If tON is found equal to tON(MIN), then a mixed mode with 10% fast decay is applied to the next

chopping cycle.

● The fast decay percentage dynamically increases with +10% steps if tON in the previous cycle was found equal to

tON(MIN).

● The fast decay percentage dynamically decreases with -10% steps if tON in the previous cycle was found longer than

tON(MIN).

To facilitate the convergence of the algorithm, the fast decay percentage is not allowed to go back below 10%.

The Figure 3 graphically illustrates the behavior.

MAX22210

36V, 3.8A Stepper Motor Driver

with Integrated Current Sense

and 128 Microstep Indexer

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