POWERSTEP01 datasheet(47/92 Pages) STMICROELECTRONICS

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powerSTEP01

Phase current control: current mode

Figure 23. Fast decay tuning during the falling steps

9.4

Torque regulation (setting the output current)

The phase currents are monitored through two shunt resistors (one for each power bridge)

connected to the respective sense pin (see Figure 24). The integrated comparator

compares the sense resistor voltage with the internal reference generated using the peak

value, which is proportional to the output current amplitude, and the microstepping code.

The comparison result is provided to the logic in order to implement the current control

algorithm as described in previous sections.

The peak reference voltage can be regulated in two ways: writing TVAL_ACC, TVAL_DEC,

TVAL_RUN and TVAL_HOLD registers or varying the ADCIN voltage value.

The EN_TQREG bit (CONFIG register) sets the torque regulation method. If this bit is high,

ADC_OUT prevalue is used to regulate output current amplitude (see Table 24 on page 60).

Otherwise the internal analog-to-digital converter is at the user’s disposal and the output

current amplitude is managed by TVAL_HOLD, TVAL_RUN, TVAL_ACC and TVAL_DEC

registers (see Table 18 on page 58).

The voltage applied to the ADCIN pin is sampled at fS frequency and converted in an NADC

bit digital signal. The analog-to-digital conversion result is available in the ADC_OUT

Falling step

1st fast decay:

tFALL = FALL_STEP/4

Falling step

1st fast decay:

FALL= FALL_STEP/2

2 nd fast decay:

FALL= FALL_STEP/2

Time

reference current

AM15052v1

POWERSTEP01 Datasheet(PDF) 47 Page - STMicroelectronics