L6470HTR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6470HTR' PDF : 73 Pages View PDF
Phase current control
L6470
7.4
BEMF compensation
Using the speed information, a compensation curve is added to the amplitude of the voltage
waveform applied to the motor winding in order to compensate the BEMF variations during
acceleration and deceleration (see Figure 15).
The compensation curve is approximated by a stacked line with a starting slope (ST_SLP)
when speed is lower than a programmable threshold speed (INT_SPEED) and a fine slope
(FN_SLP_ACC and FN_SLP_DEC) when speed is greater than the threshold speed (see
Section 9.1.11 on page 45, 9.1.12 on page 45, 9.1.13 on page 45 and Section 9.1.14 on
page 45).
Figure 15. BEMF compensation curve
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To obtain different current values during acceleration and deceleration phases, two different
final slope values, and consequently two different compensation curves, can be
programmed.
The acceleration compensation curve is applied when the motor runs. No BEMF
compensation is applied when the motor is stopped.
7.5
Motor supply voltage compensation
The sinewave amplitude generated by the PWM modulators is directly proportional to the
motor supply voltage (VS). When the motor supply voltage is different from its nominal
value, the motor phases are driven with an incorrect voltage. The L6470 device can
compensate motor supply voltage variations in order to avoid this effect.
The motor supply voltage should be connected to the integrated ADC input through
a resistor divider in order to obtain VREG/2 voltage at the ADCIN pin when VS is at its
nominal value (see Figure 16).
The ADC input is sampled at fS frequency, which is equal to PWM frequency.
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