L6256 datasheet(20/28 Pages) STMICROELECTRONICS

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output stage flyback diode voltage.

Off Time One Shot

The off time one shot guarantees that a minimum

off time occur in the output of the spindle PWM

waveforms. This prevents subharmonic cycling,

and prevents partial transition in the output wave-

form. Additionally, it provides a fixed time delay

which allows acurate synchronizing of the PWM

waveform with the commutation input (SP_CLK).

Finally, it prevents tolerance buildups in the cir-

cuitry because the PWM_DC circuitry can be de-

signed to allow higher than full scale voltage with-

out fear for causing audible subharmonics.

Output Comparator

This comparator produces the PWM chop duty

cycle for use within the spindle drivers, now cor-

rected for power supply variation.

On delay Comparator

The on delay comparator provides a warning sig-

nal for the back EMF detection circuit brackets

the worst part of the turnon transient that occurs

on the back emf detection winding.

Figure 10. Supply Feedforward Circuit Diagrams.

L6256

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L6256 Arkusz danych(PDF) 20 Page - STMicroelectronics