L6228D datasheet(13/26 Pages) STMICROELECTRONICS

Numer części	L6228D

Szczegółowy opis	DMOS DRIVER FOR BIPOLAR STEPPER MOTOR

PDF	26 Pages

Scroll/Zoom	100%

Producent	STMICROELECTRONICS [STMicroelectronics]

Strona internetowa	http://www.st.com

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13 / 26 page

13/26

L6228

tRCRISE = 600 · COFF

Figure 13 shows the lower limit for the on time tON for having a good PWM current regulation capacity. It has to

be said that tON is always bigger than tON(MIN) because the device imposes this condition, but it can be smaller

than tRCRISE - tDT. In this last case the device continues to work but the off time tOFF is not more constant.

So, small COFF value gives more flexibility for the applications (allows smaller on time and, therefore, higher

switching frequency), but, the smaller is the value for COFF, the more influential will be the noises on the circuit

performance.

Figure 12. tOFF versus COFF and ROFF

Figure 13. Area where tON can vary maintaining the PWM regulation.

ON MIN

()

>2.5

µs (typ. value)

RCRISE

–







0.1

100

1 .10

Coff [nF]

Roff = 100kΩ

Roff = 47kΩ

Roff = 20kΩ

0.1

100

Coff [nF]

2.5

µs (typ. value)

L6228D Arkusz danych(PDF) 13 Page - STMicroelectronics