L6228Q datasheet(15/32 Pages) STMICROELECTRONICS

Part #	L6228Q

Description	DMOS driver for bipolar stepper motor

PDF	32 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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15 / 32 page

L6228Q

Circuit description

Doc ID 14321 Rev 4

15/32

tRCRISE = 600 · COFF

Figure 15 shows the lower limit for the on time tON for having a good PWM current regulation

capacity. It has to be said that t

ON is always bigger than t

ON(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 14.

tOFF versus COFF and ROFF

tON tON MIN

()

2.5

μs

RCRISE

–

⎩⎭

⎨⎬

⎧⎫

(typ. value)

0.1

100

1.10

Coff [nF]

Roff = 100kΩ

Roff = 47kΩ

Roff = 20kΩ

L6228Q Datasheet(PDF) 15 Page - STMicroelectronics