L6208PD datasheet(13/27 Pages) STMICROELECTRONICS

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L6208

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

()

>1.5

µs (typ. value)

RCRISE

–







0.1

100

1 .10

Coff [nF]

Roff = 100kΩ

Roff = 47kΩ

Roff = 20kΩ

0.1

100

Coff [nF]

1.5

µs (typ. value)

L6208PD bảng dữ liệu(PDF) 13 Page - STMicroelectronics