L6228 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6228' PDF : 34 Pages View PDF
L6228
tON > tON(MIN) = 2.5µ s (typ. value)
tON
>
tRCRISE
–
tDT
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
1 .104
Roff = 100kΩ
1 .103
Roff = 47kΩ
Roff = 20kΩ
100
10
1
0.1
1
10
100
Coff [nF]
Figure 13. Area where tON can vary maintaining the PWM regulation.
100
10
2.5µs (typ. value)
1
0.1
1
10
100
Coff [nF]
13/26
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