L6228Q View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6228Q' PDF : 32 Pages View PDF
L6228Q
Circuit description
⎧tON > tON(MIN) = 2.5μs ⎫
⎨
⎩
tON
>
tRCRISE
–
tDT
⎬
⎭
(typ. value)
tRCRISE = 600 · COFF
Figure 15 shows the lower limit for the on time tON to get 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
working 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 the value for COFF, the more
influential the noises on the circuit performance.
Figure 14. 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]
Doc ID 14321 Rev 5
15/32
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