PWM current control
,287
95()
56(16(
Figure 10. Output current regulation waveforms
W2))
W21
W2))
96(16(
95()
6ORZGHFD\
6ORZGHFD\
L6235
95&
9
9
W5&5,6(
W5&)$//
W5&5,6(
W5&)$//
21
2)) 6<1&+5212865(&7,),&$7,21
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%
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Figure 11 shows the magnitude of the off time tOFF versus COFF and ROFF values. It can be
approximately calculated from the equations:
Equation 1
tRCFALL = 0.6 · ROFF · COFF
tOFF = tRCFALL + tDT = 0.6 · ROFF · COFF + tDT
where ROFF and COFF are the external component values and tDT is the internally generated
deadtime with:
Equation 2
Therefore:
20 K ROFF 100 K
0.47 nF COFF 100 nF
tDT = 1 µs (typical value)
Equation 3
tOFF(MIN) = 6.6 µs
tOFF(MAX) = 6 ms
14/35
DocID7618 Rev 2