Data Sheet

TB67S279FTG, TB67S289FTG, TB67S249FTG Application Note
2018-03-07
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Preliminary
6.3. Constant current waveform when chopping frequency changes
Chopping frequency (fchop) is recommended to set about 67 kHz in using the IC. When the
chopping frequency is increased, ripple current of the motor is decreased and the waveform quality
is improved. However, the heat generates because the increased chopping frequency enhances the
switching loss. To improve the waveform quality, increase the chopping frequency. To reduce the
heat generation, decrease the frequency.
Example 1: When chopping frequency (fchop) = 100 kHz,
Figure 6.2 Chopping frequency (100 kHz)
Example 2: When chopping frequency (fchop) = 72 kHz,
Figure 6.3 Chopping frequency (72 kHz)
Generally, it is recommended to use the IC with the frequency range of 50 kHz to 120 kHz based
on 67 kHz as a typical value.
Slow
Fast
Charge
NF
Slow
Fast
Charge
NF
fchop = 72 kHz
fchop = 72 kHz
Step following capability is
slow.
The number of chopping is small (Switching loss and heat are small)
Set current value
Set current
value
Slow
Slow
Fast
Charge
Fast
Charge
NF
NF
Slow
Fast
Charge
Fast
Charge
NF
NF
fchop = 100 kHz
fchop = 100 kHz
fchop = 100 kHz
fchop = 100 kHz
Step following capability is fast.
The number of chopping is large (Switching loss and heat are large)
Set current value
Set current
value