Data Sheet

TB67S279FTG, TB67S289FTG, TB67S249FTG Application Note
2018-03-07
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Preliminary
6.2.1. Function of internal oscillation circuit: Elimination of external components
The internal oscillation circuit of TB67S279FTG, TB67S289FTG, and TB67S249FTG has the
function of eliminating external components.
As mentioned previously, the oscillation frequency can be changed arbitrarily by connecting
external components (resistor and capacitor) to the OSCM pin and adjusting their constant
numbers. Also, the motor can be controlled by internal fixed frequency without using external
components.
When using this function, remove both resistor and capacitor and connect the OSCM pin to the
GND. When the IC recognizes that the OSCM pin is short-circuited, the internal oscillation circuit
switches to use the external-component eliminating mode.
In this mode, configuration of the internal oscillation frequency (f
OSCM
) is about 930 kHz and of
the constant current PWM (chopping) frequency (fchop) is about 60 kHz that is 1/16 of f
OSCM
.
6.2.2. Notes in using the component-elimination drive function of the OSCM pin
This function is activated when judging period of 20 μs (typ.) has passed after both POR and
STANDBY are released.
If the signal is input during this judging period, it may not be reflected correctly.
Therefore, do not input control signals during this period.
Moreover, while the motor is operating, be sure to fix OSCM mode to either the normal drive mode
or the external-component elimination mode. Switching the OSCM mode during motor operation is
prohibited.