If the forward/reverse function of the NJW4303 is not used, is the dead time setting unnecessary? If not, what is the recommended processing method for the FRC pin?

If the forward/reverse function of the NJW4303 is not used and the FR pin is always set to a H level voltage, the dead time setting is not necessary.　The dead time can be minimized by setting the FRC pin open.
However, due to the effect of parasitic capacitance, even the dead time will not be 0 seconds.　In addition, since the FRC pin is high-impedance, it is possible that noise may cause malfunctions. Therefore, we recommend connecting a capacitor of 1 pF or more to the FRC pin.

The following is the formula for calculating dead time.

FR Dead Time Block – Dead Band Time

FR Dead band time is divided in two types depending on giving conditions.
The two dead band time are determined by the value of either FRC charged current or FRC discharge current IDCHGFRC, and the value of an external capacitor. To adjust the dead band time, change the value of CFRC. FR dead band time can be expressed as folowing: adjustment range for CFRC is more than 1pF. 

 

Symbol

Formula

Comments

FR Dead Band Time1

tDFRC1

tDFRC1 ≒ 140×103 ×CFRC

 FR: H → L (open)

FR Dead Band Time2

tDFRC2

tDFRC2 ≒ 100×103 ×CFRC

 FR: L (open) → H

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