BU21077MUV Datasheet, PDF (9/16 Pages) Rohm – Capacitive Switch Controller IC

BU21077MUV
Operational Notes – continued
11. Unused Input Terminals
Input terminals of an IC are often connected to the gate of a MOS transistor. The gate has extremely high impedance
and extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it. The small
charge acquired in this way is enough to produce a significant effect on the conduction through the transistor and
cause unexpected operation of the IC. So unless otherwise specified, unused input terminals should be connected to
the power supply or ground line.
12. Regarding the Input Pin of the IC
In the construction of this IC, P-N junctions are inevitably formed creating parasitic diodes or transistors. The
operation of these parasitic elements can result in mutual interference among circuits, operational faults, or physical
damage. Therefore, conditions which cause these parasitic elements to operate, such as applying a voltage to an
input pin lower than the ground voltage should be avoided. Furthermore, do not apply a voltage to the input terminals
when no power supply voltage is applied to the IC. Even if the power supply voltage is applied, make sure that the
input terminals have voltages within the values specified in the electrical characteristics of this IC.
13. Ceramic Capacitor
When using a ceramic capacitor, determine the dielectric constant considering the change of capacitance with
temperature and the decrease in nominal capacitance due to DC bias and others.
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TSZ02201-0L5L0F300820-1-2
14.Jul.2016 Rev.002