Häufig gestellte Fragen (FAQ) |ROHM Semiconductor

FAQ Category

Simulation model

Product Replacement

Unused circuit / terminal, NC terminal processing

Operating power supply voltage (range / variation)

When power supply is not applied / OFF / 0 V

Input voltage (VIH / VIL)

Output current

Output (rise / fall / transmission) time

FAQ's

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Are there any important points to keep in mind when switching from the 74HC series of standard logic ICs to the 4000 series?
- The 4000 series of standard logic ICs features a max. supply voltage of 16V and 18V withstand voltage logic, so at low supply voltages operating speed will slow down and MOS transistor ON resistance increase compared with the 74HC series of low voltage logic ICs.

For standard logic ICs, although it states that it is appropriate to connect unused input terminals to the power supply or ground, is it necessary to connect a resistor in series?
- Although resistance is not strictly necessary for pull-up or pull-down, since the input pin has a high impedance, it may be affected by external noise when connecting a resistor on the order of MΩ.

For standard logic ICs, are there any concerns when VDD is open?
- Since the VDD pin is connected to the chip substrate (N type), it must be kept at the highest potential at all times. When voltage is supplied to other pins while VDD is open, parasitic element(s) may operate, possibly causing deterioration and/or destruction.

Is it possible to use standard logic ICs at a supply voltage of 2.7V?
- The minimum operating supply voltage of the 4000 series is 3V, so it cannot be used at 2.7V.

For standard logic ICs, what are the values of V_IH and V_IL when the supply voltage VDD is other than the values listed in the datasheet (5/10/15V)?
- The input threshold voltage for switching between 'H' and 'L' is approx. VDD/2 with respect to the supply voltage VDD. V_IL becomes 'L' when below 30% of VDD (V_IL＜VDD×0.3) and V_IH becomes 'H' when above 70% of VDD (V_IH＞VDD×0.7). For example, with VDD=3.3V, V_IH＞2.31V、V_IL＜0.99Ｖ.

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