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CD40109B in high-to-low configuration input threshold level

Burkhard Kaas
Prodigy 40 points
Other Parts Discussed in Thread: CD40109B

Good Day,

We are using the CD40109B in high to low configuration:

VDD=3.3V
VCC=15V
All Enable (2,7,9,15) = 15V

Input threshold is 0.85V (H-L transition) / 1.15V (L-H transition):

This doesn't seem to comply with the datasheet. Can you please investigate?

Best Regards,

Burkhard

  • 0
    TI__Mastermind 46480 points

    Hi Burkard

    If you look in the datasheet at figure 9 and extrapolate the 15V Vcc line down to 3.3V you will see your reads for the switching  threshold are about  right.

    The problem with the CD4XXX parts is they are specd to operate from 3V to 18V but only tested at 5,10, and 15V.

    so basically they are only guarranteed to function at the voltages outside of 5V to 15V range. There are no specs at 3.3V. These part are speced this way for all of our competitor parts also. I dont know why they are not tested across the full range of Vcc and Vdd.