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CD4056B: CD4056BPW VDD & Vih, Vil voltage level

Mark Chen52
Expert 6555 points
Part Number: CD4056B
Other Parts Discussed in Thread: CD74HCT4511

Hi Expert,

Customer has question for VDD and A to D pin, If we use P3V3 for VDD and 1.8V voltage level into A~D pin, do we need level shift for 1.8V transfer to 3.3V?

Regards,

Mark

  • 0
    Guru 269490 points

    CD4000 devices are optimized for high voltages above 5 V; for voltages below 5 V, there are no guaranteed electrical characteristics. But even if we assume a VIH of 70% of VDD, this would be 2.3 V. You need a level shifter.

    There are no modern devices for this function because nowadays, this is typically implemented in software on the microcontroller.

  • 0
    TI__Expert 6701 points

    Hi Mark,

    I'm confused by the question a little are you referring to some type of setup like this?

    Also as clemens said the CD4000 family is typically used for higher operating ranges.

    We have a similar device in the CD74HCT4511 that operates better at these lower values.

    Regards,

    Owen

  • 0 in reply to Owen Westfall
    TI__Expert 6555 points

    Hi Owen,

    For customer’s request , they need the decoder support 0~F display, so they won’t use CD74HCT4511.

    But they are added level shift in schematic for BCD GPIO (1.8V to 3.3V), please help to check it in page9 as below file.

    vistara_1004_1100_Review.pdf

    There are some questions for CD4056BPW:

    1. There is no pin define in SPEC, what function for Pin1(STORBE), Pin6(DIS.FREQ.IN), PIN7(VEE)

    Regard,

    Mark

  • +1 in reply to Mark Chen52
    TI__Expert 6701 points

    Hi Mark,

    Pin 1 (Strobe) when high will push the inputs directly to the outputs, but when it goes low it will hold the previously applied output in the display.

    Pin 6 (DIS FEQ IN) when high the output led will be treated as active low however when low the outputs will be active high

    Pin 7 (VEE) Will be the low value of the output  If tied to ground when outputs are low they will be 0V

    Regards,

    Owen

  • 0 in reply to Owen Westfall
    TI__Expert 6555 points

    Hi Owen,

    How about the schematic ? do you have any concern on that?

    Regards,

    Mark

  • +1 in reply to Mark Chen52
    TI__Expert 6701 points

    Hi Mark,

    I have a worry that the outputs above 9 for the CD4056 are not A-F like in HEX for 10 it's L, for 11 it's H, for 12 it's P, for 13 it's -, and for 15 it's a blanking input. 

    For the schematic Pin 6 needs to be tied high, and unless you have some use for holding an input pin 1 should be tied high. pin 7 should be tied to ground, and everything else looks fine