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CD74AC164: Schematic example

Hardy Xue
Expert 3590 points
Part Number: CD74AC164
Other Parts Discussed in Thread: SN74HCS164

Hi Team,

Do we have CD74AC164 schematic and layout example can provide to customer for reference?

Best regards,

Hardy

  • 0
    TI__Mastermind 42600 points

    Hi Hardy,

    They can use references from other 164 devices like the SN74HCS164. That data sheet contains useful examples, I also recommend if possible that the customer use that device instead since its newer and will provide performance benefits.

  • 0 in reply to Dylan Hubbard
    TI__Expert 3590 points

    Hi Dylan,

    Thanks for your reply.

    There are 2 questions for SN74HCS164 as below:

    1. Why package show 16-pin? The actual pinout only 14 pins.

    2. What is the RC filter value is recommended?

    Best regards,

    Hardy

  • 0 in reply to Hardy Xue
    Guru 242930 points

    These packages do have 14 pins. The pin count below the image is an octal number wrong.

    The RC circuit must be slow enough so that the /CLR input is still low when VCC has reached the minimum supply voltage. So this depends on how fast VCC powers up.

  • +1 in reply to Hardy Xue
    TI__Guru* 96591 points

    Hi Hardy,

    Thanks for pointing out the error in the datasheet that the pin counts are wrong. You are correct that those should say "14-Pin" on both packages. I will put this in our errata list to fix in the next datasheet update.

    The values of R1 and C1 will depend on the customer's system requirements. What is their voltage supply ramp rate? Do they have a limitation on the startup time allowable for the shift register?

    To give you a reasonable estimate of the values required, I hope this inequality helps:

    dVcc/dt := power up ramp rate, in volts per second

    t_startup := maximum startup time allowable, in seconds

    This isn't precise, but it should give a reasonable estimate of the values required.

    -

    For example, if the power up ramp rate is 1us/V and the maximum startup time were 100us, then the range of values for tau would be:

    500ns < tau < 100us

    In this case, a 10k resistor and 1nF capacitor would work. Once a prototype system is built, these values could be adjusted to optimize operation.