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I have some queries and would be very thankful if can clarify the below mentioned questions from the datasheet of CD74HC4067

Link: http://www.ti.com/lit/ds/symlink/cd74hc4067.pdf

Link to previous relevant question: Maximum current on CD74HC4067

  1. Can you also provide an insight what the DC Vcc or Ground Current Icc = 50mA refers to. Is this current apart from the current per pin? I am using this in a battery powered application and current consumption is an important parameter in calculating the battery life.

  2. Is the total current consumed equal to 25+50 = 75mA at a time?

  3. Should I also include other currents like Input Diode Current, Drain Current and Output Diode Current?

Apologies for asking basic questions, I am new to battery powered electronic domain.

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    \$\begingroup\$ Absolute maximum ratings are extreme cases and not normal operating currents. \$\endgroup\$
    – Andy aka
    Apr 9, 2018 at 10:43
  • \$\begingroup\$ The 74HC4067 is a CMOS logic chip. It contains CMOS logic. A property of this kind of logic is that it has a very low static current (inputs fixed at one or zero), see datasheet top of page 4: Icc < 160 uA. In practice Icc will be a less than a few uA when the IC is static. Only when you toggle the IC's inputs will it consume more current. How much depends on the frequency with which you toggle the inputs. \$\endgroup\$ Apr 9, 2018 at 12:25
  • \$\begingroup\$ Thank you for the insights Andyaka and Bimpelrekkie. I my opinion while estimating the capacity of LiPo battery I consider absolute maximum ratings in case Typical ratings are not give. It gives the rough estimate what would be the increase in the size of your device due to battery. In my case the ic is always acquiring data so it is always ON. Thanks again. \$\endgroup\$
    – Abhinandan
    Apr 15, 2018 at 7:16
  • \$\begingroup\$ I would like to share some more details I found while searching for the above mentioned currents. Feel free to go through the datasheet. Link: ti.com/lit/an/scla008/scla008.pdf \$\endgroup\$
    – Abhinandan
    Apr 15, 2018 at 7:20

1 Answer 1

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Current per pin and Total/Ground/VDD currents are basically thermal maximum limits set by the internal track widths connecting to the pins. At some point above this, you fuse/overheat something.

Not surprising when you think about how little aluminium there must be in the tracks on a chip.

I was surprised in a chip design that the tracks had to be bigger than the fets themselves to carry the current (in that particular process). Simple chips only have a few metal layers, and while process changes make the fets smaller, they don't change the resistance of aluminium

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  • \$\begingroup\$ Thank you for the information Henry Crun. While is a surprising fact for me as well. Thanks for sharing the information. I would like to share some more details I found while searching for the above mentioned currents. Feel free to go through the datasheet. Link: ti.com/lit/an/scla008/scla008.pdf \$\endgroup\$
    – Abhinandan
    Apr 15, 2018 at 7:20

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