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CD54HC4351: Maximum current in addressable latches

Rahul S63
Prodigy 180 points
Part Number: CD54HC4351
Other Parts Discussed in Thread: CD74HC4351, TMUX1208

In active state, how much current can an addressable latch serve?

1. Per active pin

2. Maximum output across all pins together

Note that at any given moment, when the latch operates in the memory mode, there could be more than one active pin, due to a previous operation. In such a case, for the CD74HC4351 should we derive the max current per pin? The data sheet specifies trh maximum DC Switch Diode Current for a few VEE combinations but the question is on how to divide the current when we operate all 8 pins at the same moment.

How do I infer/calculate these quantities from the datasheet? Can anyone help with a few examples kindly?

Thanks in advance,

Rahul

  • 0
    TI__Genius 17085 points

    Hello Rahul,

    As shown in the datasheet, the performance parameters are tested and ensured at 1 mA output per channel.  

    Higher current may be possible but is not characterized.

    I will close this thread.  If you have more questions about it, just reopen it.  The expert on this product will be out of the office until next week.

  • 0 in reply to Kirby Kruckmeyer96848
    Prodigy 180 points

    Thank you for the prompt response.

    I am afraid designing based on just the 1mA characteristics may be quite unsafe.

    As I research more, I found some notes on the calculation of this current based on the Max power dissipation. The Load switch design documentation contains a few references to the ON Resistance and the voltage changes expected in the load, as a basis to calculate the power dissipation. I think that there is nothing in this document that may not apply to Analog multiplexers with a latch (like the CD4351). Can your expert team comment on this assumption? I am talking about this document:

    Thanks again..

    Rahul

  • 0 in reply to Rahul S63
    TI__Genius 17085 points

    Rahul,

    we have a holiday weekend.   The expert on this part will respond on Tuesday.

  • 0 in reply to Kirby Kruckmeyer96848
    TI__Guru 62930 points

    Rahul,

    This device is an analog multiplexor, and is not a load switch.  The document you referenced does not directly apply to this device.

    This device can enable only 1 of the 8 outputs at any given time.  This can be seen in the truth table on page 2.

    For the absolute maximum current for the single output:   The specification

    DC Switch Current, IOK (Note 3)
    For VI > VEE -0.5V or VI < VCC + 0.5V . . . . . . . . . . . . . . . . .±20mA  

    Applies.

    This is the situation where protection diode is not conducting as input is in normal operating range.

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade

  • 0 in reply to Wade Vonbergen
    Prodigy 180 points

    Dear Mr. Wade,

    Thank you for the clarification. I see what you are saying..

    On a parallel note, do we have any ICs like the TMUX1208/09 but with a latch? I want 8 analog signals to be remembered by the IC, until an instruction is passed to the chip.

    Regards

    Rahul

  • 0 in reply to Rahul S63
    TI__Guru 62930 points

    Rahul,

    I support the military logic devices.  I do not have significant insight into the analog muxes.  I suggest you post a query on E2E using the TMUX1208 as the device in question.  This will redirect the inquiry to the team with most knowledge on these devices.  They may be able to point to device that you desire.

    If this answers your question, please click "This Resolved My Issue"
    Regards,
    Wade