• Resolved

SN74AVC4T245: can't set SN74AVC4T245PWR to sleep mode and get 5uA

Intellectual 450 points
Ilya Feldman

Replies: 10

Views: 107

Part Number: SN74AVC4T245

Hello TI support

Please help me to understand what is wrong in my schema/ connection.
I can't set SN74AVC4T245PWR to sleep mode and get 5uA

The left side of 1V8 come from, stand alone LDO the managed by LTE modem, once LTE modem ready to work it turn ON LDO 1V8.
The right side of 3V3 connected always. always under 3V3 power.

CS managed from CPU, on sleep mode Q2 is not connected and pin 15 and 14 tying to 3V3.

My device should work from buttery and power consummation is my issues.
When a SN74AVC4T245PWR is set as I wrote above i got total current consummation 1.2mA.
when i remove two units U5 and U4 from board the current reduced to 0.2mA

I set a pins of UARTs that going to controller as Analog inputs.
LTE modem U1 under shut down mode

What i am doing wrong? please advise.
I need insert two devices U5 and U4 to sleep mode
Thank you
Ilya

CATM.pdf

Intellectual 450 points
Ilya Feldman
  • Guru 107710 points
    Clemens Ladisch

    The I/O pins must not float. (The input buffers on the powered side are always active.)

    Ensure that all 3.3 V I/Os have (weak) pull-up or pull-down resistors.

    Or just use the SN74AXT4T245, which has integrated 100 kΩ ull-downs.

  • Intellectual 450 points
    Ilya Feldman

    In reply to Clemens Ladisch:

    Hi Clemens

    Tank you for suggestion, i will check ..... again

    Unfortunately i not found your alternative suggestion - SN74AXT4T245.

    maybe you made a mistake in Part Number ?

    Thank you

    Ilay

  • Expert 5340 points
    Chad Crosby

    In reply to Ilya Feldman:

    Hi Ilay,

    Clemens was referring to the SN74AXC4T245.

    Thanks!

    Chad Crosby

    Have a question about Logic or Level Translation?
    Find answers through our Logic Frequently Asked Questions

  • Intellectual 450 points
    Ilya Feldman

    In reply to Clemens Ladisch:

    Hi

    Yes, the 100 kΩ pull-downs solve the problem and device going to sleep and i got 4-5uA.

    Now :) i have a problem,UART side 1V8 going to CATM module. In order to insert my board to sleep mode I am shut down the CATM module. (because of that i can't configuration these pins to pull-downs)

    It causes UART in float mode and SN74AVC4T245PWR not insert to sleep mode.

    • Do you have Pin-to-Pin to SN74AVC4T245PWR that has integrated 100 kΩ pull-downs?
    • If i will add externally to SN74AVC4T245PWR, 100 kΩ pull-down i think it can mike a problem to UART Communication,yes?

    Thank you

    Ilya

  • Expert 5340 points
    Chad Crosby

    In reply to Ilya Feldman:

    Hi Ilya,

    The SN74AXC4T245PWR is Pin-to-pin compatible with the SN74AVC4T245PWR and has the integrated 100kOhm pull-downs.

    If you added 100kOhm pull-downs external to the SN74AVC4T245 - Those resistors should be too weak to impact UART performance.

    Thanks!

    Chad Crosby

    Have a question about Logic or Level Translation?
    Find answers through our Logic Frequently Asked Questions

  • Intellectual 450 points
    Ilya Feldman

    In reply to Chad Crosby:

    Hi Chad

    Thank you for a clear explanation and suggestion, i am ordered samples

    I want to learn from you :) , why there is a component SN74AVC4T245PWR without resistors ?

    I think SN74AXC4T245PWR is better, has integrated 100kOhm pull-downs. What are the pros and cons of these components

    Thank you

    Ilya

  • Expert 5340 points
    Chad Crosby

    In reply to Ilya Feldman:

    Hi Ilya,

    There's actually not too much different between these devices. The AXC is a newer version of the AVC device, and the AXC supports lower voltages than the AVC family.

    There's no real downside to switching to the AXC device, as both are equally as fast and have the same function.

    Thanks!

    Chad Crosby

    Have a question about Logic or Level Translation?
    Find answers through our Logic Frequently Asked Questions

  • Intellectual 450 points
    Ilya Feldman

    In reply to Chad Crosby:

    Hi

    Last question :)

    I not found in data sheet of AXC that it has integrated 100 kΩ pull-down

    can you show me a comment of that for my learning and undertending

    thank you

    Ilya

  • Expert 5340 points
    Chad Crosby

    In reply to Ilya Feldman:

    Hi Ilya,

    That feature is not listed on the datasheet, and is mostly internal knowledge.

    Thanks!

    Chad Crosby

    Have a question about Logic or Level Translation?
    Find answers through our Logic Frequently Asked Questions

  • Intellectual 450 points
    Ilya Feldman

    In reply to Chad Crosby:

    Thank you !! for all !!!


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