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CD4504B with VDD = 3V3

Kilian Noetzold
Intellectual 510 points
Other Parts Discussed in Thread: CD4504B, CD4050B, SN74HC244

Hello

I facing a Problem with a CD4504B. We are using this part to shift from 15V to 3V3. I have noticed that there was a PCN (Link) in 2004 on Page 4 changing the min Supply-Voltage from 3V to 5V.
Is it seam to work in our application with 3V3 but I like to know the reason for this PCN to find out if we have a problem.

Our Conditions:
VCC = 15V
VDD = 3V3
Select = VSS

Thanks
Kilian

  • 0
    TI__Mastermind 46480 points

    it does not work well at 3V as it was specd and barely worked at 3.3V. It may not alway work at 3.3V across temp and process. We tried but could not get it to work well in the 3V range so we moved the operating voltage to 5V where it does work.

  • 0 in reply to Chris Cockrill
    Intellectual 510 points

    Chris Thank you fast reply,

    Do you have more information’s about the barley operation at 3V3?

    Does the CD4050B work with 3V3?

  • 0 in reply to Kilian Noetzold
    TI__Mastermind 46480 points

    I dont have any more info. The CD4050 would not be any better.  I know they woked hard on this trying to get it to operate better at low voltage but were unsucess ful and changed the datasheet to 5V.

  • 0 in reply to Chris Cockrill
    Intellectual 510 points

    Do you have any recommendation for a level shift from 15V to 3V3?

    The input is signal is an open collector input with a 3K9 pull up to 15V, the signal is not fast but noisy. So I like to have a RC Low pass at the input.

    My best Idea is a simple voltage divider to shift from 5 to 3V3.

    Do you recommend a CD4050B or a CD4504B?

  • 0 in reply to Kilian Noetzold
    TI__Mastermind 46480 points

    unfortunately we do not have a single part solution for this right now.

    We do have one planned and would like to know how many you would use if we had one. Jus t want to know for business case.

    A fairly simple option would be to use a 3.3V buffer that has internal clamp diodes on the input. Something like the HC125 with a current limiting resistor on the input. This would allow the internal diode to drop the voltage down to Vcc +1VBe

    any of the SN74HC parts would work.

  • 0 in reply to Chris Cockrill
    Intellectual 510 points

    Thanks I think we will go for this

  • 0 in reply to Chris Cockrill
    Intellectual 720 points

    Chris Cockrill,

    It has been about 3 years since this response was posted. I am also on the search for a device that can convert (level shift) 15V to 3.3V. My application is interfacing with 12V (15V Max) mechanical switches that I need to sense with a 3.3V uController. This is done in an automotive environment. I am currently using a voltage divider preceding an op amp buffer to accomplish this, but I am getting tired of using 3 components to accomplish this task as I have many inputs to manage. compressing this 3 component design into a 1 component design would save me greatly on board space!!

    Is there any hope for me? Does TI offer such a device?

    Thank you!

    Marshall

  • 0 in reply to Marshall Folkman
    TI__Guru* 97046 points
    Hi Marshall,
    Unfortunately for all of us, the great Chris Cockrill has retired from TI - we all miss him and his many years of experience!

    To put my suggestion up front - have you considered using an SN74HC244 (or similar HC family buffer) with series resistors on the inputs? As long as the current into the input clamp diodes is limited (preferably below 1mA) then the SN74HC244 won't "see" a voltage on the inputs higher than Vcc + ~0.7V and it will output at 3.3V (or whatever supply you put on it from 2V to 6V). This would reduce your part count significantly, even though it isn't a perfect solution.

    Some care would have to be taken with the connected 3.3V rail design - most 3.3V supplies don't like sinking current so a shunt might have to be added - but still, a shunt regulator + 1 SN74HC244 and 8 resistors for 8 channels beats the other option IMO.

    ***

    As for an automotive high-to-low translator, we don't currently have anything specifically made for this, and it's unlikely to show up in the near future (within the next year or two). We have looked at 18V+ logic technology, and it remains on our creative backlog, but the demand is unfortunately relatively low and other projects continually get higher priority.

    I'm glad to get this feedback as it indicates continued interest in this line of parts. Can you expand on exactly what you would like to see? In automotive, I often see requirements for 40V max parts due to voltage spikes. Are there ESD requirements? Bit rates? How many channels would you want?