• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 21 subscribers
  • Views 813 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74LVC07A: Alternate For SN74LVC07

Matt Lang
Intellectual 560 points
Part Number: SN74LVC07A
Other Parts Discussed in Thread: TPL7407LA

I'm using the SN74LVC07APWRG4 parts. 

They are powered with 3.3V. The open drain is needed. But I noticed in the datasheet it says that the "Recommended Output Voltage" is 5.5V max. Since these are open collector, i'm not sure what this means. Does that mean the output MOSFET has a Breakdown voltage of around 6.5V due to the absolute maximum rating?

I need the output of these to handle being connected up to 12V when buffer is off. Can these parts handle 12V on the output directly with no resistor (when off of course)? This would be ideal.

Inputs:
I need them powered 3.3V because the MCU driving some of the inputs is only 3.3V and if powered by 5V, 3.3 does not meet the minimum high voltage threshold. But I also need the inputs to be 5V tolerant. preferable 12V tolerant? Do you have such a part?


Questions:
1) What does "output voltage" mean in this case of open drain outputs?
2) Do you have a component like these that can handle 12V inputs and outputs when powered by 3.3V? I'm looking for robust buffers for an open drain interface. Something around the same size and price.

3) Datasheet says "The input and output negative-voltage ratings may be exceeded if the input and output current ratings are observed." What about input and output positive-voltages? Does the 50mA clamp current apply to positive-voltages as well?

  • 0
    Guru 316940 points

    1. The output voltage is the voltage at the output pin. An open-drain output that is in the off state gets the voltage imposed by the pull-up resistor.

    2. The only logic devices that can handle voltages larger than 5.5 V are in the CD4000 family, but those do not have overvoltage-tolerant inputs. For higher voltages, use a power switch like the TPL7407LA.

    3. LVC family devices have ESD protection diodes between the I/O pins and ground; these diodes can pass up to 50 mA. There are no diodes to VCC (otherwise, the pins would not be overvoltage tolerant), so no current flows until you exceed the breakdown voltage and the device gets damaged.

  • 0 in reply to Clemens Ladisch
    Intellectual 560 points

    Thanks for the reply. I always get good part suggestion from this forum.

    1) So that means if I have the output with a 1k pull up resistor to 12V, it is being operated outside of the specification?

    2) The TPL7407LAPWR looks like a great part. I can power it with 12V and operate the inputs from 1.8 to over 12V. And the output voltage can be greater than 12V. That's perfect. The only thing is the price. Do you have one that is like this but cheaper? One with much lower continuous drain current ratings maybe?

    3) When you say "no current flows until you exceed the breakdown voltage" Is the 6.5V max output voltage the datasheet says the "breakdown voltage"? I don't see a direct breakdown voltage specification.

  • 0 in reply to Matt Lang
    Guru 316940 points

    1. Yes; 12 V is likely to break the output.

    2. The TPL7407LA is the cheapest of these switches from TI. How many channels do you need? Try the NUD3124(DM).

    3. The breakdown voltage is somewhere above 6.5 V.