• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 18 subscribers
  • Views 955 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.

cmos latch up

Bnovus
Intellectual 490 points

How much of a problem is latch-up on the new logis familiesHC/HCT/AC/ACT? In the past, if the input voltage exceeded the supply voltage you would get the part to self destruct. On data sheets you see a max input current. If you design with a series resistor such that you never exceed the max input current-regardless of voltage on the other end of the resistor, are you assured that you will not see latch-up?

  • 0
    TI__Mastermind 46480 points

     It will be different for different families. The families you mention all will have clamp diodes to Vcc therefor you cannot exceed the current limit of the diodes.You can limit the current and use the diodes to clamp the voltage but there will be a point where the voltage gets high enough to leak across pins. This point is different for every part and the value is not tested.

    A lot of the newer families will have overvoltage tolerant inputs. This means there will be no clamp diode to Vcc. Thes parts can handle voltages higher than Vcc to the specd value but cannot go over that value even if you limit the current.

     

  • 0 in reply to Chris Cockrill
    Intellectual 490 points

    sounds like, in addition to the series resistor,a schottky diode from the input pin to Vcc will be a sure bet to prevent any risk of latch-up

  • 0 in reply to Bnovus
    TI__Mastermind 46480 points

    you are correct.

    Best regards      Chris C