I'm trying to determine whether a CD4013BE ("CMOS Dual D-Type Flip Flop") can take damange if one of the outputs (Q or Q-bar) is set to high, but shortened to ground (or vice versa) with no resistor in between. (I just take this particular IC as an example as it is something I'm currently working with, but I'm wondering how to determine this in general.)

Other ICs I have looked at have a specified maximal output current - which would let me determine what kind of resistor I can append to the output to protect the device in case of a short circuit. But even then many times it is not clear if this is just e.g. the safe output current without the voltage dropping, or whether exceeding this limit will actually damage the circuit.

The datasheet (pdf) only specifies a maximal input current of 10mA, but I think since it has a separate supply input this is not relevant for what I'm trying to determine.

So how can I determine whether and how I need to protect the output pins if I anticipate a possible short circuit?


1 Answer 1


datasheet says

Device dissipation per output transistor: 100 mW

There's your output current limit. if it's running from a 5V supply if you short it to ground and more than 20mA flows you've exceeded that. At 5V this seems unlikely to be possible, the outputs just can't produce that much current.

However at 15V Vcc it's only 6.7mA to damage it - and that's probably attainable with real-world parts.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.