CD4071B: Output current

Hi Asaf,

The output current described in the 'static electrical characteristics' table is associated with a particular output voltage.

I highlighted the case for 15V above.  You can see that the output voltage (V_O) is 1.5V for I_OL and 13.5V for I_OH.  So, to be clear, at the currents shown, the device will not have more than 1.5V output in the low state or less than 13.5V output in the high state at the given current values.

These are measured values, so they give you an idea of how the device should work.  For example, if you were to draw 6.8mA from the output in the high state, you would expect the voltage to sag from 15V down to 13.5V at 25C.

The question of "how much do I need to limit the current" is directly related to "what voltage do you need at the output?" -- if you want to get 15V, then you should draw very little current (less than 100uA).  If you are ok with getting 13.5V, then you can draw up to the listed value for the temperature range you are using.

For example, if you are operating at 15V and need to maintain 13.5V from -55C up to 125C, then you can't source or sink more than 2.4mA.

Hello  Emrys Maier,

Thanks for your reply.

The circuit I desgin has an output from the CD4071B to the outside world, so I need to protect it incase someone accidentally shorts the output.

I understand that the output voltage declines with the output current.

I want to make sure that when the output is shorted, the device wont be damaged.

The normal current drawn from this output is about 100uA, so in normal operation there is no problem.

When using 5V supply, can I limit the output current to 6.8mA in case of short circuit, or should I limit it to lesser current?

Thanks, and best regards,

Asaf Abraham