LM339: Shutdown Behavior

Hi Anthony,

The Rev "C" SPICE model is a macromodel.

We do not specifically model shutdown behavior, but the model has a "feature" where the output is forced to 1/2 the supply voltage if either the input range or supply voltage is violated.

THE REAL DEVICE WILL NOT DO THIS - This strange behavior "feature" is to warn of violating the datasheet specifications.

In power-down, the model output will go to *half" the supply voltage when the supply drops below 2V *OR* either of the inputs are above 2V below the supply voltage (violate VCC-2V input range, which can easily happen when things are collapsing). So you may see some strange behavior.

Please see the LM339 family application note. It explains the input range limitations and section 6.10 shows the power-down behavior of a real device.

Application Design Guidelines for LM339, LM393, TL331 Family Comparators

What is your supply voltage? If you need controlled shutdown, see the TLV1824, which has a POR circuit that will provide a controlled power-down (output goes high-Z when supply drops below 2.4V - see section 7.4.3 of the datasheet). Also see the LM339LV if your supply voltage is below 5V.

There is an older transistor level model, but it is very simple and I cannot vouch for how accurate it would be under shutdown/undervoltage conditions.

LM139A PSpice Model

There are no model will perfectly model the shutdown behavior.