LP2989 error flag / current limiter?

All depends how much current the DSP pin can source when pulled low by the ERROR pin.

Datasheet suggests that the ERROR pin not sink more than 150uA, otherwise a low level on the ERROR pin may not be low enough.

Hello Donald,

Thank you for the reply.

I am not sure I am following up how these sentences join to a result.

DSP is TMS320f28335 (Experimenter Kit). 28335 and I believe most or all DSP's can provide up to 150uA in any IO pin. So if this is the max. current value that the LP2989 comparator sinks when low, I believe there is no reason to check on that - am I missing anything?

Now, what I found in the datasheet is the "Condition" Io(COMP) = 150uA for Output LOW Voltage. I am particularly not sure if this is the measurement condition (it seems to be) or a real limiter present in the chip circuit, ie, it will never sink/source any more than that. So, can you please tell me if a need a current limiting resistor interfacing and what is its recommended value.

The actual signal chain is LP2989 Error Pin -> ADG732 (MUX) -> ISO721 (+5V/+3.3V) -> 28335 (DSP).

Thank you,

Thiago

Hello Donald,

Any thoughts?

tks!

There is no active current limit, per se.

The resulting voltage is a function of the collector-emitter saturation for the NPN transitor that pulls the pin low.

You can sink more current, but the resulting voltage is higher.