timer never times out if Trigger stays high.

Hi,

sorry for getting back to you so late.

You need to toggle TRIG low to high in order for the LTC6993-2 to generate a pulse.

Did you toggle TRIG?

This is the spec of TRIG from page 5 of the data sheet:

Petre

Petre:

Thank you for your reply

Yes I understand that I need to toggle this pin for it to work

The device is configured to POL = 0, so the one shot output pulses are high

Only one board is behaving this way.

This is happening at power up.

The situation is at power up the TRIG pin stays high and the output pin also stays high

My understanding is that the output pin should go low after it times out.

But it never goes down.

if the TRIG pin stays high then the output will stay high <== this is my question

Thank you

Fausto

HI,

"if the TRIG pin stays high then the output will stay high <== this is my question"

No. In the data sheet, at page 14 it is stated that a rising edge on TRIG initiates the output pulse and the output pulse is determined by NDIV and RSET, not by the fact the TRIG signal stays high or low. So even if the TRIG stays high, the pulse should go low after approximately 30s (if I calculated well based on your schematic)

There is also a possibility of multiple TRIG pulses that can keep the output high indefinitely. See how the TRIG behaves.

Usually, in such cases in which only one board does not function as expected and the others do, I recommend replacing the LTC6933 with a chip from a board that is functional. If the problem is solved, the previous chip was bad and if you want, you may contact your ADI representative to initiate a failure analysis. If the problem is not solved, you have a problem on the board and you'll have to debug it.

Petre