TMP275 Alert Pin as General Purpose Output

Richard DalleMolle

Other Parts Discussed in Thread: TMP275

I have an application in which I am not using the Alert function/pin of the TMP275. I'm wondering if it is possible to use it as a general purpose output in the following way.

I would set the T(high) limit register to its max value; set the T(low) limit register to its min value. Alert should never be asserted. Set Thermostat Mode (TM) to '0' for comparator mode.

I would like to use the temp sensor by setting Shut Down (SD) mode = 1, and only initiating conversions on demand by writing a '1' to the One Shot (OS) bit of the configuration register.

Under these circumstances, would writing values to the Polarity bit (POL) of the config register cause the Alert pin to change state (when POL=0, Alert=1, and POL=1, Alert=0, since Alert is not asserted)?

Does Shut Down mode shut down the POL function?

Thanks, Rich

over 13 years ago

0 Chris Featherstone over 13 years ago

TI__Mastermind 25060 points

Richard,

I suspect that this will work fine. I am currently looking into this and will get back to you soon.

0 Chris Featherstone over 13 years ago

TI__Mastermind 25060 points

Rich,

I have built up a test circuit with the TMP275 and programmed it in the following way:

I also set the T(high) and T(low) registers to their maximum and minimum values respectively.

I was successfully able to have Alert = 1 when POL = 0 and Alert = 0 when POL = 1.

The Shut Down mode does not shut down the POL function.

0 Richard DalleMolle over 13 years ago in reply to Chris Featherstone

Prodigy 20 points

Chris,

Thanks so much for taking the time to check this out in detail. It looks like this approach will work, which is excellent! Gives me that 1 bit of output that will keep me from adding a lot of unnecessary HW.

Rich

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TMP275 Alert Pin as General Purpose Output