LM393A: equivalent resistance

HARINI KRISHNA

Expert 1905 points

Part Number: LM393A

Hi,

I am using LM393A for a window comparator application.

I am using 3 ntc in parallel and one of them is given as input to the window comparator. I have 3 point voltage divider for the reference voltages of the window comparator.

could you please suggest if the ntc's temp_slb1,temp_slb2, temp_amb (from figure) should be placed in parallel or series?

Thankyou

Regards

Harini Krishna

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Harini,

I don't think that putting NTCs in parallel or in series is a good idea, if they are mounted at different locations and are sensing different temperatures.

I would spend each NTC its own window comparator.

Kai

0 HARINI KRISHNA over 4 years ago in reply to kai klaas69

Expert 1905 points

Hi kai

Thankyou for the suggestion.

As you said, all the NTC's are at different location sensing different temperatures.

The application uses window comparator only for one NTC measurement (temp_slb1 given in the figure.)

any suggestion on how do I rearrange the schematic for NTC?

Thank-you

Regards

Harini Krishna

0 Jonathan Nguyen over 4 years ago in reply to HARINI KRISHNA

TI__Expert 4555 points

Harini,

Where are the other two NTCs going to (temp_slb2, temp_amb)? Could you explain the function of each individual NTC?

Thanks,

Jonny

0 kai klaas69 over 4 years ago in reply to HARINI KRISHNA

Guru 140200 points

Hi Harini,

you could provide each NTC its own window comparator (U6) and connect all their outputs together, like a "wired or" (negative logic). Only one pull-up resistor would be needed then.

Kai

0 Chuck Sins over 4 years ago in reply to kai klaas69

TI__Mastermind 23425 points

Thanks Kai

That is a reasonable way to approach the application.

Chuck

0 HARINI KRISHNA over 4 years ago in reply to Chuck Sins

Expert 1905 points

Thankyou for the support.

This helped a lot

Regards

Harini Krishna

0 kai klaas69 over 4 years ago in reply to HARINI KRISHNA

Guru 140200 points

And does it work now?

Kai

0 HARINI KRISHNA over 4 years ago in reply to kai klaas69

Expert 1905 points

Hi Kai

We are yet to test it on the board

but we have a setup for the both the configurations now.

Thank you

Regards

Harini Krishna

0 kai klaas69 over 4 years ago in reply to HARINI KRISHNA

Guru 140200 points

Good luck!

Kai

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LM393A: equivalent resistance