LMT86-Q1: Location of the RC filter

John Pan

Part Number: LMT86-Q1
Other Parts Discussed in Thread: LMT86

Hi Jalen,

Could you please advise the optimal location for the RC filter on PCB layout if the LMT86 temperature sensor is placed far from a microcontroller? Should be the output RC filter close to LMT86 or close to the MCU?

Thanks,

John

over 4 years ago

0 Jalen Tate89 over 4 years ago

TI__Genius 9675 points

John,

Please place the RC filter closest to MCU input for optimal performance.

Jalen

0 John Pan over 4 years ago in reply to Jalen Tate89

Intellectual 990 points

Hi Jalen,

Thank you very much for your quick reply. Could you please provide some justifications?

I thought that placing RC filter close to the LMT86 is a good way to keep the noise from entering the system (MCU), which is commonly used for input connector application. However, placing a capacitor (or a bypass capacitor) close to the pin of MCU is another common practice to reduce the noise.

Thanks again,

John

0 Jalen Tate89 over 4 years ago in reply to John Pan

TI__Genius 9675 points

John,

You are correct about the filtering, but you must keep in mind that the filter Cap is also being used to charge the sample cap of the ADC. It serves a dual purpose. If you have the RC filter on the LMT86 side you could see a voltage drop across the long trace to the MCU. You want the RC filter close to the MCU pin for this reason.

Jalen

0 John Pan over 4 years ago in reply to Jalen Tate89

Intellectual 990 points

Hi Jalen,

Thank you very much for your help. I understand the reason now.

Best regards,

John

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LMT86-Q1: Location of the RC filter