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LMT70: LMT70

Henry Gu
Prodigy 10 points
Part Number: LMT70

Hi,

Datasheet: https://www.ti.com/lit/ds/symlink/lmt70.pdf?HQS=dis-dk-null-digikeymode-dsf-pf-null-wwe&ts=1685638558051&ref_url=https%253A%252F%252Fwww.ti.com%252Fgeneral%252Fdocs%252Fsuppproductinfo.tsp%253FdistId%253D10%2526gotoUrl%253Dhttps%253A%252F%252Fwww.ti.com%252Flit%252Fgpn%252Flmt70

This is the configuration we currently have:

We are consistently seeing 10mV noise on oscilloscope, which is greater than our allowable error, being that 5mV is 1degC.

These are the readings on the oscilloscope.

Should we change c2 to 0.1uF as per data sheet? Does capacitance matter that much?

We are taking a reading every 1s, using SAADC on nRF5340.

Are there any suggestions to reduce noise?

Best regards,

Henry

  • 0
    TI__Prodigy 480 points

    Hi Henry,

    I have a few comments/questions to help me understand your set up before I offer a suggestion:

    1. The C2 value is fine in this case however are you using 1 cap total or does each LMT70 have its own cap connected to VDD? If there is only 1 total, I would recommend having 1 for each LMT70.
    2. Does the oscilloscope reading you included show a reading when the ADC is active or not active? If this shows when the ADC is active, is the noise the same when the ADC is not active?
    3. Could you show us how the part is connected to the ADC?

    Best,

    Rooshi