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125KHz TX antenna adjust

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125KHz TX antenna adjust

‎06-25-2019 07:26 PM
1,498 Views
tedwu1
Contributor III

I have a development board of FRDM-KW019032. I use it to program a TPMS sensor that its MCU is FXTH87xx11. But the yield rate of programming seems no good. I use 125KHz to send the programming data to TPMS sensor. I want to know how to adjust the 125KHz TX antenna to make a good programming yield rate. Can anyone guide me?

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‎06-27-2019 02:00 AM
1,351 Views
TomasVaverka
NXP TechSupport
NXP TechSupport

Hi Ted,

Improving LF reception can be done by:

  • Hardware: please refer to the AN4391. For the LF antenna, we recommend a value of 7.2mH minimum; higher values will provide a better sensitivity, but take more space on the PCB. The value of 7.2mH can be a good trade-off.
  • Software: we do not recommend customers to modify registers LFCTRLB to LFCTRLE: these registers are configured in the reset vector with NXP recommended values. Sensitivity in LFCTL1 register should be selected carefully: it depends on the strength of the LF signal (high sensitivity is for weaker signals, and low sensitivity is for stronger signals). The DEQEN  function should be activated only if the LF signal is very strong and the LF coil saturates at low sensitivity.
  • Positioning the LF antenna of the programming tool parallel to the LF coil on the TPMS board. If the LF antenna and the LF coil are not parallel, reception will not be optimal.

I hope it helps!

Best regards,

Tomas

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