FXTH87E
NXP
but not necessarily for devices of the FXTH87E family. As a consequence, this function is not recommended for FXTH87E devices.
Application NoteNxp
TPMS Clocks Calibration for FXTH and NTM88 Devices
Instructions for calibrating internal oscillators in NXP FXTH and NTM88 TPMS devices to compensate for temperature-induced drift and maintain accurate timing and power efficiency.
Overview
This application note provides technical guidance on compensating for oscillator drift in NXP's Tire Pressure Monitoring System (TPMS) devices, specifically the FXTH87, FXTH87E, and NTM88 families. These devices utilize internal Low Frequency (LFO), Medium Frequency (MFO), and High Frequency (HFO) oscillators that exhibit frequency deviation across temperature ranges. The document details how to calibrate the Periodic Wake-Up (PWU) block by adjusting the WDIV register based on the actual LFO frequency. It describes calibration methods using either a 26 MHz external crystal or the bus clock as a reference to calculate precise timing. The note also outlines firmware library functions (TPMS_LFOCAL) and provides implementation strategies to ensure consistent wake-up intervals, which is critical for minimizing power consumption and extending battery life in automotive sensor applications.
Use Cases
- Compensating for temperature-induced timing errors in tire pressure sensors.
- Optimizing battery life by ensuring accurate periodic wake-up cycles.
- Implementing firmware-based oscillator calibration using external crystal references.
- Calibrating internal bus clocks for precise communication timing in automotive environments.
Topics
FXTH87
FXTH87E
NTM88
TPMS
oscillator drift
LFO
MFO
HFO
clock calibration
temperature compensation
Periodic Wake-Up
WDIV register
Referenced Parts
FXTH87
NXP
This function uses the 26 MHz external crystal to calculate the LFO frequency. It returns valid results when the LFO frequency range remains between 660 Hz and 1900 Hz, which is the case for FXTH87 devices
NTM88
NXP
The FXTH and NTM88 devices include three internal oscillators: the Low Frequency Oscillator (LFO) which has a target frequency of 1 kHz
FXTH
NXP
FXTH and NTM88 devices include three internal oscillators, a low frequency, medium frequency, and high frequency oscillator.
| FXTH87E | NXP | but not necessarily for devices of the FXTH87E family. As a consequence, this function is not recommended for FXTH87E devices. |
| FXTH87 | NXP | This function uses the 26 MHz external crystal to calculate the LFO frequency. It returns valid results when the LFO frequency range remains between 660 Hz and 1900 Hz, which is the case for FXTH87 devices |
| NTM88 | NXP | The FXTH and NTM88 devices include three internal oscillators: the Low Frequency Oscillator (LFO) which has a target frequency of 1 kHz |
| FXTH | NXP | FXTH and NTM88 devices include three internal oscillators, a low frequency, medium frequency, and high frequency oscillator. |