NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
L1 and matching network
optimized for specific PWB and
antenna layout. Recommend
0603 minimum size for L1 and
R2 and
recommended for
highest EMC resistance
R2
R3
other matching network inductors
for maximum efficiency.
BKGD/PTA4
RESET
AVDD
VDD
antenna
L1
RF
MATCHING
NETWORK
3.0 V
battery
0.1
F
0.1 F
VSS
AVSS
RVSS
VREG
LFA
LF
coil
R1
C1
FXTH87E
C4
LFB
XI
PTA0
XTAL
XO
PTA1
PTA2
PTA3
PTB0
PTB1
C2, C3, C4
optimized
for crystal
C5
470 nF
C2
C3
general
purpose I/O
aaa-027994
Figure 5.ꢀFXTH87E example application
The device labeled C4 in Figure 5, is drawn as a capacitor but may be any type of
passive component(s) sufficient to block or reduce unwanted external radiated signals
from corrupting the crystal oscillator circuit: PCB traces for the LFA/LFB, AVDD/VDD,
and VSS/AVSS pins and bypass capacitors should be minimized to reduce unwanted
external radiated signals from corrupting the power input circuits.
Care must be taken by the application to ensure the pressure applied to all surfaces of
the sensor remains equal. The sensor is constructed from nonhermetic materials and
should not be used as a seal between the tire pressure and the ambient environment
pressure.The seal should be provided by the final module design and not by the surfaces
of the sensor.
Note: A gel is used to provide media protection against corrosive elements which
may otherwise damage metal bond wires and/or IC surfaces. Highly pressurized gas
molecules may permeate through the gel and then occupy boundaries between material
surfaces within the sensor package. When decompression occurs, the gas molecules
may collect, form bubbles and possibly result in delamination of the gel from the material
it protects. If a bubble is located on the pressure transducer surface or on the bond wires,
the sensor measurement may shift from its calibrated transfer function. In some cases,
these temporary shifts could be outside the tolerances listed in the data sheet. In rare
cases, the bubble may bend the bond wires and result in a permanent shift.
4.4 Signal properties
The following sections describe the general function of each pin.
FXTH87ERM
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2019. All rights reserved.
Reference manual
Rev. 5.0 — 4 February 2019
8 / 183
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