NXP Semiconductors UM11227 - Page 193

NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
193 / 205
NTM88
V
D
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Bypass capacitors
closely coupled to
the package pins
NTM88 and other
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The de
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A
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SS
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V
SS
IDD
ILOAD
to other loads
Battery
aaa-032034
C
2
C
3
Figure 61. Recommended power supply connections
reset
initiated
> 100 nsec
RST_B
GND
aaa-031047
0.3 V
DD
0.7 V
DD
Figure 62. RESET pin timing
Additional components or printed circuit artwork, not depicted in Figure 60, may be
necessary to sufficiently block or reduce unwanted external radiated signals from
corrupting the crystal oscillator circuit or power supplies. Minimize PCB traces for LFA /
LFB, AVDD / VDD, and VSS / AVSS pins and bypass capacitors to reduce unwanted,
external radiated signals from corrupting the power input circuits.
The application should assure the pressure applied to all sensor surfaces remains equal.
The sensor is constructed from non-hermetic materials and should not be used as a
seal between the tire pressure and ambient environment pressure. The seal should be
provided by the final module design, not by the surfaces of the sensor.
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 occupy boundaries between material
surfaces within the sensor package. When decompression occurs, gas molecules may
collect and form bubbles, or 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 be shifted from its calibrated transfer function. In some
cases, these temporary shifts could be outside the tolerances listed as part of this data
sheet. In rare cases, the bubble may bend the bond wires, and result in a permanent
shift. The media may also contain electro-static elements. If the highly pressurized media
permeates the gel, including contact with the wires or IC surfaces, the same type of
permanent shifts can occur, due to the electro-static elements disturbing the calibrated
transfer function.
The moving parts of micro-machined electro-mechanical systems (MEMS)
accelerometers are fabricated from materials that may adhere to each other when forced
into contact. Known as 'stiction', if this occurs, the sensor measurement may be shifted
from its calibrated transfer function. In some cases, these temporary shifts could be