NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
FXTH87ERM
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© NXP B.V. 2019. All rights reserved.
Reference manual
Rev. 5.0 — 4 February 2019
9 / 183
4.4.1 V
DD
and V
SS
pins
The digital circuits operate from a single power supply connected to the FXTH87E
through the V
DD
and V
SS
pins. V
DD
is the positive supply and V
SS
is the ground. The
conductors to the power supply should be connected to the V
DD
and V
SS
pins and locally
decoupled as shown in
Figure 6
.
Care should be taken to reduce measurement signal noise by separating the V
DD
, V
SS
,
AV
DD
, AV
SS
and RV
SS
pins using a "star" connection such that each metal trace does not
share any load currents with other external devices as shown in
Figure 6
.
4.4.2 AV
DD
and AV
SS
pins
The analog circuits operate from a single power supply connected to the FXTH87E
through the AV
DD
and AV
SS
pins. AV
DD
is the positive supply and AV
SS
is the ground.
The conductors to the power supply should be connected to the AV
DD
and AV
SS
pins and
locally decoupled as shown in
Figure 6
.
Care should be taken to reduce measurement signal noise by separating the V
DD
, V
SS
,
AV
DD
, AV
SS
and RV
SS
pins using a "star" connection such that each metal trace does not
share any load currents with other external devices as shown in
Figure 6
.
FXTH87E
V
DD
Bypass capacitors
closely coupled to
the package pins
FXTH87E and other load currents
star connected to battery terminals
The decoupling devices, although
drawn here as 0.1 F capacitors,
may be any type of passive component(s)
sufficient to block or reduce unwanted
external radiated signals from corrupting
the power input protection circuits;
application tuning may be required.
V
SS
AV
DD
AV
SS
RV
SS
IDD
ILOAD
to other loads
Battery
aaa-027995
0.1 F
0.1 F
Figure 6. Recommended power supply connections
4.4.3 V
REG
pin
The internal regulator for the analog circuits requires an external stabilization capacitor to
AV
SS
.
4.4.4 RV
SS
pin
Power in the RF output amplifier is returned to the supply through the RV
SS
pin. This
conductor should be connected to the power supply as shown in
Figure 6
using a "star"
connection such that each metal trace does not share any load currents with other supply
pins.
4.4.5 RF pin
The RF pin is the RF energy data supplied by the FXTH87E to an external antenna.
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