NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
3.2 Multi-chip interface
The FXTH87E contains two to three devices using the best process technology for each.
• Microcontroller with accelerometer and pressure sensor interfaces, and RF transmitter
(MCU)
• Optional ranges on pressure transducers
• Optional XZ- or Z-axis acceleration transducer
As shown in Figure 1, the MCU interfaces to the RF transmitter using a standard memory
mapped registers. The transducers connect to the MCU using custom analog interfaces
and inter-chip bonding wires.
3.3 System clock distribution
The various clock sources and their distribution are shown in Figure 2. All clock sources
except the low frequency oscillator, LFO, can be turned off by software control in order to
conserve power.
MCU
SYSTEM
CONTROL
LOGIC
LFO
OSC
ACD10
CLOCK
RTICLKS
1 ms
PERIOD
RTI
ADC10
ADC10
PAR
REG
RAM
FLASH
BUSCLKS[1:0]
ADCCLK
HFO OSC
1, 2, 4,
and 8 MHz
f
f
OSC
BUS
4 kbps
LF
÷2
COPCLKS
CLSA, CLKSB
(125 kHz)
CPU
WATCH
DOG
LFRO
OSCILL
TPMI
LFR
BDC
PWU
FRC
CH0
CH1
f
(1 kHz)
LFO
RANDOM
(0 to 1 MHz)
PTA3
PTA2
TCLKDIV
f
(1 kHz)
LFO
DX (500 kHz)
÷8
RANDOM
(0 to 1 MHz)
LFOSEL
f
MFO
f
MFO
BIT
RATE
GEN
MFO
OSC
RF STATE
MACHINE
8
s
XTL
OSC
26 MHz
f
XCO
DATA
BUFFER
PLL
VCO
XI
XO
SENSOR MEASUREMENT
INTERFACE
RF
OUT
41.67 kHz
sampling
41.67 kHz
sampling
41.67 kHz
sampling
PRESSURE
SENSOR
X-AXIS
SENSOR
Z-AXIS
SENSOR
TRANSDUCERS
aaa-027990
Figure 2.ꢀClock distribution
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
5 / 183
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