Tire Pressure motivated by Auto mega trends

Mobility for everyone Cleaner world for everyone

• TPMS is available for all type of • TPMS allows optimum tire
vehicles including truck and inflation and thus fuel
busses consumption and CO2 emission
• Scalable solutions reduction
• Multiple pressure ranges • Maximizes tire life
• Multiple rotation axis • European and Korean legislation
• Multiple RF frequencies driven by CO2 reduction

Safety for everyone Always Connected

• Prevent roadside breakdown and • Provides accurate tire data to the
risk of road congestion driver
• US tread act to prevent roll over • Filling assistant app on smart
accidents phones
• Future possibilities to link tire • Fleets & Truck: enables better tire
information with chassis and management
ADAS system

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 TPMS legislation around the world
Region Requirements

USA Regulation from 2005: FMVSS138 mandates TPMS for new vehicles starting
from October 1st 2005

European Union Regulation from 2012: EC661-2009 mandates TPMS starting Nov 2012 for
new type approved vehicles and for all new vehicles starting from Nov 2014:
TPMS will be tested as part of the new EU standardized plan for vehicle
periodical inspection

S. Korea / Japan Regulation from 2013: TPMS vehicles to be installed on passenger cars from
January 2013 for new model and January 2015 for existing model

Russia, Kazakhstan, Valid from 2015 onwards & replaces nation legislation
Belarus (Eurasia)

Indonesia, Israel, Require European whole vehicle type approval for vehicles imported from
Malaysia, Philippines, Europe. As a consequence TPMS will be required for all new vehicles in
Turkey November 2014

China Recommended specification

Enforcement Standard in Preparation

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 MPXY8700 Packaging

Gcell
Pcell

MCU + RF

QFN 9 x 9 mm
Cavity Package
(Cross Section)

Gel
Selective encapsualtion

Metal cap

Plastic Plastic
housing Gcell housing
Gel Pcell

Plastic flag
Leadframe
Not to scale. For illustration purposes only.

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Tire Performance Issues
Worsening until around 1.5 ba, then improvement due to bell formation of tread
Aquaplaning (water depth >2 mm)
centre inwards (at rated load)
General durability Reduced with lower pressures

A reduction by 0.5 bar results in a worsening of 15 km/h in endurance (e.g.

Test Stand durability
Failure at 185 km/h instead of 200 km/h)
A reduction by 0.5 bar results in damage sustained at 20% lower speed (e.g. at
Resistance to curb impact
40 km/h instead of 50 km/h)
The limit value for unseating of bead from rim lies between the operating
Bead unseating from rim
pressure and 1 to 1.2 bar. For safety reasons, this should never be lower
Wear A tire with 20% lower pressure has a running life around 30% less

Rolling Resistance A reduction by 0.5 bar results in an increase in rolling resistance of around 15%
A deviation of 1 bar from normal pressure (2 to 2.5 bar) worsens the noise level
Tread Noise
by 2 dbA (66%).
On a mid-class car, an air pressure deviation of 0.2 bar from one axle is
Handling on dry and wet surfaces
noticeable.

(Source: Michelin Tires)

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Tire Performance Issues

100

80 108 140

Rolling Resistance (%)

Service Life (%)

60 106 130

Fuel Use (%)

40 104 120

20 102 110

0 101 100
120 110 100 90 80 70 60 50 40 30 2.0 1.7 1.4 1.1
Tire Pressure (% of Specified) Tire Pressure (bars)

Decreased Tire Life with Increased Fuel Use and

Lower Pressure Rolling Resistance with
Lower Pressure
(Source: Continental Tires)

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 Pressure Accuracy
• Measurement accuracy target varies with OEM
− Typical accuracies better than 8-10 kPa (1.2 – 1.4 psi)
− Typical resolutions of 1 to 2 kPa (0.15 – 0.30 psi)

• Accuracy over temperature, supply voltage and life of the

tire/system

• Must warn based on the correct Cold Inflation Pressure (CIP)

specified for the vehicle

• CIP limits usually set in the chassis receiver for a specific

vehicle

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 Pressure Accuracy
• Effects of absolute vs. gauge pressure at altitude
− In tire sensors measure absolute pressure
− Typical tire gages measure differential (gauge) pressure
relative to the atmosphere
• CIP is defined as the pressure of the tires after
the has been stopped for at least 1 hour
• The “corrected” pressure using the Ideal Gas Law
is not used
− It is not the mass of air present setting tire performance
− It is pressure of the air that defines the load carrying capability and
performance of the tire
• Generally accepted to use absolute pressure with a fixed
atmospheric offset (approx 100 kPa = 14.5 psi)

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TPMS System Solutions
• Direct (Measure Pressure in the Tire)
− Useabsolute pressure sensor inside the tire volume
− Communication via LF and/or RF links
− Mounted inside the tire/wheel

On the wheel (valve stem or drop center)

On the tire (side wall, bead area or tread belt)
− Powered by energy source

Internal
battery

Source other than battery (battery-less)

• Indirect (Measuring Some Other Parameter)

− Infer under-inflation by using parameter other than pressure sensing

Wheel speed variations

Ride height variations

Tire vibration variations
− No power source required on the wheel/tire

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Tire Pressure Monitor Systems: Indirect Measuring

• Implemented through ABS wheel

speed sensors
• ABS system is able to measure
individual wheel speed and
compare it against other wheels
• If a wheel is moving faster, it is
very likely it is under-inflated

http://www.aa1car.com/library/diagnosing_abs_wheels_speed_sensors.htm

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Tire Pressure Monitor Systems: Direct vs. Indirect
Direct Indirect

Precision ☺ 
Reaction time ☺ 
Detection of multiple ☺ 
faults
Position-dependant ☺ 
pressure warning
Robustness under ☺ 
different driving
conditions
Number of additional  ☺
components
System cost  ☺
Required driver ☺ 
interaction
Additional comfort ☺ 
features

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Tire Pressure Monitor Systems: Indirect Measuring

Like

• Hardware reuse (ABS system)

• Cheap

Don’t like

• Measurement relative to other tires

• Can only sense
• One under-inflated tire
• Three tires are under-inflated
• Two diagonally-positioned tires are under-inflated
• Will not work with under-inflated tires
• 2 on the same axle
• 2 on the same car side
• All 4

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Direct TPMS Mounting Methods
Tire Wall Tire Tread Mount

Valve Stem Mount Drop Well Mount

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TPMS Architectures
• Other Direct TPMS system features in the marketplace

− Display actual individual tire pressures

− “Tire Localization”
determine location of tire on car
− “Auto-Learn”
determine tire IDs on the car
− “Initiation”
triggering a pressure reading on demand
− Motion detection to change monitoring rates
− Motion detection to save battery power when parked
− Diagnostics for manufacturing and field service

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Sensor Package Comparison

Competitor Freescale Freescale

MPXY85XX MPXY87XX
/MPXY86XX

• PG-DSOSP-14-6
• 9.24 X 11.09 X 3.9 mm

MPXY85xx/86xx smaller in size will • QFN 9x9x2.3mm

help on module’s size, weight and cost.

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 Top Level TPMS Model

Coil

LF LF
3V Motion
Receiver Signal
Batt Sensor

RF
Pressure Energy
Ant
Sensor

Controller RF
Transmitter

Temp
Sensor

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Tire Pressure Monitoring Body Receiver

Stand along TPMS display

Cluster
Infotainment
Antenna
RF
Receiver
MCU & LF
General
Control 24 psi Systems

Stand along TPMS receiver

Or RKE System Basic
MIL
Or PKE System Systems

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TPMS Roadmap
Tire Pressure
Monitoring

Nogaro Z-axis
Z axis
450/900 kPa
0.25uSGF, 2-Poly,
2 Poly, 7x7 FAM

MPXY85xx - Z-axis
450/900 kPa
0.25uSGF, 2-Poly, 9x9 Cav QFN C90FGUHV IP Blocks U-TPMS XZ-axis
450/900/1500 kPa
UMEMS Phs 4P C90FGUHV, UMEMS-4P,
UMEMS 4P, 5x5 FAM or CSP

Lausitz XZ-axis
axis
450/900 kPa
0.25uSGF, 2-Poly,
2 Poly, 7x7 FAM

Proposal
MPXY86xx - XZ-axis
450/900 kPa Lausitz XZ-axis
axis Planning
0.25uSGF, 2-Poly, 9x9 Cav QFN
Up tp 1500 kPa
0.25uSGF, 2-Poly,
2 Poly, 7x7 FAM Execution

Production
Left Edge :
First Sample Date
Right Edge :
Product Qualification

Not resourced
1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q
2013 2014 2015 2016

Preliminary schedule. To be updated by August 31, 2013

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 Tire Pressure Monitor Sensor Roadmap Change-points
Gen2 Gen3 Gen4 Gen5

Package SOIC-20 Introduce Introduce Film-Assist Eliminate Die-to-Die

Bottom-side cavity; QFN 9x9, Open top- Mold QFN 7x7 Bond wires;
4-die side cavity; 3-die 2-die
3-die
ASIC Node TSMC 250nm SGF TSMC 250nm SGF TSMC 250nm SGF Introduce 90nm TFS

ASIC Design Dedicated pressure & Muxed C-V signal Muxed C-V signal Battery-less power
inertia interfaces chains w/ Σ∆ ADC, chains w/ Σ∆ ADC, System ID, extended
( A/D & C/V ) digital filters; digital filters; BIST, & selectable
Up-integrate RF Tx Optimized LF/RF sensitivities
MEMS Nodes 2-poly inertia, 2-poly inertia & p-cell 2-poly inertia & p-cell Introduce eHARMEMS
PIDR73 pressure for pressure,
eHARMEMS inertia
MEMS Design X-lat & teeter-totter; X-lat & teeter-totter; X-lat & teeter-totter; Combined Self Test +
Redundant p-chip w/ Redundant p-cell Redundant p-cell Sense
Integrated C-V

Test Physical @ probe & Physical @ probe & Physical / Electrostatic Electrostatic @ probe
final final @ probe & final & final

Certification &/or AEC-Q100 AEC-Q100 AEC-Q100 AEC-Q100

Assessment ASIL-QM, B target

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 Competitive Positioning & Value Proposition
• Smaller in size:
− Saving on board size (customer cost benefit)
− Saving on potting material (customer cost
benefit)
− Saving on module weight (car OEM
requirement)
• Flash 8k space for customers
− 33% more space enabling a module suitable
for more car models. (inventory/operation/
production management benefit).
• Unique with dual-axis accelerometer
− enabling tire location determination without
the need for user intervention and/or the use
of LF initiator(s).
• Lower RF transmitting power
consumption
− <7mA at 5dBm
• g-cells based on technology used in
airbags we shipped close to1 billion unit
level.

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 Direct TPMS Architecture

RSM RSM

TPMS RF RSM
Receiver
SPARE

RSM RSM

RSM: Remote Sensing Module

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 Direct TPMS Architecture

RSM RSM

LF LF

TPMS RF RSM
Receiver
SPARE
LF

CAN
LF

RSM RSM

RSM: Remote Sensing Module

LF: LF Initiator

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Typical TPM Operational Parameters
Parameter Value Units
Data Measurement Interval
Motion 3 sec
Parked 15 minute
Data Transmission Interval
Motion 60 sec
Parked 60 minute
RF Transmission Protocol
Bit Rate 9600 bits/sec
Bits/Frame 90 bits
Frames/Datagram 4 frames
Pressure Change Alert 256 frames
Diagnostic Modes 6 modes
Pressure Change Alert 15 kPa
Pressure Measure Range 100 to 900 kPa
Temperature Measure Range -40 to +125 °C

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Example TPM Operational Profile

10 Years (87600 hrs)

25000 km/yr Moving (3650 hrs)

4%
decaying 1500 km/yr

Total Distance
182500 km

Average Speed of
50 km/hr
96%
Parked (83950 hrs)
Total Time Moving
3650 hrs Assume Constant
Temperature and Voltage

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Battery life and Power Consumption

Self Discharge
18% Standby
Reserve 35%
10%

16% 21%
Transmit Processing

Assume 250 mA-hr Battery

205 mA-hr used (including self-discharge)

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Measurement Uses

• Battery Voltage:
− Transmitted to car
− Helps unit determine EOL
• Temperature:
− Used to determine if device is Out Of Operation Range
• Pressure:
− Transmitted to car
− Main function of the device – determine if tires are correctly inflated
• Accelerometer(s):
− Customer IP goes into different functionalities

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Uses for acceleration

• Determine operation mode (parking/running)

• Determine wheel location
• Determine wheel position
• Determine thread’s wear
• ??

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TPMS_READ_ACCEL functionality

Zraw (counts)
Moving
Threshold

Park Mode

Time (s)
• TPMS_READ_ACCEL and TPMS_COMP_ACCEL are useful when trying
to determine whether a vehicle is moving or is stopped

• i.e. Set a threshold, determine if the threshold has been passed – Car is
moving

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TPMS_READ_ACCEL functionality

Zraw (counts)
Time (s)
• TPMS_READ_ACCEL can also be used to determine position
in the tire

• i.e. Each local maximum indicates top-most position in the tire,

each local minimum indicates bottom-most position in the tire

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TPMS_READ_ACCEL limitations

• Assume 17-inch rim (diameter = 43.18 cm; radius = 21.59 cm)

• Using centrifugal force formula

• Range, is +/- 33.9 km/h

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