your position is our focus
Schematic
Leave
the
RESET_N
pin
open
if
not
used.
Don’t
drive
it
high!
Leave
BOOT_INT
pin
open
if
not
used
for
firmware
update.
Plan
use
of
2
nd
interface
for
firmware
updates
or
as
a
service
connector.
2.2 TIM-4R/LEA-4R Design
LEA-4R
TIM-4R
Odometer
Optional
Direction
Turn Rate Sensor
Filer, opto-couplers
Filer, opto-couplers
3V
levels
3V
levels
SPEED
FWD
SPI
RATE
Low-Pass
filter
(MOSI)
leave
open
Digital
Temp
Sensor
A
D
GND
RF_IN
Coaxial
connector
RF_IN
VANT
V_ANT
AADET_N
VCC_REF
V_BAT
VCC
(3V)
GND
GND
VDD18_OUT
TxD1
/ TxD2
RxD1
/ RxD2
USB
USB
TIMEPULSE
RESET_N
Optional
Optional
(BOOT_INT)
leave
open
Open
circuit
detection
(optional)
Gyro
Backup
Supply
Figure 5: Block Schematic of a complete LEA-4R / TIM-4R Design
2.2.1 Forward / Backward Indication
Use
of
the
forward
/
backward
indication
signal
FWD
is
optional
but
strongly
recommended
for
good
dead
reckoning
performance.
Connect
to
VDD18_OUT
(1.8V)
if
not
used.
You
need
to
check
the
voltage
levels
and
the
quality
of
the
vehicle
signals.
They
may
be
of
different
voltage
levels,
for
example
12V
nominal
with
a
certain
degree
of
variation.
Use
of
optocouplers
or
other
approved
EMI
protection
and
filtering
is
strongly
recommended.
2.2.2 Odometer / Speedpulses
DR
receivers
use
signals
from
sensors
in
the
car
to
establish
the
velocity
and
distance
traveled.
These
sensors
are
referred
to
as
the
odometer
and
the
signals
can
be
designated
odometer
pulses,
speedpulses,
speed
ticks,
wheel
pulses
or
wheel
ticks.
These
terms
are
often
used
interchangeably
which
can
sometimes
lead
to
confusion.
For
the
sake
of
consistency,
in
this
document
we
will
be
referring
to
these
signals
as
speedpulses.
2.2.3 Power Supply for Gyroscope, Temperature Sensor and A/D Converter
The
Gyro
and
the
A/D-Converter
are
especially
sensitive
to
voltage
drop
and
ripple.
Therefore
a
clean
power
supply
must
be
designed,
which
is,
for
example,
not
affected
from
current
spikes
produced
by
the
GPS
module.
LEA-4R
/
TIM-4R
-
System
Integration
Manual
/
Reference
Design
Design-In
GPS.G4-MS4-05043
Page 11
