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NEO-5
-
Hardware
Integration
Manual
Preliminary
Design-In
GPS.G5-MS5-08003-A2
u-blox
proprietary
Page 12
your position is our focus
In
order
to
comply
with
USB
specifications,
VBUS
must
be
connected
through
an
LDO
(U1)
to
pin
VDD_USB
of
the
module.
If
the
USB
device
is
self-powered
it
is
possible
that
the
power
supply
(VCC)
is
shut
down
and
the
Baseband-IC
core
is
not
powered.
Since
VBUS
is
still
available,
it
still
would
be
signaled
to
the
USB
host
that
the
device
is
present
and
ready
to
communicate.
This
is
not
desired
and
thus
the
LDO
(U1)
should
be
disabled
using
the
enable
signal
(EN)
of
the
VCC-LDO
or
the
output
of
a
voltage
supervisor.
Depending
on
the
characteristics
of
the
LDO
(U1)
it
is
recommended
to
add
a
pull-down
resistor
(R11)
at
its
output
to
ensure
VDD_USB
is
not
floating
if
LDO
(U1)
is
disabled
or
the
USB
cable
is
not
connected
i.e.
VBUS
is
not
supplied.
If
the
device
is
bus-powered
,
LDO
(U1)
does
not
need
an
enable
control.
lists
the
present
availability
of
USB
on
NEO-5
modules.
Check
the
CFG_COM0
configuration
pin
to
select
between
Self
and
Bus
Powered
modes.
Note
that
BUS
Powered
mode
is
not
at
this
time
supported.
For
more
information
on
configuration
see
the
NEO-5 Data Sheet
Bus Powered
Self Powered
NEO-5Q
P
•
NEO-5M
P
•
•
=
Supported
P
=
Planned
availability
Q1/09
Table 2: USB availability on NEO-5 modules
Module
VDD_USB
LDO
VDD_USB
R4
USB_DP
USB_DM
R5
C24
C23
D2
VBUS
DP
DM
GND
US
B Devi
ce
C
o
nn
ect
o
r
U1
EN
R11
EN
Figure 3: USB Interface
Name
Component
Function
Comments
U1
LDO
Regulates
VBUS
(4.4
…5.25
V)
down
to
a
voltage
of
3.3
V).
Almost
no
current
requirement
(~1
mA)
if
the
GPS
receiver
is
operated
as
a
USB
self-powered
device,
but
if
bus-powered
LDO
(U1)
must
be
able
to
deliver
the
maximum
current
of
~150
mA.
A
low-cost
DC/DC
converter
such
as
LTC3410
from
Linear
Technology
may
be
used
as
an
alternative.
C23,
C24
Capacitors
Required
according
to
the
specification
of
LDO
U1
D2
Protection
diodes
Protect
circuit
from
overvoltage
/
ESD
when
connecting.
R4,
R5
Serial
termination
resistors
Establish
a
full-speed
driver
impedance
of
28…44
Ohms
A
value
of
27
Ohms
is
recommended.
R11
Resistor
Ensures
stable
signal
at
VDD_USB.
Table 3: Summary of USB external components