LEA-M8S / LEA-M8T - Hardware integration manual
UBX-15030060 - R06
Product handling
Page 27 of 33
Production information
antenna. EOS causes damage to the chip structures. If the RF_IN is damaged by EOS, it is hard to
determine whether the chip structures have been damaged by ESD or EOS.
EOS protection measures
☞
For designs with GNSS positioning modules and wireless (for example, GSM/GPRS) transceivers
in close proximity, ensure sufficient isolation between the wireless and GNSS antennas. If wireless
power output causes the specified maximum power input at the GNSS RF_IN to exceed, employ
EOS protection measures to prevent overstress damage.
For robustness, EOS protection measures as shown in Figure 16 are recommended for designs
combining wireless communication transceivers (for example, GSM, GPRS) and GNSS in the same
design or in close proximity.
Small passive antennas (<2 dBic
and performance critical)
Passive antennas (>2 dBic or
performance sufficient)
Active antennas (without internal filter which
needs the module antenna supervisor circuits)
D
RF
_
IN
G
N
S
S
R
e
c
e
iv
e
r
LNA
GPS
Bandpass
Filtler
E
RF
_
IN
G
N
S
S
R
e
c
e
iv
e
r
L
GPS
Bandpass
Filtler
F
LNA with appropriate ESD rating
and maximum input power
GNSS band pass Filter: SAW or
ceramic with low insertion loss
and appropriate ESD rating
Figure 16: EOS and ESD precautions
Electromagnetic interference (EMI)
Electromagnetic interference (EMI) is the addition or coupling of energy causing a spontaneous reset
of the GNSS receiver or resulting in unstable performance. In addition to EMI degradation due to self-
jamming (see section 1.5), any electronic device near the GNSS receiver can emit noise that can lead
to EMI disturbances or damage.
The following elements are critical regarding EMI:
Unshielded connectors (for example, pin rows)
Weakly shielded lines on PCB (for example, on the top or the bottom layer and especially at the
border of a PCB)
Weak GND concept (for example, small and/or long ground line connections)
EMI protection measures are recommended when RF-emitting devices are near the GNSS receiver.
To minimize the effect of EMI, a robust grounding concept is essential. To achieve electromagnetic
robustness, follow the standard EMI suppression techniques:
http://www.murata.com/products/emc/knowhow/index.html
http://www.murata.com/products/emc/knowhow/pdf/4to5e.pdf
Improved EMI protection can be achieved by inserting a resistor or, better yet, a ferrite bead or an
inductor (see Table 8: Recommended parts
) into any unshielded PCB lines connected to the GNSS receiver. Place the resistor as close to the
GNSS receiver pin as possible.
Alternatively, feed-through capacitors with good GND connection can be used to protect, for example,
the VCC supply pin against EMI. A selection of feed-through capacitors is listed in Table 8.
