Datasheet
Table Of Contents
- Document Information
- Contents
- 1 Functional description
- 1.1 Overview
- 1.2 Product features
- 1.3 Performance
- 1.4 Block diagram
- 1.5 Supported GNSS Constellations
- 1.6 Assisted GNSS (A-GNSS)
- 1.7 Augmentation Systems
- 1.8 Broadcast Navigation Data
- 1.9 Untethered Dead Reckoning (UDR)
- 1.10 Odometer
- 1.11 Data logging
- 1.12 Geofencing
- 1.13 Message Integrity Protection
- 1.14 Spoofing Detection
- 1.15 TIMEPULSE
- 1.16 Protocols and interfaces
- 1.17 Interfaces
- 1.18 Clock generation
- 1.19 Power management
- 1.20 Antenna
- 2 Pin Definition
- 3 Configuration management
- 4 Electrical specification
- 5 Mechanical specifications
- 6 Reliability tests and approvals
- 7 Product handling & soldering
- 8 Default messages
- 9 Labeling and ordering information
- Related documents
- Revision history
- Contact
NEO-M8U - Data Sheet
UBX-15015679 - R06 Functional description Page 13 of 27
Product Information
1.18.2 Real-Time Clock (RTC) and Hardware Backup mode
The RTC can be maintained by a secondary 32 kHz oscillator using an RTC crystal. If the main supply
voltage is removed, a battery connected to V_BCKP allows the RTC to continue to run with very low
power consumption. The same supply also maintains a static back-up memory for current
configuration information, recent ephemeris, location and auxiliary data necessary to ensure the
fastest re-acquisition when the primary power supply is restored.
☞ Dead-reckoning before the first GNSS fix requires that the RTC has been enabled and powered
since the previous fix.
1.19 Power management
u-blox M8 technology offers a power-optimized architecture with built-in autonomous power saving
functions to minimize power consumption at any given time. In addition, a high efficiency DC/DC
converter is integrated for lower power consumption and reduced dissipation.
1.19.1 Power control
A separate battery backup voltage may be applied to the module to retain the current state of the
receiver and sustain a low power real time clock (RTC) while the main supply is removed. This enables
fast acquisition and navigation based on dead-reckoning before the first GNSS-based fix.
Alternatively, a configuration command (UBX-CFG-PWR) can be issued to stop the receiver in a similar
way to Hardware Backup Mode (see section 1.18.2) while the main supply remains active. This mode
is referred to as Software backup mode; current consumption in this mode is slightly higher than in
Hardware Backup Mode. The receiver will then restart on the next edge received at its UART interface
(there will be a delay before any communications are possible).
See Table 10 for current consumption in backup mode.
1.20 Antenna
u-blox recommend use of an active antenna
12
or external LNA with this module to achieve best
performance.
Parameter Specification
Antenna Type Active or passive antenna
Active Antenna Recommendations Minimum gain
Maximum gain
Maximum noise figure
15 dB (to compensate signal loss in RF cable)
50 dB
13
1.5 dB
Table 5: Antenna Specifications for the NEO-M8U module
The antenna system should include filtering to ensure adequate protection from nearby transmitters.
Care should be taken in the selection of antennas placed closed to cellular or Wi-Fi transmitting
antennas.
☞ For guidance on antenna selection see the NEO-M8U Hardware Integration Manual [1].
12
For information on using active antennas with NEO-M8U modules, see the
NEO-M8U Hardware Integration Manual [1]
.
13
Gain above 20 dB should be avoided unless interference in the band 1463 MHz to 1710 MHz is adequately controlled.