Hardware Description; Overview; Configuration; Connecting Power - u-blox LEA-M8S Hardware Integration Manual

1 Hardware description

1.1 Overview

LEA-M8S and LEA-M8T are standalone GNSS positioning modules featuring the high performance u-blox M8
positioning engine. They are easy to integrate and combine exceptional positioning performance with highly
flexible power, design, and connectivity options. SMT pads allow fully automated assembly with standard pick &
place and reflow-soldering equipment for cost-efficient, high-volume production enabling short time-to-market.
For specific product features, see the LEA-M8S Data Sheet [1] and the NEO/LEA-M8T Data Sheet [2].
To determine which u-blox product best meets your needs, see the product selector tables on the u-blox
website.

1.2 Configuration

The configuration settings can be modified using UBX protocol configuration messages, more information see
the u-blox M8 Receiver Description Including Protocol Specification [3]. The modified settings remain effective
until power-down or reset. If these settings have been stored in BBR (Battery Backed RAM), then the modified
configuration will be retained, as long as the backup battery supply is not interrupted.
The configuration can be saved permanently in flash of the LEA-M8T receiver.

1.3 Connecting power

The LEA-M8S and LEA-M8T positioning modules have up to three power supply pins: VCC, V_BCKP and
VDD_USB.

1.3.1 VCC: Main Supply Voltage

The VCC pin provides the main supply voltage. During operation, the current drawn by the module can vary by
some orders of magnitude, especially if enabling low-power operation modes. For this reason, it is important
that the supply circuitry is able to support the peak power for a short time (see the LEA-M8S Data Sheet [1] and
the NEO/LEA-M8T Data Sheet [2] for detail specification).
When switching from backup mode to normal operation or at start-up, the LEA-M8S and LEA-M8T
modules must charge the internal capacitors in the core domain. In certain situations, this can result in a
significant current draw. For low power applications using Power Save and backup modes, it is
important that the power supply or low ESR capacitors at the module input can deliver this
current/charge.
Use a proper GND concept. Do not use any resistors or coils in the power line.

1.3.2 V_BCKP: Backup Supply Voltage

If the module supply has a power failure, the V_BCKP pin supplies the real-time clock (RTC) and battery backed
RAM (BBR). Use of valid time and the GNSS orbit data at start-up will improve the GNSS performance, i.e.
enables hot and warm starts. If no backup battery is connected, the module performs a cold start at power-up.
Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply, a
short current adjustment peak can cause high voltage drop on the pin with possible malfunctions.
If no backup supply voltage is available, connect the V_BCKP pin to VCC.
As long as the LEA-M8S / LEA-M8T module is supplied via the VCC, the backup battery is disconnected
from the RTC and the BBR to avoid unnecessary battery drain (see Figure 1). In this case, VCC supplies
power to the RTC and BBR.
UBX-13003140 - R07 Production Information
LEA-M8S / LEA-M8T - Hardware Integration Manual
Hardware description
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