Table of Contents
Advertisement
LEA-M8S / LEA-M8T - Hardware Integration Manual
Figure 1: Backup battery and voltage (for exact pin orientation, see the LEA-M8S Data Sheet [1] and the NEO/LEA-M8T Data
Sheet [2])
1.3.3 VDD_USB: USB interface power supply
VDD_USB supplies the USB interface. If the USB interface is not used, the VDD_USB pin must be connected to
GND. For more information about correctly handling the VDD_USB pin, see section 1.4
1.3.4 VCC_RF: Output Voltage RF section
The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 2.4.
1.3.5 V_ANT: Antenna supply
The V_ANT pin is available to provide antenna bias voltage to supply an optional external active antenna. For
more information, see section 2.4.
If not used, connect the V_ANT pin to GND.
1.4 Interfaces
1.4.1 UART
The LEA-M8S and LEA-M8T positioning modules include a Universal Asynchronous Receiver Transmitter (UART)
serial interface RxD/TxD, which supports configurable baud rates. The baud rates supported are specified in the
LEA-M8S Data Sheet [1] and the NEO/LEA-M8T Data Sheet [2]. The signal output and input levels are 0 V to
VCC. An interface based on RS232 standard levels (+/- 12 V) can be implemented using level shifters such as
Maxim MAX3232. Hardware handshake signals and synchronous operation are not supported.
1.4.2 USB
A USB version 2.0 FS (Full Speed, 12 Mb/s) compatible interface is available for communication as an alternative
to the UART. The USB_DP integrates a pull-up resistor to signal a full-speed device to the host. The VDD_USB
pin supplies the USB interface.
u-blox provides Microsoft® certified USB drivers for Windows Vista, and Windows 7 operating systems (also
Windows 8 compatible). These drivers are available at our website at www.u-blox.com
USB external components
The USB interface requires some external components to implement the physical characteristics required by the
USB 2.0 specification. These external components are shown in Figure 2 and listed in Table 1. To comply with
USB specifications, VBUS must be connected through an LDO (U1) to pin VDD_USB on the module.
The USB device is self-powered, the power supply (VCC) can be turned off and the digital block is not
powered. In this case, since VBUS is still available, the USB host would still receive the signal indicating that the
device is present and ready to communicate. This should be avoided by disabling the LDO (U1) 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 the
LDO (U1) is disabled or the USB cable is not connected, i.e. VBUS is not supplied.
UBX-13003140 - R07
Production Information
Hardware description
Page 5 of 31
Advertisement
Table of Contents
