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NEO-M8L - Hardware integration manual
UBX-16010549 - R08
Hardware description
Page 7 of 28
C1-Public
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.
In USB self-powered mode, 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, that
is, VBUS is not supplied.
☞
USB bus-powered mode is not supported.
Module
VDD_USB
LDO
VDD_USB
R4
USB_DP
USB_DM
R5
C24
C23
D2
VBUS
DP
DM
GND
U
S
B
D
e
v
ic
e
C
o
n
n
e
c
to
r
U1
EN
R11
EN
Figure 2: 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 GNSS receiver is
operated as a USB self-powered device.
C23,
C24
Capacitors
Required according to the specification of LDO U1.
D2
Protection diodes Protect circuit from overvoltage /
ESD when connecting.
Use low-capacitance ESD protection such as ST
Microelectronics USBLC6-2.
R4, R5 Serial termination
resistors
Establish a full-speed driver
impedance of 28…44
A value of 27
is recommended.
R11
Resistor
100 k
is recommended for USB self-powered setup.
Table 1: Summary of USB external components
1.4.3
Display Data Channel (DDC)
An I2C-compatible Display Data Channel (DDC) interface is available with a NEO-M8L module for serial
communication with an external host CPU. The interface only supports operation in slave mode
(master mode is not supported). The DDC protocol and electrical interface are fully compatible with
the fast mode of the I2C industry standard. DDC pins SDA and SCL have internal pull-up resistors.
For more information about the DDC implementation, see the u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification [4]. For timing, parameters consult the I2C-bus
specification [9].
☞
The NEO-M8L DDC interface supports serial communication with u-blox cellular modules. See the
specification of the applicable cellular module to confirm compatibility.
1.4.4
SPI
An SPI interface is available for communication to a host CPU.
