NINA-B1 series - System integration manual
UBX-15026175 - R16
Design-in
Page 42 of 63
C1-Public
3.4
Supply interfaces
3.4.1
Module supply design
Good connection of the module’s VCC pin with DC supply source is required for correct RF
performance. The guidelines are summarized below:
•
The VC5C connection must be as wide and short as possible.
•
The VCC connection must be routed through a PCB area separated from sensitive analog signals
and sensitive functional units. It is a good practice to interpose at least one layer of PCB ground
between VCC track and other signal routing.
There is no strict requirement of adding bypass capacitance to the supply net close to the module.
But depending on the layout of the supply net and other consumers on the same net, bypass
capacitors might still be beneficial. Though the GND pins are internally connected, connect all the
available pins to solid ground on the application board, as a good (low impedance) connection to an
external ground can minimize power loss and improve RF and thermal performance.
3.5
Data communication interfaces
3.5.1
Asynchronous serial interface (UART) design
The layout of the UART bus should be done so that noise injection and cross talk are avoided.
It is recommended to use the hardware flow control with RTS/CTS to prevent temporary UART buffer
overrun.
•
If CTS is 1, then the Host/Host Controller is allowed to send.
•
If CTS is 0, then the Host/Host Controller is not allowed to send.
3.5.2
Serial peripheral interface (SPI)
The layout of the SPI bus should be done so that noise injection and cross talk are avoided.
3.5.3
I
2
C interface
The layout of the I
2
C bus should be done so that noise injection and cross talk are avoided.
3.6
NFC interface
⚠
Ensure that the NFC pins are configured correctly. Connecting an NFC antenna to the pins
configured as GPIO will damage the module.
The NFC antenna coil must be connected differentially between NFC1 and NFC2 pins of the device.
Two external capacitors should be used to tune the resonance of the antenna circuit to 13.56 MHz.
The required tuning capacitor value is given by the below equations: An antenna inductance of Lant =
2
μ
H will give tuning capacitors in the range of 130 pF on each pin. For good performance, match the
total capacitance on NFC1 and NFC2.
The NINA-B1 modules have been tested with a 3x3 cm PCB trace antenna, so it is recommended to
keep an antenna design close to these measurements. You can still use a smaller or larger antenna if
it is tuned to resonate at 13.56 MHz. To comply with European regulatory demands, the NFC antenna
must be placed in such a way that the space between the NINA-B1 module and the remote NFC
transmitter is always within 3 meters during transmission.
