u-blox EVK-NORA-B1, Руководство пользователя

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EVK-NORA-B1 - User guide
UBX-20030319 - R05 Hardware description Page 6 of 32
C1-Public
2 Hardware description
Design files for the EVK-NORA-B1 PCB may be requested from your local u-blox support team .
2.1 Power
The EVK-NORA-B1 has five possible power sources, as listed below:
•
USB from the debug interface
•
USB peripheral on the NORA-B1 itself
•
CR2032 coin cell battery
•
2.54 mm through-hole connector for connecting 3.3 V
•
Lithium Polymer (LiPo) battery input
These power sources use Maxim MAX4T ideal protection diodes with a maximum voltage
drop of 28 mV at 100 mA to prevent reverse voltage to any supply. This allows them to be used
simultaneously with the highest voltage supply being selected. Solder jumpers are provided to allow
by-passing any of the protection diodes.
⚠
Care should be taken not to damage the supplies when the protection is by-passed.
2.1.1 Powering the board
During typical debugging, power is provided by VBUS on the USB debug interface that supplies 5 V to
the 3.3 V LDO regulator and shield connector. The LDO regulator powers the
VIO
,
VSHLD
, and
VBMD
power rails.
When powering the board from the CR2032 coin cell (3 VDC), the external power header, or LiPo
header, the debug interface USB port can be left disconnected. In this configuration, the debug
interface IC is held in reset to conserve power.
⚠
Only if the power protection circuits are left intact can the USB be safely connected at the same
time as the coin cell or external power. This makes programming of the module easier.
2.1.2 USB peripheral power
By moving the HV mode switch SW1 to the HV setting, VBUS power from the USB Peripheral interface
can be used to power the EVK-NORA-B1.
The HV setting enables the internal high-voltage regulator (LDO or DC-DC) on the module.