Ublox EVK-NORA-B1, User Manual

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EVK-NORA-B1 - User guide
UBX-20030319 - R06 Hardware description Page 7 of 31
C1-Public
2 Hardware description
Design files in Altium, PDF, and Gerber formats for EVK-NORA-B1 PCBs may be requested from your
local
u-blox support team .
2.1 Power
EVK-NORA-B1 has six possible power sources, as described below:
Number Source Description Minimum Typical Max
1 V5DEBUG Power to debug interface USB port 3.8 VDC 5.0 VDC 5.5 VDC
2 VMODUSB Power to NORA-B1 USB interface 3.8 VDC 5.0 VDC 5.5 VDC
3 Li-Po header J26 battery connector 3.8 VDC 5.5 VDC
4 Arduino VIN J27 or J9 3.8VDC 5.5 VDC
5 CR2032 battery BAT1 coin cell holder 1.7 VDC 3.0 VDC 3.6 VDC
6 External connector J17 1.7 VDC 3.3 VDC 3.6 VDC
Table 2: EVK power sources
Power sources 1 through 4 are connected through Maxim MAX4T ideal protection diodes 1
to create VBUS_H , allowing selection of the highest input voltage.
VDD (3.3 VDC) is generated from VBUS_H . VDD , and power sources 5 and 6, are connected through
ideal protection diodes to create VBUS from the highest voltage of these three sources.
☞
The debug interface and associated level shifters are only enabled when V5DEBUG is present.
Otherwise, the debug interface is held in reset and level shifters disabled to conserve system
power.
⚠
Normally open, 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 disabled by soldering across
any of these jumpers.
For details regarding measuring current, see Current sensing headers .
2.1.1 Low-voltage mode
☞
The HV mode switch, SW1, in the schematic is labeled “Module power” on the silk screen.
With the power switch in the ON position, and the HV mode switch in the LV (low-voltage) position,
NORA-B1 is powered by
VMOD . The following power signals are active:
• VDD , sourced by 3.3V LDO = debug interface power and reference voltage. Level shifters are used
to allow independent NORA-B1 I/O voltage settings
•
VSYS , sourced by VBUS = EVK system power
• VSHLD , sourced by VSYS = power source for shields connected through the Arduino header, J27
and J9
• VMOD , sourced by VSYS = NORA-B1 VDD module power input and I/O reference voltage
•
VMODH , sourced by VMOD = NORA-B1 VDDH module power input (bypass NORA-B1 HV LDO)
⚠
Only if the power protection circuits are left intact can USB be safely connected at the same time
as the coin cell or external power. This allows programming of the module while leaving other power
sources connected.
1 Maxim MAX4T ideal protection diodes provide maximum forward voltage drop of 28 mV at 100 mA and prevent
reverse current flow to other connected supplies.