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Entry module EVK hardware user guide
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3.1.2. Power
The XE132 is powered via the USB connector J1 and/or via the pin header J3. The USB 5V power
domain supplies the USB-UART chip (U1). If the USB-UART interface is not used, a dedicated USB
charger can be used.
The XM132 module mounted on the XE132 can be powered either from a 3.3V LDO (U4) which is
supplied from the USB 5V power domain or from
“V_EXT” in the J3 pin header. V_EXT should be
between 1.8V to 3.6V. Typical value of V_EXT is 3.3V.
The power source for XM13 2 is determined by the setting of the switch “S1”. When the LED D1 on
the XE132 is lit, the XM132 is powered. If power is supplied via V_EXT and the switch S1 is in
position “V_EXT”, both t he components on XE132 and XM132 are supplied from the external power
supply.
It should be noted that regardless if “V_EXT” or “3.3V” is used to power XM132, the L ED D1 will
consume power since it is connected to “VIN”. If one wants to measure only the cu rrent consumed by
XM132, power should be supplied to XM132 via the pin “VIN_XM132” in pin header J3. In this case ,
R25 should be unmounted and S1 should be placed i n position “3.3V”. This way, all components on
XE132 are supplied from the 3.3V LDO, but XM132 is supplied from the external power supply. D1
will not indicate if XM132 is powered after R25 has been removed.
The intention of the power pin header J3 is that it can be used both for supplying power to XM132 and
for measuring current over a measurement resistor (R25). R25 is a 0 Ohm resistor, but the customer
can change it to a low-value resistor with high accuracy in order to perform very accurate
measurements of the XM132 current. See Table 3 for the pin assignment of pin header J3.
3.1.3. Not Mounted Components
As can be seen in the schematic in chapter 3.1.4, USB connector J2 and several other components are
“No Mount” . These components are related to the FTDI I2C-USB bridge chip FT4222H which can be
mounted on the PCB. It was added for internal Acconeer use, but customers are of course free to
mount these components if they wish. The I2C interface is also accessible in pin header J7. Refer to
Table 5.