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© 2022 ROHM Co., Ltd.
No. 64UG116E Rev.002
Feb.2022
User’s Guide
Figure 5. RKX-A3-EVK-001 VDD Sensor Select
The VR1 voltage regulator is a variable output Low Dropout (LDO) linear voltage regulator. The output voltage of the VR1 is selected via rotary
switch SW2. The SW2 switch has 7 positions as indicated on the schematic and on the printed circuit board itself. The switch SW2 can be rotated
with a small flat screwdriver. By default, the RKX-A3-EVK-001 is shipped with switch SW2 in Position 1. See Table 2 for details on how to select
the output voltage using SW2.
Table 2. Switch SW2 Voltage Select for different Switch Positions
SW2 position
1
2
3
4
5
6
7
VR1_OUT
3.3V
(default)
3.0V
2.8V
2.5V
1.8V
1.7V
3.6V
Following the voltage path from VBUS to the switch SW1 (from left-to-right in Figure 5), next comes switch SW4 (VDD_SENSOR ON/OFF switch).
The purpose of the switch SW4 is to disconnect the VDD_SENSOR from the input voltage (VBUS). This can be useful when an evaluation board
needs to be unplugged and re-plugged again. By default, the switch SW4 is on the ON position (UP position when looked from above). When the
RKX-A3-EVK-001 is connected to a host platform, and the switch SW4 is turned ON, the orange LED (LED2) will be ON. If the switch SW1 is
connected to the output of the VR1 voltage regulator (VR1_OUT), the brightness of the orange LED will be proportional to the VR1_OUT voltage
output. At default position of the switch SW2 (3.3V) the LED light will be bright and when the output voltage is selected to 1.8V or 1.7V using the
switch SW2, the LED2 light will be dim. If the orange LED (LED2) is completely OFF and the green led (LED1) is ON, please ensure the switch
SW2 is not turned to an intermediate position and is at one of the 7 positions shown in Table 2.
