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© 2022 ROHM Co., Ltd.
No. 64UG116E Rev.002
Feb.2022
User’s Guide
1.3.3
VDD_SENSOR Current Measurements
The RKX-A3-EVK-001 provides a convenient way to measure the current supplied on the VDD_SENSOR power rail for testing and evaluation
purposes. In order to measure the VDD_SENSOR current, it is recommended to remove the R64 zero-ohm resistor and to connect a current
meter across the J2 header that can be optionally populated for such a test.
Figure 8. VDD_SENSOR Current Measurement Recommended Connections
1.3.4
IO_VDD Voltage Level Shifters
The RKX-A3-EVK-001 comes with a pair of voltage level shifters (U1, U2) by default that are designated to shift the voltage levels of all digital I/O
pins from the voltage level supported by the host platform (VBUS) and I/O Voltage provided to a sensor (IO_VDD) and vice-versa (Figure 9). This
allows seamless interfacing between such platforms as the Infineon CY8CKIT-059 and Arduino UNO R3, where the I/O voltage can be as high
as 5V with many sensors that are limited to IO_VDD voltage of 3.6V or lower. Please note the following information regarding the voltage level
shifters:
⚫
The acceptable input voltage range on the host side (B-side) is 2.3V to 5.5V
⚫
The acceptable input voltage range on the device side (A-side) is 1.65V to 3.6V
⚫
There is an internal 10k pull-up resistor on each side (A and B) of the level shifter.
⚫
Level shifters have been verified to support I
2
C communication (up to 1000kHz) and SPI communication (up to 10MHz) with sensors.
For I
2
C communication, it is recommended to have additional pull-up resistors on SDA and SCL lines for faster transient switching. In
many cases, there will be pull-up resistors on the evaluation board that come with the sensor. However, in other cases, it is recommended
to populate 2.7k resistor at locations R88 (SDA) and R89 (SCL) on the RKX-A3-EVK-001. Once connected, the effective resistance
would be 2.1k on each signal level (2.7k || 10k = 2.1k), which is a sufficient value for all sensors at all VDD voltages.
⚫
It is possible to bypass the onboard level shifters if needed. This can be accomplished from removing the zero-ohm resistors on A and
B sides of the level shifter and connecting level shifter bypass resistors (R50-R57).
Figure 9. Voltage Level Shifters for I/O Signals
