RL78/G14
Recommended PCB Layout for Reducing Noise
5. Improve the Non-recommended Board
After the above test, modifications were made on the non-recommended board and retested under the same conditions.
In this test, the non-recommended PCB board was modified provisionally to improve reducing noise performance.
When developing a product, the PCB layout should be redesigned according to the recommended layout for high
performance.
5.1
Modification of the Non-recommended Board
Modified items are listed below:
•
VDD and VSS: Remove J1 and connect the MCU VDD to C9 with a jumper line to modify the VDD wiring
connection. Cutoff the VSS wiring of oscillator circuit and reset circuit to modify the VSS connection. Refer to the
red section in Figure 5.1.
•
Oscillator concerns: Cutoff the original wiring which connects the VSS of oscillator circuit to the MCU VSS pin.
Connect them with a jumper to shorten the VSS wiring of the oscillator circuit. Refer to the orange section in the
Figure 5.1.
•
Bypass capacitor: Move C4 close to the MCU. Refer to the violet section in the Figure 5.1.
•
Reset circuit: Cutoff the original wiring of reset circuit which connects to the VDD and VSS. Connect these
components (R1, D1, C6) to the MCU VDD and VSS with jumper lines. Refer to the blue section in the Figure 5.1.
•
REGC circuit: Move C3 close to the MCU. Refer to the gold section in the Figure 5.1.
•
TOOL0 circuit: Move R2 close to the MCU. Refer to the green section in the Figure 5.1.
Figure 5.1 Improving the Non-recommended Board
R01AN1876EC0100 Rev. 1.00
Page 12 of 14
Feb. 28, 2014
