SH7108 Datasheet, PDF (92/560 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 4 Clock Pulse Generator
When using a crystal resonator, place the crystal resonator and its load capacitors as close as
possible to the XTAL and EXTAL pins. Do not route any signal lines near the oscillator circuitry
as shown in figure 4.5. Otherwise, correct oscillation can be interfered by induction.
Avoid
C_L2
Signal A Signal B
This LSI
XTAL
EXTAL
C_L1
Figure 4.5 Cautions for Oscillator Circuit System Board Design
A circuitry shown in figure 4.6 is recommended as an external circuitry around the PLL. Place
oscillation stabilization capacitor C1 close to the PLLCAP pin, and ensure that no other signal
lines cross this line. Separate PLLVCL and PLLVSS circuit against VCC and VSS circuit from the
board power-supply source, and be sure to insert bypass capacitors CB and CPB close to the pins.
R1: 3kΩ
PLLCAP
C1: 470 pF
PLLV_CL
PLLV_SS
CPB = 0.47 μF^*
V_CC
CB = 0.47 μF^*
V_SS
(Values are recommended values.)
Note: * CB and CPB are laminated ceramic type.
Figure 4.6 Recommended External Circuitry Around the PLL
Electromagnetic waves are radiated from an LSI in operation. This LSI has an electromagnetic
peak in the harmonics band whose primary frequency is determined by the lower frequency
between the system clock (φ) and peripheral clock (Pφ). For example, when φ = 50 MHz and Pφ =
40 MHz, the primary frequency is 40 MHz. If this LSI is used adjacent to a device sensitive to
electromagnetic interference, e.g. FM/VHF band receiver, a printed circuit board of more than
four layers with planes exclusively for system ground is recommended.
Rev.1.00 Sep. 18, 2008 Page 58 of 522
REJ09B0069-0100