SH7211 Datasheet, PDF (99/1228 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family

Section 4 Clock Pulse Generator (CPG)
4.6 Notes on Board Design
4.6.1 Note on Using an External Crystal Resonator
Place the crystal resonator and capacitors CL1 and CL2 as close to the XTAL and EXTAL pins as
possible. In addition, to minimize induction and thus obtain oscillation at the correct frequency,
the capacitors to be attached to the resonator must be grounded to the same ground. Do not bring
wiring patterns close to these components.
Signal lines prohibited
CL1
CL2
Reference value
CL1 = 20 pF
CL2 = 20 pF
EXTAL
XTAL
This LSI
Note:
The values for CL1 and CL2
should be determined after
consultation with the crystal
resonator manufacturer.
Figure 4.2 Note on Using a Crystal Resonator
4.6.2 Note on Bypass Capacitor
A multilayer ceramic capacitor should be inserted for each pair of Vss and Vcc as a bypass
capacitor as many as possible. The bypass capacitor must be inserted as close to the power supply
pins of the LSI as possible. Note that the capacitance and frequency characteristics of the bypass
capacitor must be appropriate for the operating frequency of the LSI.
4.6.3 Note on Using a PLL Oscillation Circuit
In the PLLVcc and PLLVss connection pattern for the PLL, signal lines from the board power
supply pins must be as short as possible and pattern width must be as wide as possible to reduce
inductive interference.
Since the analog power supply pins of the PLL are sensitive to the noise, the system may
malfunction due to inductive interference at the other power supply pins. To prevent such
malfunction, the analog power supply pin Vcc and digital power supply pin VccQ should not
supply the same resources on the board if at all possible.
Rev. 2.00 May. 08, 2008 Page 75 of 1200
REJ09B0344-0200