SH7708 Datasheet, PDF (198/625 Pages) Renesas Technology Corp – SuperH™ RISC engine

9 . 1 1 Notes on Board Design
When Using an External Crystal Resonator: Place the crystal resonator, capacitors CL1
and CL2, and damping resistor R close to the EXTAL and XTAL pins. To prevent induction from
interfering with correct oscillation, use a common grounding point for the capacitors connected to
the resonator, and do not locate a wiring pattern near these components.
Avoid crossing
signal lines
CL1
CL2
EXTAL
R
XTAL
SH7708R
Note:The values for CL1, CL2, and the damping resistance should be determined after
consultation with the crystal manufacturer.
Figure 9.8 Points for Attention when Using Crystal Resonator
Decoupling Capacitors: As far as possible, insert a laminated ceramic capacitor of 0.01 to
0.1 µF as a passive capacitor for each V_SS/V_CC pair. Mount the passive capacitors as close as
possible to the LSI power supply pins, and use components with a frequency characteristic suitable
for the LSI operating frequency, as well as a suitable capacitance value.
Digital system V_SS/V_CC pairs: 6-7, 17-18, 19-20, 30-31, 41-42, 49-50, 54-55, 59-60, 68-69,
82-81,83, 100-102, 115-116, 121-122, 127-128, 144-139
On-chip oscillator V_SS/V_CC pairs: 73-75, 76-78, 138-135
When Using a PLL Oscillator Circuit: Keep the wiring from the PLL V_CC and V_SS
connection pattern to the power supply pins short, and make the pattern width large, to minimize
the inductance component. Ground the oscillation stabilization capacitors C1 and C2 to V_SS
(PLL1) and V_SS (PLL2), respectively. Place C1 and C2 close to the CAP1 and CAP2 pins and do
not locate a wiring pattern in the vicinity. In clock mode 7, connect the EXTAL pin to V_CC or V_SS
and leave the XTAL pin open.
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