Z86E3016PSG Datasheet, PDF (55/348 Pages) Zilog, Inc. – Z86E3016PSG

Z8 CPU
User Manual
37
Capacitor C₂ combined with the amplifier output resistance provides a
small phase shift. It will also provide some attenuation of overtones.
Capacitor C₁ combined with the crystal resistance provides additional
phase shift.
C₁ and C₂ can affect the start-up time if they increase dramatically in size.
As C₁ and C₂ increase, the start-up time increases until the oscillator
reaches a point where it does not start up any more.
For fast and reliable oscillator start-up over the manufacturing process
range, ZiLOG recommends that the load capacitors be sized as low as
possible without resulting in overtone operation.
Z8 CPU
V_SS
A
V₁
R_I
V₀
XTAL1
C1
XTAL2
C2
Figure 16. Pierce Oscillator with Internal Feedback Circuit
Layout
Traces connecting crystal, caps, and the Z8^® CPU oscillator pins should
be as short and wide as possible. This reduces parasitic inductance and
resistance. The components (caps, crystal, resistors) should be placed as
close as possible to the oscillator pins of the Z8^® CPU .
The traces from the oscillator pins of the IC and the ground side of the
lead caps should be guarded from all other traces (clock, V_CC, address/
UM001602-0904
Clock