SST89E564-40-C-PI 查看數據表（PDF） - Silicon Storage Technology
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SST89E564-40-C-PI Datasheet PDF : 58 Pages
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FlashFlex51 MCU
SST89E564 / SST89V564 / SST89E554 / SST89V554
9.6 Clock Input Options
Shown in Figure 9-2 are the input and output of an internal
inverting amplifier (XTAL1, XTAL2), which can be config-
ured for use as an on-chip oscillator.
When driving the device from an external clock source,
XTAL2 should be left disconnected and XTAL1 should be
driven.
At start-up, the external oscillator may encounter a higher
capacitive load at XTAL1 due to interaction between the
amplifier and its feedback capacitance. However, the
capacitance will not exceed 15 pF once the external signal
meets the VIL and VIH specifications.
Preliminary Specifications
9.7 Recommended Capacitor Values for
Crystal Oscillator
Crystal manufacturer, supply voltage, and other factors
may cause circuit performance to differ from one applica-
tion to another. C1 and C2 should be adjusted appropri-
ately for each design. The table below, shows the typical
values for C1 and C2 at a given frequency. If following the
satisfactory selection of all external components, the circuit
is still over driven, a series resistor, Rs, may be added.
RECOMMENDED VALUES FOR CRYSTAL OSCILLATOR
Frequency
< 8MHz
8-12MHz
>12MHz
C1 and C2
90-110pF
18-22pF
18-22pF
RS (Optional)
100Ω
200Ω
200Ω
More specific information about on-chip oscillator design
can be found in FlashFlex 51 Oscillator Circuit Design Con-
siderations Application Note.
RS
XTAL2
C2
C1
XTAL1
Vss
Using the On-Chip Oscillator
FIGURE 9-2: OSCILLATOR CHARACTERISTICS
NC
EXTERNAL
OSCILLATOR
SIGNAL
XTAL2
XTAL1
Vss
External Clock Drive
384 ILL F12.0
©2001 Silicon Storage Technology, Inc.
46
S71181-03-000 9/01 384
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