SST89E554 SST [Silicon Storage Technology, Inc], SST89E554 Datasheet - Page 46

• Manufacturer Part Number: SST89E554
• Description: FlashFlex51 MCU
• Manufacturer: SST [Silicon Storage Technology, Inc]

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 V
©2001 Silicon Storage Technology, Inc.
FIGURE
IL
and V
9-2: O
Using the On-Chip Oscillator
IH
specifications.
SCILLATOR
C 2
C 1
C
R S
HARACTERISTICS
XTAL2
XTAL1
Vss
SST89E564 / SST89V564 / SST89E554 / SST89V554
46
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.
R
More specific information about on-chip oscillator design
can be found in FlashFlex 51 Oscillator Circuit Design Con-
siderations Application Note.
ECOMMENDED VALUES FOR CRYSTAL OSCILLATOR
Frequency
OSCILLATOR
8-12MHz
>12MHz
< 8MHz
EXTERNAL
External Clock Drive
SIGNAL
NC
C1 and C2
90-110pF
18-22pF
18-22pF
Preliminary Specifications
XTAL2
XTAL1
Vss
FlashFlex51 MCU
384 ILL F12.0
S71181-03-000 9/01
R
S
(Optional)
100
200
200
384