AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 58

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

3.4.2.1
Figure 3-5
3-26
a. Inverting Amplifier Configuration
Selecting a Crystal
When selecting a crystal, the load capacitance should always be specified (C
can cause variance in the oscillation frequency from the desired specified value
(resonance). The load capacitance and the loading of the feedback network have the
following relationship:
where C
the inverting amplifier and tuning these values (C
resonance. This relationship is true for both fundamental and third-overtone operation.
Finally, there is a relationship between C
amplifier, these values need to be offset with the larger load on the output (X2). Equal
values of these loads tend to balance the poles of the inverting amplifier.
The characteristics of the inverting amplifier set limits on the following parameters for
crystals:
ESR (Equivalent Series Resistance).................. 80 ohm Max
Drive Level ......................................................... 1 mW Max
The recommended range of values for C
C
C
The specific values for C
on the characteristics of the chosen crystal and board design.
Oscillator Configurations
1
2
....................................................................... 15 pF
....................................................................... 22 pF
C
1
S
is the stray capacitance of the circuit. Placing the crystal and C
Crystal
C
L
=
Note 1: Use for Third Overtone Mode
XTAL FrequencyL1 Value (Max)
20 MHz
25 MHz
33 MHz
40 MHz
(C
(C
1
1
1
+ C
and C
C
C
2
2
2
System Overview
)
)
+ C
2
must be determined by the designer and are dependent
S
8.2 H 20%
4.7 H 20%
3.0 H 20%
12 H 20%
1
and C
1
and C
2
. To enhance the oscillation of the inverting
2
1
are as follows:
, C
2
C
C
) allows the crystal to oscillate at
2
1
20%
20%
Note 1
Crystal
200 pF
b. Crystal Configuration
X1
X2
Am186ES
Microcontroller
L
in series across
L
). This value