z8f1621 ZiLOG Semiconductor, z8f1621 Datasheet - Page 223

• Manufacturer Part Number: z8f1621
• Description: High Performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

Oscillator Operation with an External RC Network
PS019921-0308
Figure 40. Connecting the On-Chip Oscillator to an External RC Network
The External RC oscillator mode is applicable to timing insensitive applications.
Figure 40
capacitor (RC) network.
An external resistance value of 45 kΩ is recommended for oscillator operation with an
external RC network. The minimum resistance value to ensure operation is 40 kΩ. The
typical oscillator frequency can be estimated from the values of the resistor (R in kΩ) and
capacitor (C in pF) elements using the following equation:
Figure 41
capacitor (C in pF) employed in the RC network assuming a 45 kΩ external resistor. For
very small values of C, the parasitic capacitance of the oscillator XIN pin and the printed
circuit board should be included in the estimation of the oscillator frequency.
It is possible to operate the RC oscillator using only the parasitic capacitance of the pack-
age and printed circuit board. To minimize sensitivity to external parasitics, external
capacitance values in excess of 20 pF are recommended.
Oscillator Frequency (kHz)
displays a recommended configuration for connection with an external resistor-
displays the typical (3.3 V and 25 °C) oscillator frequency as a function of the
V
DD
=
R
C
-------------------------------------------------------- -
(
0.4
×
R
X
IN
1
×
×10
C
)
6
+
(
4
×
C
)
Z8 Encore! XP
Product Specification
®
On-Chip Oscillator
F64XX Series
209