MC68HC908EY16 Datasheet, PDF (245/278 Pages) Motorola, Inc – Microcontrollers

20.8 External Oscillator Characteristics
External Oscillator Characteristics
Characteristic⁽¹⁾
Symbol
Min
Typ
Max
Unit
External clock option⁽²⁾⁽³⁾
With ICG clock disabled
With ICG clock enabled
EXTSLOW = 1⁽⁴⁾
EXTSLOW = 0⁽⁴⁾
dc⁽⁵⁾
—
32 M⁽⁶⁾
f_EXTOSC
Hz
60
—
307.2 k
307.2 k
—
32 M⁽⁶⁾
External crystal options⁽⁷⁾⁽⁸⁾
EXTSLOW = 1⁽⁴⁾
EXTSLOW = 0⁽⁴⁾
f_EXTOSC
30 k
1M
—
100 k
Hz
—
8M
Crystal load capacitance⁽⁹⁾
Crystal fixed capacitance⁽⁹⁾
Crystal tuning capacitance⁽⁹⁾
EXTSLOW = 1
Feedback bias resistor⁽⁹⁾
Series resistor ⁽⁹⁾
C_L
—
12.5
—
pF
C₁
—
15
—
pF
C₂
—
15
—
pF
R_B
—
10
—
MΩ
R_s
100
330
470
kΩ
EXTSLOW = 0
Feedback bias resistor⁽⁹⁾
Series resistor ^(9)(10)
f_EXTOSC = 1 MHz
f_EXTOSC = 4 MHz
f_EXTOSC = 8 MHz
R_B
—
1
—
MΩ
R_s
—
20
—
kΩ
R_s
—
10
—
kΩ
R_s
—
0
—
kΩ
1. V_DD = 4.5 to 5.5 Vdc, V_SS = 0 Vdc, T_A = –40°C to +135°C, unless otherwise noted
2. Setting EXTCLKEN configuration option enables OSC1 pin for external clock square-wave input.
3. No more than 10% duty cycle deviation from 50%
4. EXTSLOW configuration option configures external oscillator for a slow speed crystal and sets the clock monitor circuits
of the ICG module to expect an external clock frequency that is higher/lower than the internal oscillator base frequency,
f_INTOSC.
5. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this
information.
6. MCU speed derates from 32 MHz at V_DD = 4.5 Vdc
7. Setting EXTCLKEN and EXTXTALEN configuration options enables OSC1 and OSC2 pins for external crystal option.
8. f_Bus = (f_EXTOSC / 4) when external clock source is selected.
9. Crystal manufacturer’s value, see Figure 8-3. Internal Clock Generator Block Diagram.
10. Not required for high-frequency crystals
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
245