MC68HC908GT16_07 Datasheet, PDF (261/292 Pages) Freescale Semiconductor, Inc – Microcontrollers

20.10 Internal Oscillator Characteristics
Internal Oscillator Characteristics
Characteristic⁽¹⁾
Symbol
Min
Typ
Max
Internal oscillator base frequency^{(2), (3)}
Internal oscillator tolerance
Internal oscillator multiplier⁽⁴⁾
f_INTOSC
230.4
307.2
384
f_{OSC_TOL}
–25
—
+25
N
1
—
127
1. V_DD = 5.5 Vdc to 2.7 Vdc, V_SS = 0 Vdc, T_A = T_A (min) to T_A (max), unless otherwise noted
2. Internal oscillator is selectable through software for a maximum frequency. Actual frequency will be
multiplier (N) x base frequency.
3. f_Bus = (f_INTOSC / 4) x N when internal clock source selected
4. Multiplier must be chosen to limit the maximum bus frequency of 4 MHz for 2.7-V operation and 8 MHz
for 4.5-V operation.
Unit
kHz
%
—
20.11 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
—
10 M
Crystal load capacitance⁽⁹⁾
Crystal fixed capacitance⁽⁹⁾
Crystal tuning capacitance⁽⁹⁾
Feedback bias resistor⁽⁹⁾
Series resistor ^(9)(10)
C_L
—
—
—
pF
C₁
—
2 x C_L
—
pF
C₂
—
2 x C_L
—
pF
R_B
—
10
—
MΩ
R_S
—
—
—
MΩ
1. V_DD = 5.5 to 2.7 Vdc, V_SS = 0 Vdc, T_A = T_A (min) to T_A (max), 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 to 16 MHz at V_DD = 2.7 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. Consult crystal vendor data sheet, see Figure 7-4. External Clock Generator Block Diagram.
10. Not required for high-frequency crystals
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
Freescale Semiconductor
261