mc68hc908qb4 Freescale Semiconductor, Inc, mc68hc908qb4 Datasheet - Page 215

• Manufacturer Part Number: mc68hc908qb4
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

18.11 Oscillator Characteristics
Freescale Semiconductor
Internal oscillator frequency
Trim accuracy
Deviation from trimmed Internal oscillator
External RC oscillator frequency, RCCLK
External clock reference frequencyy
RC oscillator external resistor
Crystal frequency, XTALCLK
ECFS1:ECFS0 = 00
ECFS1:ECFS0 = 01
AWU module internal RC oscillator frequency
1. Bus frequency, f
2. Factory trimmed to provided 12.8MHz accuracy requirement (± 5%, @25°C) for forced monitor mode communication. User
3. Values are based on characterization results, not tested in production.
4. Deviation values assumes trimming in target application @25°C and midpoint of voltage range, for example 5.0 V for 5 V
5. No more than 10% duty cycle deviation from 50%.
6. When external oscillator clock is greater than 1MHz, ECFS1:ECFS0 must be 00 or 01
7. Use fundamental mode only, do not use overtone crystals or overtone ceramic resonators
8. Due to variations in electrical properties of external components such as, ESR and Load Capacitance, operation above
9. Do not use damping resistor when ECFS1:ECFS0 = 00 or 10
10. Consult crystal vendor data sheet.
ICFS1:ICFS0 = 00
ICFS1:ICFS0 = 01
ICFS1:ICFS0 = 10 (not allowed if V
4, 8, 12.8MHz, V
4, 8, 12.8MHz, V
V
V
V
V
ECFS1:ECFS0 = 00 ( V
ECFS1:ECFS0 = 00
ECFS1:ECFS0 = 01
ECFS1:ECFS0 = 10
Feedback bias resistor
Crystal load capacitance
Crystal capacitors
Crystal series damping resistor
Feedback bias resistor
Crystal load capacitance
Crystal capacitors
DD
DD
DD
DD
f
f
f
should trim in-circuit to obtain the most accurate internal oscillator frequency for his application.
± 10% operation.
16 MHz is not guaranteed for all crystals or ceramic resonators. Operation above 16 MHz requires that a Negative Resis-
tance Margin (NRM) characterization and component optimization be performed by the crystal or ceramic resonator vendor
for every different type of crystal or ceramic resonator which will be used. This characterization and optimization must be
performed at the extremes of voltage and temperature which will be applied to the microcontroller in the application. The
NRM must meet or exceed 10x the maximum ESR of the crystal or ceramic resonator for acceptable performance.
OSCXCLK
OSCXCLK
OSCXCLK
≥ 4.5V
< 4.5V
= 5 V
= 3 V
= 1 MHz
= 4 MHz
= 8 MHz
(2)(3)
DD
DD
Characteristic
(10)
(10)
OP
(9)
(9)
± 10%, 0 to 70°C
± 10%, –40 to 125°C
, is oscillator frequency divided by 4.
DD
(10)
(10)
(1)
(1)(7)(8)
≥ 4.5 V)
(3)
(1)(5)(6)
DD
<2.7V)
(3)(4)
(1)(3)
MC68HC908QB8 Data Sheet, Rev. 2
Δ
Δ
f
f
Symbol
OSCXCLK
OSCXCLK
TRIM_ACC
f
INT_TRIM
f
f
INTCLK
C
C
RCCLK
R
INTRC
R
R
R
C
1
C
1
EXT
,C
,C
B
S
B
L
L
2
2
Min
30
—
—
—
—
—
—
dc
dc
—
—
—
—
—
—
—
—
—
—
2
8
8
1
See
See
(2 x C
(2 x C
Figure 18-7
Figure 18-8
± 0.4
12.8
Typ
L
± 2
20
20
10
18
32
—
—
—
—
L
4
8
1
0
5
) –10 pF
) – 5pF
Oscillator Characteristics
Max
100
± 5
10
32
16
32
16
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
8
MHz
MHz
MHz
MHz
MHz
MHz
Unit
kHz
kHz
MΩ
MΩ
kΩ
kΩ
kΩ
pF
pF
pF
pF
—
%
%
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