MC68HC908QC16_07 Datasheet, PDF (244/274 Pages) Freescale Semiconductor, Inc – Microcontrollers

Electrical Specifications
Characteristic
Symbol
Min
Typ
Max
Unit
RC oscillator external resistor
V_DD = 5 V
V_DD = 3.3 V
R_EXT
See Figure 19-7
—
See Figure 19-8
Crystal frequency, XTALCLK ^{(1) (7) (8)}
ECFS1:ECFS0 = 00 (V_DD ≥ 4.5 V)
ECFS1:ECFS0 = 00
ECFS1:ECFS0 = 01
ECFS1:ECFS0 = 10
8
f_OSCXCLK
8
1
30
—
32
MHz
—
16
MHz
—
8
MHz
—
100
kHz
ECFS1:ECFS0 = 00⁽⁹⁾ (f_OSCXCLK: 8–32 MHz)
Feedback bias resistor
Crystal load capacitance⁽¹⁰⁾
Crystal capacitors⁽¹⁰⁾
R_B
—
1
—
MΩ
C_L
—
20
—
pF
C₁, C₂
—
(2 x C_L) – 5pF
—
pF
ECFS1:ECFS0 = 01⁽⁹⁾ (f_OSCXCLK: 1–8 MHz)
Crystal series damping resistor
f_OSCXCLK = 1 MHz
f_OSCXCLK = 4 MHz
f_OXCSCLK = 8 MHz
Feedback bias resistor
Crystal load capacitance⁽¹⁰⁾
Crystal capacitors⁽¹⁰⁾
R_S
—
20
—
kΩ
—
10
—
kΩ
—
0
—
kΩ
R_B
—
5
—
MΩ
C_L
—
18
—
pF
C₁, C₂
—
(2 x C_L) –10pF
—
pF
ECFS1:ECFS0 = 10⁽⁹⁾ (f_OSCXCLK: 30–100 kHz)
Feedback bias resistor
Crystal load capacitance⁽¹⁰⁾
Crystal capacitors⁽¹⁰⁾
R_B
—
10
—
MΩ
C_L
—
12.5
—
pF
C₁, C₂
—
(2 x C_L) –10
—
pF
PWU module Internal RC oscillator frequency
f_INTRC
—
32
—
kHz
1. Bus frequency, f_OP, is oscillator frequency divided by 4.
2. Factory trimmed to provided 12.8MHz accuracy requirement (± 5%, @ 25°C and V_DD = 5.0 V) for forced monitor mode
communication. User should trim in-circuit to obtain the most accurate internal oscillator frequency for his application.
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 ± 10% operation.
5. No more than 10% duty cycle deviation from 50%.
6. When external oscillator clock is greater than 1 MHz, 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
16 MHz is not guaranteed for all crystals or ceramic resonators. Operation above 16 MHz requires that a Negative
Resistance 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.
9. Do not use damping resistor when ECFS1:ECFS0 = 00 or 10.
10. Consult crystal vendor data sheet.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 3
244
Freescale Semiconductor