ST72321B Datasheet, PDF (146/187 Pages) STMicroelectronics – 64/44-pin 8-bit MCU with 32 to 60K Flash/ROM, ADC, five timers, SPI, SCI, I2C interface

CLOCK AND TIMING CHARACTERISTICS (Cont’d)
12.5.3 Crystal and Ceramic Resonator Oscillators
The ST7 internal clock can be supplied with four
different Crystal/Ceramic resonator oscillators. All
the information given in this paragraph is based on
characterization results with specified typical ex-
ternal components. In the application, the resona-
tor and the load capacitors have to be placed as
close as possible to the oscillator pins in order to
minimize output distortion and start-up stabiliza-
tion time. Refer to the crystal/ceramic resonator
manufacturer for more details (frequency, pack-
age, accuracy...).
Symbol
Parameter
Conditions
Min
f_OSC
R_F
C_L1
C_L2
Oscillator Frequency ¹⁾
Feedback resistor²⁾
LP: Low power oscillator
1
MP: Medium power oscillator
>2
MS: Medium speed oscillator
>4
HS: High speed oscillator
>8
20
Recommended load capacitance ver-
sus equivalent serial resistance of the
crystal or ceramic resonator (R_S)
R_S=200Ω
R_S=200Ω
R_S=200Ω
R_S=100Ω
LP oscillator 22
MP oscillator 22
MS oscillator 18
HS oscillator 15
Max
2
4
8
16
40
56
46
33
33
Unit
MHz
kΩ
pF
Symbol
Parameter
i₂
OSC2 driving current
V_DD=5V
V_IN=V_SS
Conditions
LP oscillator
MP oscillator
MS oscillator
HS oscillator
Typ
Max
Unit
80
150
160
250
310
460
µA
610
910
Notes:
1. The oscillator selection can be optimized in terms of supply current using an high quality resonator with small R_S value.
Refer to crystal/ceramic resonator manufacturer for more details.
2. Data based on characterisation results, not tested in production.
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