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
fOSC
RF
CL1
CL2
Parameter
Oscillator Frequency 1)
Feedback resistor2)
Recommended load capacitance ver-
sus equivalent serial resistance of the
crystal or ceramic resonator (RS)3)
Conditions
fOSC= 1 to 2 MHz
fOSC= 2 to 4 MHz
fOSC= 4 to 8 MHz
fOSC= 8 to 16 MHz
Min
Max
Unit
1
16
MHz
20
40
kΩ
20
60
20
50
15
35
pF
15
35
Symbol
Parameter
i2
OSC2 driving current
Conditions
VDD=5V:
fOSC= 2MHz, C0 = 6pF, Cl1 = Cl2 = 68pF
fOSC= 4MHz, C0 = 6pF, Cl1 = Cl2 = 68pF
fOSC= 8MHz, C0 = 6pF, Cl1 = Cl2 = 40pF
fOSC= 16MHz, C0 = 7pF, Cl1 = Cl2 = 20pF
Typ Max
426
425
456
660
Unit
µA
Notes:
1. The oscillator selection can be optimized in terms of supply current using an high quality resonator with small RS value.
Refer to crystal/ceramic resonator manufacturer for more details.
2. Data based on characterisation results, not tested in production.
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