ST72325 STMICROELECTRONICS [STMicroelectronics], ST72325 Datasheet - Page 150

• Manufacturer Part Number: ST72325
• Description: 8-BIT MCU WITH 16 TO 60K FLASH/ROM, ADC, CSS, FIVE TIMERS, SPI, SCI, I2C INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72325
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 are based
on characterization results with specified typical
external components. In the application, the reso-
nator and the load capacitors have to be placed as
Figure 76. Typical Application with a Crystal or Ceramic Resonator
Notes:
1. The oscillator selection can be optimized in terms of supply current using an high quality resonator with small R
Refer to crystal/ceramic resonator manufacturer for more details.
2. Data based on characterisation results, not tested in production.
3. The relatively low value of the RF resistor, offers a good protection against issues resulting from use in a humid envi-
ronment, due to the induced leakage and the bias condition change. However, it is recommended to take this point into
account if the µC is used in tough humidity conditions.
3. For C
for high-frequency applications and selected to match the requirements of the crystal or resonator. C
ally the same size. The crystal manufacturer typically specifies a load capacitance which is the series combination of C
and C
mate of the combined pin and board capacitance).
150/193
f
R
C
C
i
2
OSC
Symbol
Symbol
F
L1
L2
WHEN RESONATOR WITH
INTEGRATED CAPACITORS
L2
. PCB and MCU pin capacitance must be included when sizing C
L1
and C
Oscillator Frequency
Feedback resistor
Recommended load capacitance ver-
sus equivalent serial resistance of the
crystal or ceramic resonator (R
OSC2 driving current
L2
it is recommended to use high-quality ceramic capacitors in the 5-pF to 25-pF range (typ.) designed
Parameter
C
L2
Parameter
C
L1
2)
1)
RESONATOR
V
f
f
f
f
OSC
OSC
OSC
OSC
DD
S
)
3)
=5V:
OSC1
OSC2
= 2MHz, C0 = 6pF, Cl1 = Cl2 = 68pF
= 4MHz, C0 = 6pF, Cl1 = Cl2 = 68pF
= 8MHz, C0 = 6pF, Cl1 = Cl2 = 40pF
= 16MHz, C0 = 7pF, Cl1 = Cl2 = 20pF
f
f
f
f
OSC
OSC
OSC
OSC
R
= 1 to 2 MHz
= 2 to 4 MHz
= 4 to 8 MHz
= 8 to 16 MHz
Conditions
F
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...).
V
Ref
DD
Conditions
/2
i
AMPLIFIER
2
L1
LINEAR
and C
L2
(10 pF can be used as a rough esti-
f
OSC
FEEDBACK
LOOP
Min
Typ
20
20
20
15
15
426
425
456
660
1
ST72XXX
POWER DOWN
LOGIC
L1
Max
Max
and C
16
40
60
50
35
35
L2,
are usu-
S
MHz
Unit
Unit
kΩ
pF
value.
µA
L1