Datasheet

Electrical characteristics STM32F102x8, STM32F102xB
46/80 DocID15056 Rev 5
Note: For CL1 and CL2 it is recommended to use high-quality ceramic capacitors in the 5 pF to
15 pF range selected to match the requirements of the crystal or resonator. CL1 and CL2,
are usually the same size. The crystal manufacturer typically specifies a load capacitance
which is the series combination of CL1 and CL2.
Load capacitance CL has the following formula: CL = CL1 x CL2 / (CL1 + CL2) + C
stray
where C
stray
is the pin capacitance and board or trace PCB-related capacitance. Typically, it
is between 2 pF and 7 pF.
Caution: To avoid exceeding the maximum value of CL1 and CL2 (15 pF) it is strongly recommended
to use a resonator with a load capacitance CL ≤ 7 pF. Never use a resonator with a load
capacitance of 12.5 pF.
Example: if you choose a resonator with a load capacitance of CL = 6 pF, and Cstray = 2 pF,
then CL1 = CL2 = 8 pF.
Figure 19. Typical application with a 32.768 kHz crystal
5.3.7 Internal clock source characteristics
The parameters given in Table 24 are derived from tests performed under ambient
temperature and V
DD
supply voltage conditions summarized in Table 8.
High-speed internal (HSI) RC oscillator
ai14978b
OSC32_OU T
OSC32_IN
f
LSE
C
L1
R
F
STM32F102xx
32.768 KHz
resonator
Bias
controlled
gain
C
L2
Resonator with
integrated capacitors
Table 23. HSI oscillator characteristics
(1)
1. V
DD
= 3.3 V, T
A
= –40 to 105 °C unless otherwise specified.
Symbol Parameter Conditions Min Typ Max Unit
f
HSI
Frequency 8 MHz
DuCy
(HSI)
Duty cycle 45 55 %
ACC
HSI
Accuracy of the HSI
oscillator
User-trimmed with the RCC_CR
register
(2)
1
(3)
%
Factory-
calibrated
(4)(5)
T
A
= –40 to 105 °C –2 2.5 %
T
A
= –10 to 85 °C –1.5 2.2 %
T
A
= 0 to 70 °C –1.3 2 %
T
A
= 25 °C –1.1 1.8 %
t
su(HSI)
(4)
HSI oscillator
startup time
12µs
I
DD(HSI)
(4)
HSI oscillator power
consumption
80 100 µA