Information

Electrical characteristics STM32F20xxx
90/178 DocID15818 Rev 11
Note: For information on electing the crystal, refer to the application note AN2867 “Oscillator
design guide for ST microcontrollers” available from the ST website www.st.com.
Figure 33. Typical application with a 32.768 kHz crystal
6.3.9 Internal clock source characteristics
The parameters given in Table 32 and Table 33 are derived from tests performed under
ambient temperature and V
DD
supply voltage conditions summarized in Table 14.
High-speed internal (HSI) RC oscillator
Table 31. LSE oscillator characteristics (f
LSE
= 32.768 kHz)
(1)
1. Guaranteed by design, not tested in production.
Symbol Parameter Conditions Min Typ Max Unit
R
F
Feedback resistor - 18.4 - MΩ
I
DD
LSE current consumption - - 1 µA
g
m
Oscillator Transconductance 2.8 - - µA/V
t
SU(LSE)
(2)
2. t
SU(LSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized
32.768 kHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary
significantly with the crystal manufacturer
startup time V
DD
is stabilized - 2 - s
ai17531
OSC32_OUT
OSC32_IN
f
LSE
C
L1
R
F
STM32F
32.768 kHz
resonator
Resonator with
integrated capacitors
Bias
controlled
gain
C
L2
Table 32. 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 - 16 - MHz
ACC
HSI
Accuracy of the HSI
oscillator
User-trimmed with the RCC_CR
register
(2)
--1%
Factory-
calibrated
T
A
= –40 to 105 °C –8 - 4.5 %
T
A
= –10 to 85 °C –4 - 4 %
T
A
= 25 °C –1 - 1 %
t
su(HSI)
(3)
HSI oscillator
startup time
-2.24 µs
I
DD(HSI)
HSI oscillator
power consumption
-6080µA